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Greenman W, Murillo FJ, de Moura Neves B, Kenchington E, Jasperse L, Fox A, Walker B, Edinger E, Sherwood O. Metre-scale vertical zonation of corals and sponges on a deep-marine cliff reflects trophic resource partitioning. Sci Rep 2025; 15:6750. [PMID: 40000672 PMCID: PMC11861900 DOI: 10.1038/s41598-025-89116-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Accepted: 02/03/2025] [Indexed: 02/27/2025] Open
Abstract
Corals and sponges are considered foundational species and can create biodiversity hotspots in the deep sea, yet little is known of their competitive interactions, particularly with respect to resource partitioning among benthic fauna. Here we report on the feeding ecology of deep-water corals, sponges, ascidians, and anemones from a ~ 450 m deep submarine canyon wall off Nova Scotia, Canada. Analysis of bulk stable isotopes of carbon and nitrogen confirms isotopic niche partitioning between species despite their physical proximity. Compound-specific nitrogen isotopes of amino acids (δ15N-AA) separated the taxa along continua of trophic position and benthic-pelagic coupling and resolve the conspicuously enriched bulk nitrogen patterns commonly observed in sponges. Radiocarbon dating (as Δ14C) of tissue samples, particulate organic matter (POM) and dissolved inorganic carbon (DIC) from the Scotian Slope sheds light on food provenance and distinguishes diets dominated by older, recalcitrant forms of organic matter versus surface-derived POM. Our results reveal significant differences in resource utilisation among sympatric corals, sponges, ascidians, and anemones and highlight that organisms capable of feeding on more recalcitrant resources will likely play a greater role in supporting deep-water habitats where the quality and flux of fresh POM may be diminished.
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Affiliation(s)
- Wilder Greenman
- Department of Earth and Environmental Sciences, Dalhousie University, Halifax, NS, Canada.
| | | | | | | | - Liam Jasperse
- Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON, Canada
| | - Aislinn Fox
- Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON, Canada
- Department of Earth System Sciences, University of California, Irvine, Irvine, CA, USA
| | - Brett Walker
- Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON, Canada
- Department of Earth System Sciences, University of California, Irvine, Irvine, CA, USA
| | - Evan Edinger
- Department of Geography, Memorial University, St. Johns, Newfoundland, Canada
| | - Owen Sherwood
- Department of Earth and Environmental Sciences, Dalhousie University, Halifax, NS, Canada
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2
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Williams B, Barnes S, Knaak M, Druffel ERM, McCarthy M, Pugsley G, Vokhshoori N, Fiechter J, Etnoyer P, Caldow C. Proteinaceous corals reveal heterogeneity in shifting Southern California oceanographic regimes. MARINE ENVIRONMENTAL RESEARCH 2025; 204:106954. [PMID: 39874872 DOI: 10.1016/j.marenvres.2025.106954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2024] [Revised: 12/20/2024] [Accepted: 01/06/2025] [Indexed: 01/30/2025]
Abstract
The Southern California Bight is an ecologically important region for many local and migratory fauna. We combine bulk and compound-specific amino acid stable isotope measurements in the skeletons of proteinaceous octocorals with new regional ocean modeling system model output to explore biogeochemical changes at two locations within the Bight - Santa Cruz Basin and Santa Barbara Channel. Separated by the Channel Islands, these sites display distinct oceanographic regimes. Corals from the southeastern Santa Cruz Basin display lower bulk δ13C and higher bulk δ15N values than those in the northern Santa Barbara Channel. Amino acid isotope analyses indicate that the higher δ15N values in Santa Cruz Basin reflect both higher δ15N of baseline primary production and nitrate and higher trophic positions of the sinking particles that comprise the coral's diet. These findings suggest low nitrate concentrations, more complete nitrate utilization, lower productivity, and a longer planktonic food web. A 50-year time series of coral skeleton δ15N bulk values increases with time, consistent with sediment cores that capture an increase in the δ15NNO3 advected into the central Bight. In contrast, the Santa Barbara Channel corals display decadal-scale fluctuations, likely driven by interdecadal fluctuations in upwelling and nitrate supply. These findings agree with physical-biogeochemical model simulations showing greater sensitivity of upwelled surface nitrate concentrations to ocean climate variability in the Santa Barbara Channel. The importance of nutrient availability on ecosystem structure is emphasized using compound specific amino acid analysis, in a way that may be overlooked in bulk isotope palaeoceanographic records.
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Affiliation(s)
- Branwen Williams
- Kravis Department of Integrated Sciences, Claremont McKenna College, United States.
| | - Sarah Barnes
- W.M. Keck Science Department, Scripps College, United States
| | - Mary Knaak
- W.M. Keck Science Department, Scripps College, United States
| | - Ellen R M Druffel
- Department of Earth System Science, University of California, Irvine, United States
| | - Matt McCarthy
- Department of Ocean Sciences, University of California, Santa Cruz, United States
| | - Genevieve Pugsley
- Department of Ocean Sciences, University of California, Santa Cruz, United States
| | | | - Jerome Fiechter
- Department of Ocean Sciences, University of California, Santa Cruz, United States
| | - Peter Etnoyer
- NOAA National Centers for Coastal Ocean Science, United States
| | - Chris Caldow
- Channel Islands National Marine Sanctuary, United States
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3
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Terhaar J, Vogt L, Foukal NP. Atlantic overturning inferred from air-sea heat fluxes indicates no decline since the 1960s. Nat Commun 2025; 16:222. [PMID: 39814728 PMCID: PMC11736101 DOI: 10.1038/s41467-024-55297-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2024] [Accepted: 12/06/2024] [Indexed: 01/18/2025] Open
Abstract
The Atlantic Meridional Overturning Circulation (AMOC) is crucial for global ocean carbon and heat uptake, and controls the climate around the North Atlantic. Despite its importance, quantifying the AMOC's past changes and assessing its vulnerability to climate change remains highly uncertain. Understanding past AMOC changes has relied on proxies, most notably sea surface temperature anomalies over the subpolar North Atlantic. Here, we use 24 Earth System Models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to demonstrate that these temperature anomalies cannot robustly reconstruct the AMOC. Instead, we find that air-sea heat flux anomalies north of any given latitude in the North Atlantic between 26.5°N and 50°N are tightly linked to the AMOC anomaly at that latitude on decadal and centennial timescales. On these timescales, air-sea heat flux anomalies are strongly linked to AMOC-driven northward heat flux anomalies through the conservation of energy. On annual timescales, however, air-sea heat flux anomalies are mostly altered by atmospheric variability and less by AMOC anomalies. Based on the here identified relationship and observation-based estimates of the past air-sea heat flux in the North Atlantic from reanalysis products, the decadal averaged AMOC at 26.5°N has not weakened from 1963 to 2017 although substantial variability exists at all latitudes.
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Affiliation(s)
- Jens Terhaar
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
- Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland.
- Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland.
| | - Linus Vogt
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
- Laboratoire d'Océanographie et du Climat Expérimentations et Approches Numériques (LOCEAN), Sorbonne Université, CNRS/IRD/MNHN, Paris, France
| | - Nicholas P Foukal
- Woods Hole Oceanographic Institution, Woods Hole, MA, USA
- Skidaway Institute of Oceanography, University of Georgia, Savannah, GA, USA
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4
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Stewart JA, Williams B, LaVigne M, Wanamaker AD, Strong AL, Jellison B, Whitney NM, Thatcher DL, Robinson LF, Halfar J, Adey W. Delayed onset of ocean acidification in the Gulf of Maine. Sci Rep 2025; 15:2039. [PMID: 39814808 PMCID: PMC11736168 DOI: 10.1038/s41598-024-84537-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2024] [Accepted: 12/24/2024] [Indexed: 01/18/2025] Open
Abstract
The Gulf of Maine holds significant ecological and economic value for fisheries and communities in north-eastern North America. However, there is apprehension regarding its vulnerability to the effects of increasing atmospheric CO2. Substantial recent warming and the inflow of low alkalinity waters into the Gulf of Maine have raised concerns about the impact of ocean acidification on resident marine calcifiers (e.g. oysters, clams, mussels). With limited seawater pH records, the natural variability and drivers of pH in this region remain unclear. To address this, we present coastal water pH proxy records using boron isotope (δ11B) measurements in long-lived, annually banded, crustose coralline algae (1920-2018 CE). These records indicate seawater pH was low (~ 7.9) for much of the last century. Contrary to expectation, we also find that pH has increased (+ 0.2 pH units) over the past 40 years, despite concurrent rising atmospheric CO2. This increase is attributed to an increased input of high alkalinity waters derived from the Gulf Stream. This delayed onset of ocean acidification is cause for concern. Once ocean circulation-driven buffering effects reach their limit, seawater pH decline may occur swiftly. This would profoundly harm shellfisheries and the broader Gulf of Maine ecosystem.
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Affiliation(s)
- Joseph A Stewart
- School of Earth Sci. University of Bristol, Queens Road, Bristol, BS8 1RJ, UK.
| | - Branwen Williams
- Kravis Department of Integrated Science, Claremont McKenna College, 888 Columbia Avenue, Claremont, CA, 91711, USA
| | - Michèle LaVigne
- Department of Earth and Oceanographic Science, Bowdoin College, 6800 College Station, Brunswick, ME, USA
| | - Alan D Wanamaker
- Department of Earth, Atmosphere, and Climate, Iowa State University, 253 Science, 2237 Osborn Drive, Ames, IA, 50010, USA
- National Science Foundation, Alexandria, VA, 22314, USA
| | - Aaron L Strong
- Environmental Studies Program, Hamilton College, 198 College Hill Road, Clinton, NY, 13323, USA
| | - Brittany Jellison
- Department of Earth and Oceanographic Science, Bowdoin College, 6800 College Station, Brunswick, ME, USA
| | - Nina M Whitney
- Marine and Coastal Science, Western Washington University, 516 High Street, Bellingham, WA, 98225, USA
- Physical Oceanography Department, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA, 02543, USA
| | - Diana L Thatcher
- Department of Earth, Atmosphere, and Climate, Iowa State University, 253 Science, 2237 Osborn Drive, Ames, IA, 50010, USA
| | - Laura F Robinson
- School of Earth Sci. University of Bristol, Queens Road, Bristol, BS8 1RJ, UK
- Department of Environment and Geography, University of York, York, UK
| | - Jochen Halfar
- Chemical and Physical Sciences Department, University of Toronto Mississauga, Mississauga, ON, Canada
| | - Walter Adey
- Department of Botany, Smithsonian Institution, National Museum of Natural History, Washington, DC, 20013, USA
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5
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Golikov AV, Xavier JC, Ceia FR, Queirós JP, Bustamante P, Couperus B, Guillou G, Larionova AM, Sabirov RM, Somes CJ, Hoving HJ. Insights on long-term ecosystem changes from stable isotopes in historical squid beaks. BMC Ecol Evol 2024; 24:90. [PMID: 38956464 PMCID: PMC11221165 DOI: 10.1186/s12862-024-02274-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Accepted: 06/17/2024] [Indexed: 07/04/2024] Open
Abstract
BACKGROUND Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023. RESULTS We detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii's trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century. CONCLUSIONS Our results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids' increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.
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Affiliation(s)
| | - José C Xavier
- MARE-Marine and Environmental Sciences Centre/ARNET-Aquatic Research Network, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- British Antarctic Survey, Natural Environment Research Council, Cambridge, UK
| | - Filipe R Ceia
- MARE-Marine and Environmental Sciences Centre/ARNET-Aquatic Research Network, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - José P Queirós
- MARE-Marine and Environmental Sciences Centre/ARNET-Aquatic Research Network, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- British Antarctic Survey, Natural Environment Research Council, Cambridge, UK
| | - Paco Bustamante
- Littoral Environnement et Sociétés (LIENSs), UMR 7266, CNRS-La Rochelle Université, La Rochelle, France
| | - Bram Couperus
- Wageningen Marine Research, Wageningen University and Research, IJmuiden, The Netherlands
| | - Gaël Guillou
- Littoral Environnement et Sociétés (LIENSs), UMR 7266, CNRS-La Rochelle Université, La Rochelle, France
| | | | | | | | - Henk-Jan Hoving
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
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6
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Sackett DK, Chrisp JK, Farmer TM. Isotopes and otolith chemistry provide insight into the biogeochemical history of mercury in southern flounder across a salinity gradient. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2024; 26:233-246. [PMID: 38284178 DOI: 10.1039/d3em00482a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2024]
Abstract
Methylmercury (MeHg) continues to pose a significant global health risk to wildlife and humans through fish consumption. Despite numerous advancements in understanding the mercury (Hg) cycle, questions remain about MeHg sources that accumulate in fish, particularly across transitional coastal areas, where harvest is prominent and Hg sources are numerous. Here we used a unique combination of Hg and nutrient isotopes, and otolith chemistry to trace the biogeochemical history of Hg and identify Hg sources that accumulated in an economically important fish species across Mobile Bay, Alabama (USA). Fish tissue Hg in our samples primarily originated from wet deposition within the watershed, and partly reflected legacy industrial Hg. Results also suggest that little Hg was lost through photochemical processes (<10% of fish tissue Hg underwent photochemical processes). Of the small amount that did occur, photodegradation of the organic form, MeHg, was not the dominant process. Biotic transformation processes were estimated to have been a primary driver of Hg fractionation (∼93%), with isotope results indicating methylation as the primary biotic fractionation process prior to Hg entering the foodweb. On a finer scale, individual lifetime estuarine habitat use influenced Hg sources that accumulated in fish and fish Hg concentrations, with runoff from terrestrial Hg sources having a larger influence on fish in freshwater regions of the estuary compared to estuarine regions. Overall, results suggest increases in Hg inputs to the Mobile Bay watershed from wet deposition, turnover of legacy sources, and runoff are likely to translate into increased uptake into the foodweb.
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Affiliation(s)
- Dana K Sackett
- Department of Environmental Science and Technology, University of Maryland, 8127 Regents Dr, College Park, MD 20742, USA.
| | - Jared K Chrisp
- Department of Forestry and Environmental Conservation, Clemson University, 262 Lehotsky Hall, Clemson, SC 29634, USA
| | - Troy M Farmer
- Department of Forestry and Environmental Conservation, Clemson University, 262 Lehotsky Hall, Clemson, SC 29634, USA
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7
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Steinkopf M, Krumme U, Schulz‐Bull D, Wodarg D, Loick‐Wilde N. Trophic lengthening triggered by filamentous, N 2-fixing cyanobacteria disrupts pelagic but not benthic food webs in a large estuarine ecosystem. Ecol Evol 2024; 14:e11048. [PMID: 38380063 PMCID: PMC10877452 DOI: 10.1002/ece3.11048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 01/19/2024] [Accepted: 02/05/2024] [Indexed: 02/22/2024] Open
Abstract
Eutrophication, increased temperatures and stratification can lead to massive, filamentous, N2-fixing cyanobacterial (FNC) blooms in coastal ecosystems with largely unresolved consequences for the mass and energy supply in food webs. Mesozooplankton adapt to not top-down controlled FNC blooms by switching diets from phytoplankton to microzooplankton, resulting in a directly quantifiable increase in its trophic position (TP) from 2.0 to as high as 3.0. If this process in mesozooplankton, we call trophic lengthening, was transferred to higher trophic levels of a food web, a loss of energy could result in massive declines of fish biomass. We used compound-specific nitrogen stable isotope data of amino acids (CSIA) to estimate and compare the nitrogen (N) sources and TPs of cod and flounder from FNC bloom influence areas (central Baltic Sea) and areas without it (western Baltic Sea). We tested if FNC-triggered trophic lengthening in mesozooplankton is carried over to fish. The TP of cod from the western Baltic (4.1 ± 0.5), feeding mainly on decapods, was equal to reference values. Only cod from the central Baltic, mainly feeding on zooplanktivorous pelagics, had a significantly higher TP (4.6 ± 0.4), indicating a strong carry-over effect trophic lengthening from mesozooplankton. In contrast, the TP of molluscivorous flounder, associated with the benthic food web, was unaffected by trophic lengthening and quite similar reference values of 3.2 ± 0.2 in both areas. This suggests that FNC blooms lead to a large loss of energy in zooplanktivorous but not in molluscivorous mesopredators. If FNC blooms continue to trigger the detour of energy at the base of the pelagic food web due to a massive heterotrophic microbial system, the TP of cod will not return to lower TP values and the fish stock not recover. Monitoring the TP of key species can identify fundamental changes in ecosystems and provide information for resource management.
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Affiliation(s)
- Markus Steinkopf
- Department of Biological OceanographyLeibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Uwe Krumme
- Thünen Institute of Baltic Sea FisheriesRostockGermany
| | - Detlef Schulz‐Bull
- Department of Marine ChemistryLeibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Dirk Wodarg
- Department of Marine ChemistryLeibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Natalie Loick‐Wilde
- Department of Biological OceanographyLeibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
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8
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Robinson RS, Smart SM, Cybulski JD, McMahon KW, Marcks B, Nowakowski C. Insights from Fossil-Bound Nitrogen Isotopes in Diatoms, Foraminifera, and Corals. ANNUAL REVIEW OF MARINE SCIENCE 2023; 15:407-430. [PMID: 35977410 DOI: 10.1146/annurev-marine-032122-104001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Nitrogen is a major limiting element for biological productivity, and thus understanding past variations in nitrogen cycling is central to understanding past and future ocean biogeochemical cycling, global climate cycles, and biodiversity. Organic nitrogen encapsulated in fossil biominerals is generally protected from alteration, making it an important archive of the marine nitrogen cycle on seasonal to million-year timescales. The isotopic composition of fossil-bound nitrogen reflects variations in the large-scale nitrogen inventory, local sources and processing, and ecological and physiological traits of organisms. The ability to measure trace amounts of fossil-bound nitrogen has expanded with recent method developments. In this article, we review the foundations and ground truthing for three important fossil-bound proxy types: diatoms, foraminifera, and corals. We highlight their utility with examples of high-resolution evidence for anthropogenic inputs of nitrogen to the oceans, glacial-interglacial-scale assessments of nitrogen inventory change, and evidence for enhanced CO2 drawdown in the high-latitude ocean. Future directions include expanded method development, characterization of ecological and physiological variation, and exploration of extended timescales to push reconstructions further back in Earth's history.
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Affiliation(s)
- Rebecca S Robinson
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; , , , ,
| | - Sandi M Smart
- Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama, USA;
| | - Jonathan D Cybulski
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; , , , ,
- Smithsonian Tropical Research Institute, Balboa, Republic of Panama
| | - Kelton W McMahon
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; , , , ,
| | - Basia Marcks
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; , , , ,
| | - Catherine Nowakowski
- Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA; , , , ,
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9
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OHKOUCHI N. A new era of isotope ecology: Nitrogen isotope ratio of amino acids as an approach for unraveling modern and ancient food web. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2023; 99:131-154. [PMID: 37164681 PMCID: PMC10225296 DOI: 10.2183/pjab.99.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 04/03/2023] [Indexed: 05/12/2023]
Abstract
Food web research is rapidly expanding through study of natural fractional abundance of 15N in individual amino acids. This paper overviews the principles of this isotope approach, and from my perspective, reanalyzes applications, and further extends the discussion. It applies kinetic isotope effects that enriches 15N in certain amino acids associated with the metabolic processes, which was clearly demonstrated by observations of both natural ecosystem and laboratory experiments. In trophic processes 'trophic amino acids' such as glutamic acid that significantly enrich 15N, whereas 'source amino acids' such as phenylalanine and methionine show little 15N enrichment. Through various applications conducted over the years, the principles of the method have shown to operate well and disentangle complex food webs and relevant problems. Applications include food chain length estimate, nitrogen resource assessment, tracking fish migration, and reconstruction of paleodiet. With this approach, considerations of a wide range of classical issues have been reinvigorated, while in the same time, new challenging frontiers are emerging.
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Affiliation(s)
- Naohiko OHKOUCHI
- Biogeochemistry Research Center, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa, Japan
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10
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Yun HY, Larsen T, Choi B, Won E, Shin K. Amino acid nitrogen and carbon isotope data: Potential and implications for ecological studies. Ecol Evol 2022; 12:e8929. [PMID: 35784034 PMCID: PMC9163675 DOI: 10.1002/ece3.8929] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 04/18/2022] [Accepted: 04/25/2022] [Indexed: 12/17/2022] Open
Abstract
Explaining food web dynamics, stability, and functioning depend substantially on understanding of feeding relations within a community. Bulk stable isotope ratios (SIRs) in natural abundance are well-established tools to express direct and indirect feeding relations as continuous variables across time and space. Along with bulk SIRs, the SIRs of individual amino acids (AAs) are now emerging as a promising and complementary method to characterize the flow and transformation of resources across a diversity of organisms, from microbial domains to macroscopic consumers. This significant AA-SIR capacity is based on empirical evidence that a consumer's SIR, specific to an individual AA, reflects its diet SIR coupled with a certain degree of isotopic differences between the consumer and its diet. However, many empirical ecologists are still unfamiliar with the scope of applicability and the interpretative power of AA-SIR. To fill these knowledge gaps, we here describe a comprehensive approach to both carbon and nitrogen AA-SIR assessment focusing on two key topics: pattern in AA-isotope composition across spatial and temporal scales, and a certain variability of AA-specific isotope differences between the diet and the consumer. On this basis we review the versatile applicability of AA-SIR to improve our understanding of physiological processes as well as food web functioning, allowing us to reconstruct dominant basal dietary sources and trace their trophic transfers at the specimen and community levels. Given the insightful and opportunities of AA-SIR, we suggest future applications for the dual use of carbon and nitrogen AA-SIR to study more realistic food web structures and robust consumer niches, which are often very difficult to explain in nature.
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Affiliation(s)
- Hee Young Yun
- Deparment of Marine Science and Convergent TechnologyHanyang UniversityAnsanKorea
| | - Thomas Larsen
- Department of ArchaeologyMax Planck Institute for the Science of Human HistoryJenaGermany
| | - Bohyung Choi
- Deparment of Marine Science and Convergent TechnologyHanyang UniversityAnsanKorea
- Inland Fisheries Research InstituteNational Institute of Fisheries ScienceGeumsan‐gunKorea
| | - Eun‐Ji Won
- Deparment of Marine Science and Convergent TechnologyHanyang UniversityAnsanKorea
| | - Kyung‐Hoon Shin
- Deparment of Marine Science and Convergent TechnologyHanyang UniversityAnsanKorea
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11
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Four millennia of long-term individual foraging site fidelity in a highly migratory marine predator. Commun Biol 2022; 5:368. [PMID: 35422088 PMCID: PMC9010445 DOI: 10.1038/s42003-022-03310-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 03/22/2022] [Indexed: 11/08/2022] Open
Abstract
AbstractTheory and field studies suggest that long-term individual foraging site fidelity (IFSF) may be an important adaptation to competition from increasing population. However, the driving mechanisms and extent of long-term IFSF in wild populations of long-lived, migratory animals has been logistically difficult to study, with only a few confirmed instances. Temporal isotopic datasets can reveal long-term patterns in geographical foraging behaviour. We investigate the isotopic compositions of endangered short-tailed albatross (Phoebastria albatrus) over four millennia leading up to their near-extinction. Although not exhibited by short-tailed albatross today, we show past sub-populations displayed a high-degree of long-term IFSF, focusing on the same locations for hundreds of generations. This is the first large-scale evidence for the deep antiquity of long-term IFSF and suggests that it’s density-driven. Globally, as populations of species like short-tailed albatross continue to recover from overexploitation, potential for resurgence of geographic specialization may increase exposure to localized hazards, requiring closer conservation monitoring.
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12
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Zhang L, Lee WMC, Kreider-Mueller A, Kuhnel E, Baca J, Ji C, Altabet M. High-precision measurement of phenylalanine and glutamic acid δ 15 N by coupling ion-exchange chromatography and purge-and-trap continuous-flow isotope ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2021; 35:e9085. [PMID: 33733521 DOI: 10.1002/rcm.9085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Revised: 03/12/2021] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
RATIONALE Nitrogen isotopic compositions (δ15 N) of source and trophic amino acids (AAs) are crucial tracers of N sources and trophic enrichments in diverse fields, including archeology, astrobiochemistry, ecology, oceanography, and paleo-sciences. The current analytical technique using gas chromatography-combustion-isotope ratio mass spectrometry (GC/C/IRMS) requires derivatization, which is not compatible with some key AAs. Another approach using high-performance liquid chromatography-elemental analyzer-IRMS (HPLC/EA/IRMS) may experience coelution issues with other compounds in certain types of samples, and the highly sensitive nano-EA/IRMS instrumentations are not widely available. METHODS We present a method for high-precision δ15 N measurements of AAs (δ15 N-AA) optimized for canonical source AA-phenylalanine (Phe) and trophic AA-glutamic acid (Glu). This offline approach entails purification and separation via high-pressure ion-exchange chromatography (IC) with automated fraction collection, the sequential chemical conversion of AA to nitrite and then to nitrous oxide (N2 O), and the final determination of δ15 N of the produced N2 O via purge-and-trap continuous-flow isotope ratio mass spectrometry (PT/CF/IRMS). RESULTS The cross-plots of δ15 N of Glu and Phe standards (four different natural-abundance levels) generated by this method and their accepted values have a linear regression slope of 1 and small intercepts demonstrating high accuracy. The precisions were 0.36‰-0.67‰ for Phe standards and 0.27‰-0.35‰ for Glu standards. Our method and the GC/C/IRMS approach produced equivalent δ15 N values for two lab standards (McCarthy Lab AA mixture and cyanobacteria) within error. We further tested our method on a wide range of natural sample matrices and obtained reasonable results. CONCLUSIONS Our method provides a reliable alternative to the current methods for δ15 N-AA measurement as IC or HPLC-based techniques that can collect underivatized AAs are widely available. Our chemical approach that converts AA to N2 O can be easily implemented in laboratories currently analyzing δ15 N of N2 O using PT/CF/IRMS. This method will help promote the use of δ15 N-AA in important studies of N cycling and trophic ecology in a wide range of research areas.
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Affiliation(s)
- Lin Zhang
- Texas A&M University Corpus Christi, Corpus Christi, Texas, USA
| | | | - Ava Kreider-Mueller
- School for Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, Massachusetts, USA
| | - Evelyn Kuhnel
- Texas A&M University Corpus Christi, Corpus Christi, Texas, USA
| | - Jesus Baca
- Texas A&M University Corpus Christi, Corpus Christi, Texas, USA
| | - Chongxiao Ji
- Texas A&M University Corpus Christi, Corpus Christi, Texas, USA
| | - Mark Altabet
- School for Marine Science and Technology, University of Massachusetts Dartmouth, New Bedford, Massachusetts, USA
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13
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Feddern ML, Holtgrieve GW, Ward EJ. Stable isotope signatures in historic harbor seal bone link food web-assimilated carbon and nitrogen resources to a century of environmental change. GLOBAL CHANGE BIOLOGY 2021; 27:2328-2342. [PMID: 33749968 DOI: 10.1111/gcb.15551] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
Anthropogenic climate change will impact nutrient cycles, primary production, and ecosystem structure in the world's oceans, although considerable uncertainty exists regarding the magnitude and spatial variability of these changes. Understanding how regional-scale ocean conditions control nutrient availability and ultimately nutrient assimilation into food webs will inform how marine resources will change in response to climate. To evaluate how ocean conditions influence the assimilation of nitrogen and carbon into coastal marine food webs, we applied a novel dimension reduction analysis to a century of newly acquired molecular isotope data derived from historic harbor seal bone specimens. By measuring bulk δ13 C and δ15 N values of source amino acids of these top predators from 1928 to 2014, we derive indices of primary production and nitrogen resources that are assimilated into food webs. We determined coastal food webs responded to climate regimes, coastal upwelling, and freshwater discharge, yet the strength of responses to individual drivers varied across the northeast Pacific. Indices of primary production and nitrogen availability in the Gulf of Alaska were dependent on regional climate indices (i.e., North Pacific Gyre Oscillation) and upwelling. In contrast, the coastal Washington and Salish Sea food webs were associated with local indices of freshwater discharge. For some regions (eastern Bering Sea, northern Gulf of Alaska) food web-assimilated production was coupled with nitrogen sources; however, other regions demonstrated no production-nitrogen coupling (Salish Sea). Temporal patterns of environmental indices and isotopic data from Washington state varied about the long-term mean with no directional trend. Data from the Gulf of Alaska, however, showed below average harbor seal δ13 C values and above average ocean conditions since 1975, indicating a change in primary production in recent decades. Altogether, these findings demonstrate stable isotope data can provide useful indices of nitrogen resources and phytoplankton dynamics specific to what is assimilated by food webs.
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Affiliation(s)
- Megan L Feddern
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
| | - Gordon W Holtgrieve
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
| | - Eric J Ward
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, Seattle, WA, USA
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14
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Matthews CJD, Ruiz-Cooley RI, Pomerleau C, Ferguson SH. Amino acid δ 15N underestimation of cetacean trophic positions highlights limited understanding of isotopic fractionation in higher marine consumers. Ecol Evol 2020; 10:3450-3462. [PMID: 32274001 PMCID: PMC7141024 DOI: 10.1002/ece3.6142] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 01/31/2020] [Accepted: 02/05/2020] [Indexed: 01/23/2023] Open
Abstract
Compound-specific stable isotope analysis (CSIA) of amino acids (AAs) has been rapidly incorporated in ecological studies to resolve consumer trophic position (TP). Differential 15N fractionation of "trophic" AAs, which undergo trophic 15N enrichment, and "source" AAs, which undergo minimal trophic 15N enrichment and serve as a proxy for primary producer δ15N values, allows for internal calibration of TP. Recent studies, however, have shown the difference between source and trophic AA δ15N values in higher marine consumers is less than predicted from empirical studies of invertebrates and fish. To evaluate CSIA-AA for estimating TP of cetaceans, we compared source and trophic AA δ15N values of multiple tissues (skin, baleen, and dentine collagen) from five species representing a range of TPs: bowhead whales, beluga whales, short-beaked common dolphins, sperm whales, and fish-eating (FE) and marine mammal-eating (MME) killer whale ecotypes. TP estimates (TPCSIA) using several empirically derived equations and trophic discrimination factors (TDFs) were 1-2.5 trophic steps lower than stomach content-derived estimates (TPSC) for all species. Although TPCSIA estimates using dual TDF equations were in better agreement with TPSC estimates, our data do not support the application of universal or currently available dual TDFs to estimate cetacean TPs. Discrepancies were not simply due to inaccurate TDFs, however, because the difference between consumer glutamic acid/glutamine (Glx) and phenylalanine (Phe) δ15N values (δ15NGlx-Phe) did not follow expected TP order. In contrast to pioneering studies on invertebrates and fish, our data suggest trophic 15N enrichment of Phe is not negligible and should be examined among the potential mechanisms driving "compressed" and variable δ15NGlx-Phe values at high TPs. We emphasize the need for controlled diet studies to understand mechanisms driving AA-specific isotopic fractionation before widespread application of CSIA-AA in ecological studies of cetaceans and other marine consumers.
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Affiliation(s)
- Cory J D Matthews
- Arctic Aquatic Research Division Fisheries and Oceans Canada Winnipeg MB Canada
| | - Rocio I Ruiz-Cooley
- Departamento de Oceanografía Biológica Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) Ensenada México
- Moss Landing Marine Laboratories California State University Moss Landing CA USA
| | - Corinne Pomerleau
- Institut Maurice Lamontagne, Fisheries and Oceans Canada Mont-Joli QC Canada
| | - Steven H Ferguson
- Arctic Aquatic Research Division Fisheries and Oceans Canada Winnipeg MB Canada
- Department of Biological Sciences University of Manitoba Winnipeg MB Canada
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15
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Tan K, Zheng H. Ocean acidification and adaptive bivalve farming. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 701:134794. [PMID: 31715479 DOI: 10.1016/j.scitotenv.2019.134794] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/30/2019] [Accepted: 10/01/2019] [Indexed: 06/10/2023]
Abstract
Multiple lines of evidence, ranging from time series field observations to climate change stimulation experiments demonstrate the negative effects of global warming and ocean acidification (OA) on bivalve molluscs. The impact of global warming on bivalve aquaculture has recently been reviewed. However, the impact of OA on bivalve aquaculture has received relatively less attention. Although there are many reports on the effects of OA on bivalves, this information is poorly organized and the connection between OA and bivalve aquaculture is unclear. Therefore, understanding the potential impact of acidification on ecosystems and bivalve aquaculture is of prime importance. Here, we provide a comprehensive scientific review of the impact of OA on bivalves and propose mitigation measures for future bivalve farming. This information will help to establish aquaculture and fisheries management plans to be implemented in commercial fisheries and nature conservation. In general, scientific evidence suggests that OA threatens bivalves by diminishing the availability of carbonate minerals, which may adversely affect the development of early life stages, calcification, growth, byssus attachment and survival of bivalves. The Integrated multi-trophic aquaculture (IMTA) approach is a useful method in slowing the effects of climate change, thereby providing longer adaptation period for bivalves to changing ocean conditions. However, for certain regions that experience intense OA effects or for certain bivalve species that have much longer generational time, IMTA alone may not be sufficient to protect bivalves from the adverse effects of climate change. Therefore, it is highly recommended to combine IMTA and genetic breeding methods to facilitate transgenerational acclimation or evolution processes to enhance the climate resilience of bivalves.
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Affiliation(s)
- Karsoon Tan
- Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou 515063, China; Mariculture Research Center for Subtropical Shellfish & Algae of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China
| | - Huaiping Zheng
- Key Laboratory of Marine Biotechnology of Guangdong Province, Shantou University, Shantou 515063, China; Mariculture Research Center for Subtropical Shellfish & Algae of Guangdong Province, Shantou 515063, China; STU-UMT Joint Shellfish Research Laboratory, Shantou University, Shantou 515063, China.
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16
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Hetherington ED, Kurle CM, Ohman MD, Popp BN. Effects of chemical preservation on bulk and amino acid isotope ratios of zooplankton, fish, and squid tissues. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2019; 33:935-945. [PMID: 30730594 DOI: 10.1002/rcm.8408] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 12/31/2018] [Accepted: 01/31/2019] [Indexed: 06/09/2023]
Abstract
RATIONALE It is imperative to understand how chemical preservation alters tissue isotopic compositions before using historical samples in ecological studies. Specifically, although compound-specific isotope analysis of amino acids (CSIA-AA) is becoming a widely used tool, there is little information on how preservation techniques affect amino acid δ15 N values. METHODS We evaluated the effects of chemical preservatives on bulk tissue δ13 C and δ15 N and amino acid δ15 N values, measured by gas chromatography/isotope ratio mass spectrometry (GC/IRMS), of (a) tuna (Thunnus albacares) and squid (Dosidicus gigas) muscle tissues that were fixed in formaldehyde and stored in ethanol for 2 years and (b) two copepod species, Calanus pacificus and Eucalanus californicus, which were preserved in formaldehyde for 24-25 years. RESULTS Tissues in formaldehyde-ethanol had higher bulk δ15 N values (+1.4, D. gigas; +1.6‰, T. albacares), higher δ13 C values for D. gigas (+0.5‰), and lower δ13 C values for T. albacares (-0.8‰) than frozen samples. The bulk δ15 N values from copepods were not different those from frozen samples, although the δ13 C values from both species were lower (-1.0‰ for E. californicus and -2.2‰ for C. pacificus) than those from frozen samples. The mean amino acid δ15 N values from chemically preserved tissues were largely within 1‰ of those of frozen tissues, but the phenylalanine δ15 N values were altered to a larger extent (range: 0.5-4.5‰). CONCLUSIONS The effects of preservation on bulk δ13 C values were variable, where the direction and magnitude of change varied among taxa. The changes in bulk δ15 N values associated with chemical preservation were mostly minimal, suggesting that storage in formaldehyde or ethanol will not affect the interpretation of δ15 N values used in ecological studies. The preservation effects on amino acid δ15 N values were also mostly minimal, mirroring bulk δ15 N trends, which is promising for future CSIA-AA studies of archived specimens. However, there were substantial differences in phenylalanine and valine δ15 N values, which we speculate resulted from interference in the chromatographic resolution of unknown compounds rather than alteration of tissue isotopic composition due to chemical preservation.
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Affiliation(s)
- Elizabeth D Hetherington
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Carolyn M Kurle
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Mark D Ohman
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | - Brian N Popp
- Department of Earth Sciences, University of Hawaii at Manoa, Honolulu, HI, USA
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17
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Loick‐Wilde N, Fernández‐Urruzola I, Eglite E, Liskow I, Nausch M, Schulz‐Bull D, Wodarg D, Wasmund N, Mohrholz V. Stratification, nitrogen fixation, and cyanobacterial bloom stage regulate the planktonic food web structure. GLOBAL CHANGE BIOLOGY 2019; 25:794-810. [PMID: 30628151 PMCID: PMC6850720 DOI: 10.1111/gcb.14546] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 09/28/2018] [Accepted: 11/07/2018] [Indexed: 05/19/2023]
Abstract
Changes in the complexity of planktonic food webs may be expected in future aquatic systems due to increases in sea surface temperature and an enhanced stratification of the water column. Under these conditions, the growth of unpalatable, filamentous, N2 -fixing cyanobacterial blooms, and their effect on planktonic food webs will become increasingly important. The planktonic food web structure in aquatic ecosystems at times of filamentous cyanobacterial blooms is currently unresolved, with discordant lines of evidence suggesting that herbivores dominate the mesozooplankton or that mesozooplankton organisms are mainly carnivorous. Here, we use a set of proxies derived from amino acid nitrogen stable isotopes from two mesozooplankton size fractions to identify changes in the nitrogen source and the planktonic food web structure across different microplankton communities. A transition from herbivory to carnivory in mesozooplankton between more eutrophic, near-coastal sites and more oligotrophic, offshore sites was accompanied by an increasing diversity of microplankton communities with aging filamentous cyanobacterial blooms. Our analyses of 124 biotic and abiotic variables using multivariate statistics confirmed salinity as a major driver for the biomass distribution of non-N2 -fixing microplankton species such as dinoflagellates. However, we provide strong evidence that stratification, N2 fixation, and the stage of the cyanobacterial blooms regulated much of the microplankton diversity and the mean trophic position and size of the metabolic nitrogen pool in mesozooplankton. Our empirical, macroscale data set consistently unifies contrasting results of the dominant feeding mode in mesozooplankton during blooms of unpalatable, filamentous, N2 -fixing cyanobacteria by identifying the at times important role of heterotrophic microbial food webs. Thus, carnivory, rather than herbivory, dominates in mesozooplankton during aging and decaying cyanobacterial blooms with hitherto uncharacterized consequences for the biogeochemical functions of mesozooplankton.
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Affiliation(s)
| | - Igor Fernández‐Urruzola
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
- Present address:
Millennium Institute of Oceanography (IMO)University of ConcepcionConcepciónChile
| | - Elvita Eglite
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Iris Liskow
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Monika Nausch
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | | | - Dirk Wodarg
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Norbert Wasmund
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
| | - Volker Mohrholz
- Leibniz Institute for Baltic Sea Research WarnemuendeRostockGermany
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18
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Claret M, Galbraith ED, Palter JB, Bianchi D, Fennel K, Gilbert D, Dunne JP. Rapid coastal deoxygenation due to ocean circulation shift in the NW Atlantic. NATURE CLIMATE CHANGE 2018; 8:866-872. [PMID: 30416585 PMCID: PMC6218011 DOI: 10.1038/s41558-018-0263-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 07/27/2018] [Indexed: 05/23/2023]
Abstract
Global observations show that the ocean lost approximately 2% of its oxygen inventory over the last five decades 1-3, with important implications for marine ecosystems 4, 5. The rate of change varies with northwest Atlantic coastal waters showing a long-term drop 6, 7 that vastly outpaces the global and North Atlantic basin mean deoxygenation rates 5, 8. However, past work has been unable to resolve mechanisms of large-scale climate forcing from local processes. Here, we use hydrographic evidence to show a Labrador Current retreat is playing a key role in the deoxygenation on the northwest Atlantic shelf. A high-resolution global coupled climate-biogeochemistry model 9 reproduces the observed decline of saturation oxygen concentrations in the region, driven by a retreat of the equatorward-flowing Labrador Current and an associated shift toward more oxygen-poor subtropical waters on the shelf. The dynamical changes underlying the shift in shelf water properties are correlated with a slowdown in the simulated Atlantic Meridional Overturning Circulation 10. Our results provide strong evidence that a major, centennial-scale change of the Labrador Current is underway, and highlight the potential for ocean dynamics to impact coastal deoxygenation over the coming century.
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Affiliation(s)
- Mariona Claret
- Joint Institute for the Study of the Atmosphere and the Ocean, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
- Department of Earth and Planetary Sciences, McGill University, Montréal, QC, Canada
| | - Eric D Galbraith
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
- Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain
- Department of Earth and Planetary Sciences, McGill University, Montréal, QC, Canada
| | - Jaime B Palter
- Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA
| | - Daniele Bianchi
- Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
| | - Katja Fennel
- Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Denis Gilbert
- Maurice Lamontagne Institute, Fisheries and Oceans Canada, Mont-Joli, QC, Canada
| | - John P Dunne
- NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA
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19
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Natural forcing of the North Atlantic nitrogen cycle in the Anthropocene. Proc Natl Acad Sci U S A 2018; 115:10606-10611. [PMID: 30275314 DOI: 10.1073/pnas.1801049115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human alteration of the global nitrogen cycle intensified over the 1900s. Model simulations suggest that large swaths of the open ocean, including the North Atlantic and the western Pacific, have already been affected by anthropogenic nitrogen through atmospheric transport and deposition. Here we report an ∼130-year-long record of the 15N/14N of skeleton-bound organic matter in a coral from the outer reef of Bermuda, which provides a test of the hypothesis that anthropogenic atmospheric nitrogen has significantly augmented the nitrogen supply to the open North Atlantic surface ocean. The Bermuda 15N/14N record does not show a long-term decline in the Anthropocene of the amplitude predicted by model simulations or observed in a western Pacific coral 15N/14N record. Rather, the decadal variations in the Bermuda 15N/14N record appear to be driven by the North Atlantic Oscillation, most likely through changes in the formation rate of Subtropical Mode Water. Given that anthropogenic nitrogen emissions have been decreasing in North America since the 1990s, this study suggests that in the coming decades, the open North Atlantic will remain minimally affected by anthropogenic nitrogen deposition.
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20
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Observed fingerprint of a weakening Atlantic Ocean overturning circulation. Nature 2018; 556:191-196. [DOI: 10.1038/s41586-018-0006-5] [Citation(s) in RCA: 430] [Impact Index Per Article: 61.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 02/23/2018] [Indexed: 11/08/2022]
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21
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Sackett DK, Drazen JC, Popp BN, Choy CA, Blum JD, Johnson MW. Carbon, Nitrogen, and Mercury Isotope Evidence for the Biogeochemical History of Mercury in Hawaiian Marine Bottomfish. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:13976-13984. [PMID: 29132209 DOI: 10.1021/acs.est.7b04893] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The complex biogeochemical cycle of Hg makes identifying primary sources of fish tissue Hg problematic. To identify sources and provide insight into this cycle, we combined carbon (δ13C), nitrogen amino acid (δ15NPhe), and Hg isotope (Δ199Hg, Δ201Hg, δ202Hg) data for six species of Hawaiian marine bottomfish. Results from these isotopic systems identified individuals within species that likely fed from separate food webs. Terrestrial freshwater inputs to coastal sediments were identified as the primary source of tissue Hg in the jack species, Caranx ignobilis, which inhabit shallow marine ecosystems. Thus, coastal C. ignobilis were a biological vector transporting Hg from freshwater environments into marine ecosystems. Depth profiles of Hg isotopic compositions for bottomfish (excludung C. ignobilis) were similar, but not identical, to profiles for open-ocean pelagic fishes, suggesting that in both settings inorganic Hg, which was ultimately transformed to monomethylmercury (MeHg) and bioaccumulated, was dominantly from a single source. However, differences between pelagic fish and bottomfish profiles were attributable to mass-dependent fractionation in the benthos prior to incorporation into the food web. Results also confirmed that bottomfish relied, at least in part, on a benthic food web and identified the incorporation of deeper water oceanic MeHg sources into deeper water sediments prior to food web uptake and transfer.
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Affiliation(s)
- Dana K Sackett
- School of Fisheries, Aquaculture, and Aquatic Sciences, Auburn University , Auburn, Alabama 36849, United States
| | - Jeffrey C Drazen
- Department of Oceanography, University of Hawaii , Manoa, 1000 Pope Road, Honolulu, Hawaii 96822, United States
| | - Brian N Popp
- Department of Geology and Geophysics, University of Hawaii , Manoa, 1680 East-West Road, Honolulu, Hawaii 96822, United States
| | - C Anela Choy
- Monterey Bay Aquarium Research Institute , 7700 Sandholdt Road, Moss Landing, California 95039, United States
| | - Joel D Blum
- Department of Earth and Environmental Sciences, University of Michigan , 1100 N University Avenue, Ann Arbor, Michigan 48109, United States
| | - Marcus W Johnson
- Department of Earth and Environmental Sciences, University of Michigan , 1100 N University Avenue, Ann Arbor, Michigan 48109, United States
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22
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Ruiz-Cooley RI, Gerrodette T, Fiedler PC, Chivers SJ, Danil K, Ballance LT. Temporal variation in pelagic food chain length in response to environmental change. SCIENCE ADVANCES 2017; 3:e1701140. [PMID: 29057322 PMCID: PMC5647130 DOI: 10.1126/sciadv.1701140] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 09/20/2017] [Indexed: 05/31/2023]
Abstract
Climate variability alters nitrogen cycling, primary productivity, and dissolved oxygen concentration in marine ecosystems. We examined the role of this variability (as measured by six variables) on food chain length (FCL) in the California Current (CC) by reconstructing a time series of amino acid-specific δ15N values derived from common dolphins, an apex pelagic predator, and using two FCL proxies. Strong declines in FCL were observed after the 1997-1999 El Niño Southern Oscillation (ENSO) event. Bayesian models revealed longer FCLs under intermediate conditions for surface temperature, chlorophyll concentration, multivariate ENSO index, and total plankton volume but not for hypoxic depth and nitrate concentration. Our results challenge the prevalent paradigm that suggested long-term stability in the food web structure in the CC and, instead, reveal that pelagic food webs respond strongly to disturbances associated with ENSO events, local oceanography, and ongoing changes in climate.
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Affiliation(s)
- Rocio I. Ruiz-Cooley
- Moss Landing Marine Laboratories, San Jose State University, Moss Landing, CA 95039, USA
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
| | - Tim Gerrodette
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
| | - Paul C. Fiedler
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
| | - Susan J. Chivers
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
| | - Kerri Danil
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
| | - Lisa T. Ballance
- Southwest Fisheries Science Center, National Oceanic and Atmospheric Administration Fisheries Service, La Jolla, CA 92037, USA
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA
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23
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Hückstädt LA, McCarthy MD, Koch PL, Costa DP. What difference does a century make? Shifts in the ecosystem structure of the Ross Sea, Antarctica, as evidenced from a sentinel species, the Weddell seal. Proc Biol Sci 2017; 284:20170927. [PMID: 28855359 PMCID: PMC5577480 DOI: 10.1098/rspb.2017.0927] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 07/24/2017] [Indexed: 01/29/2023] Open
Abstract
The arrival of humans to Antarctica's Ross Sea (100+ years ago) led to a slow, but sustained increase in human activities in the area. To investigate if human presence has influenced the structure of the ecosystem over the last century, we compared historical (ca 100 years old) and modern samples of a sentinel species, the Weddell seal (Leptonychotes weddellii), using both bulk tissue and compound-specific stable isotope analysis. The historical isotopic niche of Weddell seals was over five times larger than the modern niche. The isotopic values of individual amino acids showed a clear segregation between historical and modern samples, indicative of differences at the base of the trophic web. Further, we found no significant differences in the trophic position of Weddell seals between the two periods. Our study revealed that the Ross Sea has undergone detectable changes (i.e. in the primary producers community) in the last century, but the presence of humans has not disrupted trophic interactions supporting Weddell seals.
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Affiliation(s)
- Luis A Hückstädt
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Matthew D McCarthy
- Department of Ocean Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Paul L Koch
- Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
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Reconstructing variability in West Greenland ocean biogeochemistry and bowhead whale (Balaena mysticetus) food web structure using amino acid isotope ratios. Polar Biol 2017. [DOI: 10.1007/s00300-017-2136-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Takizawa Y, Dharampal PS, Steffan SA, Takano Y, Ohkouchi N, Chikaraishi Y. Intra-trophic isotopic discrimination of 15N/ 14N for amino acids in autotrophs: Implications for nitrogen dynamics in ecological studies. Ecol Evol 2017; 7:2916-2924. [PMID: 28479991 PMCID: PMC5415530 DOI: 10.1002/ece3.2866] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 02/01/2017] [Accepted: 02/06/2017] [Indexed: 11/13/2022] Open
Abstract
The differential discrimination of nitrogen isotopes (15N/14N) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the 15N/14N of amino acids (δ15 NAA) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the δ15 NAA values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (=1.0 ± 0.1, mean ± 1σ). However, the estimated TPs of flowers varied significantly (Type I: 2.2 ± 0.2; Type II: 1.0 ± 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind 15N in the residual pool of amino acids; and (3) the incorporation of these 15N-enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the δ15 NAA values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers.
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Affiliation(s)
- Yuko Takizawa
- Faculty of Environmental Earth Science Hokkaido University Sapporo Japan
- Institute of Low Temperature Science Hokkaido University Sapporo Japan
- Japan Agency for Marine-Earth Science and Technology Yokosuka Japan
| | | | - Shawn A Steffan
- Department of Entomology University of Wisconsin Madison WI USA
- US Department of Agriculture Agricultural Research Service Madison WI USA
| | - Yoshinori Takano
- Japan Agency for Marine-Earth Science and Technology Yokosuka Japan
| | - Naohiko Ohkouchi
- Japan Agency for Marine-Earth Science and Technology Yokosuka Japan
| | - Yoshito Chikaraishi
- Institute of Low Temperature Science Hokkaido University Sapporo Japan
- Japan Agency for Marine-Earth Science and Technology Yokosuka Japan
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26
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Hebert CE, Popp BN, Fernie KJ, Ka'apu-Lyons C, Rattner BA, Wallsgrove N. Amino Acid Specific Stable Nitrogen Isotope Values in Avian Tissues: Insights from Captive American Kestrels and Wild Herring Gulls. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:12928-12937. [PMID: 27786442 DOI: 10.1021/acs.est.6b04407] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Through laboratory and field studies, the utility of amino acid compound-specific nitrogen isotope analysis (AA-CSIA) in avian studies is investigated. Captive American kestrels (Falco sparverius) were fed an isotopically characterized diet and patterns in δ15N values of amino acids (AAs) were compared to those in their tissues (muscle and red blood cells) and food. Based upon nitrogen isotope discrimination between diet and kestrel tissues, AAs could mostly be categorized as source AAs (retaining baseline δ15N values) and trophic AAs (showing 15N enrichment). Trophic discrimination factors based upon the source (phenylalanine, Phe) and trophic (glutamic acid, Glu) AAs were 4.1 (muscle) and 5.4 (red blood cells), lower than those reported for metazoan invertebrates. In a field study involving omnivorous herring gulls (Larus argentatus smithsonianus), egg AA isotopic patterns largely retained those observed in the laying female's tissues (muscle, red blood cells, and liver). Realistic estimates of gull trophic position were obtained using bird Glu and Phe δ15N values combined with β values (difference in Glu and Phe δ15N in primary producers) for aquatic and terrestrial food webs. Egg fatty acids were used to weight β values for proportions of aquatic and terrestrial food in gull diets. This novel approach can be applied to generalist species that feed across ecosystem boundaries.
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Affiliation(s)
- C E Hebert
- Environment and Climate Change Canada, Science and Technology Branch, National Wildlife Research Centre , Ottawa, ON K1A 0H3, Canada
| | - B N Popp
- Department of Geology and Geophysics, University of Hawaii , Honolulu, Hawaii 96822, United States
| | - K J Fernie
- Environment and Climate Change Canada, Science and Technology Branch, Canada Centre for Inland Waters , Burlington, ON L7R 4A6, Canada
| | - C Ka'apu-Lyons
- Department of Geology and Geophysics, University of Hawaii , Honolulu, Hawaii 96822, United States
| | - B A Rattner
- United States Geological Survey, Patuxent Wildlife Research Center , Beltsville, Maryland 20705, United States
| | - N Wallsgrove
- Department of Geology and Geophysics, University of Hawaii , Honolulu, Hawaii 96822, United States
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27
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Middelburg JJ, Mueller CE, Veuger B, Larsson AI, Form A, van Oevelen D. Discovery of symbiotic nitrogen fixation and chemoautotrophy in cold-water corals. Sci Rep 2015; 5:17962. [PMID: 26644069 PMCID: PMC4672307 DOI: 10.1038/srep17962] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 11/09/2015] [Indexed: 11/17/2022] Open
Abstract
Cold-water corals (CWC) are widely distributed around the world forming extensive reefs at par with tropical coral reefs. They are hotspots of biodiversity and organic matter processing in the world’s deep oceans. Living in the dark they lack photosynthetic symbionts and are therefore considered to depend entirely on the limited flux of organic resources from the surface ocean. While symbiotic relations in tropical corals are known to be key to their survival in oligotrophic conditions, the full metabolic capacity of CWC has yet to be revealed. Here we report isotope tracer evidence for efficient nitrogen recycling, including nitrogen assimilation, regeneration, nitrification and denitrification. Moreover, we also discovered chemoautotrophy and nitrogen fixation in CWC and transfer of fixed nitrogen and inorganic carbon into bulk coral tissue and tissue compounds (fatty acids and amino acids). This unrecognized yet versatile metabolic machinery of CWC conserves precious limiting resources and provides access to new nitrogen and organic carbon resources that may be essential for CWC to survive in the resource-depleted dark ocean.
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Affiliation(s)
- Jack J Middelburg
- Department of Earth Sciences, Utrecht University, P.O. Box 80.021, 3508 TA Utrecht, The Netherlands
| | - Christina E Mueller
- Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), P.O. Box 140, 4400 AC Yerseke, The Netherlands
| | - Bart Veuger
- Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), P.O. Box 140, 4400 AC Yerseke, The Netherlands
| | - Ann I Larsson
- Dept. of Marine Sciences, Tjärnö, University of Gothenburg, 452 96 Strömstad, Sweden
| | - Armin Form
- GEOMAR, Helmholtz Centre for Ocean Research, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Dick van Oevelen
- Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), P.O. Box 140, 4400 AC Yerseke, The Netherlands
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McMahon KW, McCarthy MD, Sherwood OA, Larsen T, Guilderson TP. Millennial-scale plankton regime shifts in the subtropical North Pacific Ocean. Science 2015; 350:1530-3. [DOI: 10.1126/science.aaa9942] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 11/06/2015] [Indexed: 11/02/2022]
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29
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Hussey NE, MacNeil MA, Siple MC, Popp BN, Dudley SF, Fisk AT. Expanded trophic complexity among large sharks. FOOD WEBS 2015. [DOI: 10.1016/j.fooweb.2015.04.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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30
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Sackett DK, Drazen JC, Choy CA, Popp B, Pitz GL. Mercury sources and trophic ecology for Hawaiian bottomfish. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:6909-6918. [PMID: 25936419 DOI: 10.1021/acs.est.5b01009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In Hawaii, some of the most important commercial and recreational fishes comprise an assemblage of lutjanids and carangids called bottomfish. Despite their importance, we know little about their trophic ecology or where the mercury (Hg) that ultimately resides in their tissue originates. Here we investigated these topics, by analyzing muscle samples for mercury content, nitrogen, carbon, and amino acid specific nitrogen isotope ratios in six species distributed across different depths from the Northwestern Hawaiian Islands (NWHI) and the Main Hawaiian Islands (MHI). Fishes had different sources of nitrogen and carbon, with isotopic values suggesting benthic food sources for shallow nearshore species. High trophic position lutjanids that foraged in deeper water, benthic environments generally had higher Hg levels. Model results also suggested that benthic Hg methylation was an important source of Hg for shallow benthic feeders, while deepwater sources of mercury may be important for those with a diet that derives, at least in part, from the pelagic environment. Further, despite the lack of freshwater sources of Hg in the NWHI, statistical models explaining the variation in tissue Hg in the MHI and NWHI were nearly identical, suggesting freshwater Hg inputs were not a major source of Hg in fish tissue.
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Affiliation(s)
- Dana K Sackett
- †Department of Oceanography, University of Hawaii, Manoa, 1000 Pope Road, Honolulu, Hawaii 96822, United States
| | - Jeffrey C Drazen
- †Department of Oceanography, University of Hawaii, Manoa, 1000 Pope Road, Honolulu, Hawaii 96822, United States
| | - C Anela Choy
- †Department of Oceanography, University of Hawaii, Manoa, 1000 Pope Road, Honolulu, Hawaii 96822, United States
- ‡Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, United States
| | - Brian Popp
- §Department of Geology and Geophysics, University of Hawaii, Manoa, 1680 East-West Road, Honolulu, Hawaii 96822, United States
| | - Gerald L Pitz
- ∥Hawaii Department of Health, State Laboratory Division, 2725 Waimano Home Road, Pearl City, Hawaii 96782, United States
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Chikaraishi Y, Steffan SA, Takano Y, Ohkouchi N. Diet quality influences isotopic discrimination among amino acids in an aquatic vertebrate. Ecol Evol 2015; 5:2048-59. [PMID: 26045955 PMCID: PMC4449758 DOI: 10.1002/ece3.1491] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 03/03/2015] [Accepted: 03/10/2015] [Indexed: 11/07/2022] Open
Abstract
Stable nitrogen isotopic composition of amino acids (δ (15)NAA) has recently been employed as a powerful tool in ecological food web studies, particularly for estimating the trophic position (TP) of animal species in food webs. However, the validity of these estimates depends on the consistency of the trophic discrimination factor (TDF; - Δδ (15)NAA at each shift of trophic level) among a suite of amino acids within the tissues of consumer species. In this study, we determined the TDF values of amino acids in tadpoles (the Japanese toad, Bufo japonicus) reared exclusively on one of three diets that differed in nutritional quality. The diets were commercial fish-food pellets (plant and animal biomass), bloodworms (animal biomass), and boiled white rice (plant carbohydrate), representing a balanced, protein-rich, and protein-poor diet, respectively. The TDF values of two "source amino acids" (Src-AAs), methionine and phenylalanine, were close to zero (0.3-0.5‰) among the three diets, typifying the values reported in the literature (∼0.5‰ and ∼0.4‰, respectively). However, TDF values of "trophic amino acids" (Tr-AAs) including alanine, valine, leucine, isoleucine, and glutamic acid varied by diet: for example, the glutamic acid TDF was similar to the standard value (∼8.0‰) when tadpoles were fed either the commercial pellets (8.0‰) or bloodworms (7.9‰), but when they were fed boiled rice, the TDF was significantly reduced (0.6‰). These results suggest that a profound lack of dietary protein may alter the TDF values of glutamic acid (and other Tr-AAs and glycine) within consumer species, but not the two Src-AAs (i.e., methionine and phenylalanine). Knowledge of how a nutritionally poor diet can influence the TDF of Tr- and Src-AAs will allow amino acid isotopic analyses to better estimate TP among free-roaming animals.
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Affiliation(s)
- Yoshito Chikaraishi
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Shawn A Steffan
- USDA-ARS Vegetable Crops Research Unit, Department of Entomology, University of Wisconsin 1630 Linden Dr., Madison, WI, USA
| | - Yoshinori Takano
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Naohiko Ohkouchi
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
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32
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Meta-analysis of amino acid stable nitrogen isotope ratios for estimating trophic position in marine organisms. Oecologia 2015; 178:631-42. [DOI: 10.1007/s00442-015-3305-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 03/19/2015] [Indexed: 10/23/2022]
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Brault EK, Koch PL, Gier E, Ruiz-Cooley RI, Zupcic J, Gilbert KN, McCarthy MD. Effects of decalcification on bulk and compound-specific nitrogen and carbon isotope analyses of dentin. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2014; 28:2744-2752. [PMID: 25380497 DOI: 10.1002/rcm.7073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/07/2014] [Accepted: 10/08/2014] [Indexed: 06/04/2023]
Abstract
RATIONALE For bulk carbon and nitrogen isotope analysis of dentin, samples are typically decalcified. Since the non-protein carbon in dentin is low, whole sample analysis may produce reliable data. Compound-specific isotope analysis (CSIA) of bone and tooth dentin protein is a powerful tool for reconstructing the flow of carbon and nitrogen in modern and past food webs. Decalcification has also been used to prepare bone and dentin samples for CSIA, but the effects of this process on bulk dentin, amino acid composition, and their specific isotope values are not known. METHODS The bulk isotope values of raw and decalcified dentin from a sperm whale tooth were measured to determine the effects of decalcification and the accuracy of untreated dentin results. CSIA was also performed on decalcified and raw dentin to examine differences in the amino acid isotope values and molar composition between these two approaches. RESULTS Analysis of raw dentin yields precise and accurate bulk isotope measurements for this animal. The isotopic values of decalcified samples and raw dentin for individual amino acids were similar, but the average of the isotope value offsets between the two sample types was significant. The presence of inorganic material complicated raw sample processing for individual amino acid isotope values, and may have contributed to the isotopic differences between decalcified and raw samples. CONCLUSIONS Decalcification is not needed to measure bulk isotope values in dentin from this modern odontocete, probably because the lipid and carbonate concentrations are low and the carbon isotope values of dentin protein and carbonate are similar. This method should not be applied in some cases (e.g., with fossil dentin and modern bone). Decalcification should still be used prior to CSIA since significant matrix issues occur with raw dentin processing and decalcification does not alter the amino acid molar composition or isotopic values of dentin.
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Affiliation(s)
- Emily K Brault
- University of California, Santa Cruz, Ocean Sciences Department, 1156 High Street, Santa Cruz, CA, 95064, USA
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Ruiz-Cooley RI, Koch PL, Fiedler PC, McCarthy MD. Carbon and nitrogen isotopes from top predator amino acids reveal rapidly shifting ocean biochemistry in the outer California Current. PLoS One 2014; 9:e110355. [PMID: 25329915 PMCID: PMC4201512 DOI: 10.1371/journal.pone.0110355] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 09/20/2014] [Indexed: 11/19/2022] Open
Abstract
Climatic variation alters biochemical and ecological processes, but it is difficult both to quantify the magnitude of such changes, and to differentiate long-term shifts from inter-annual variability. Here, we simultaneously quantify decade-scale isotopic variability at the lowest and highest trophic positions in the offshore California Current System (CCS) by measuring δ15N and δ13C values of amino acids in a top predator, the sperm whale (Physeter macrocephalus). Using a time series of skin tissue samples as a biological archive, isotopic records from individual amino acids (AAs) can reveal the proximate factors driving a temporal decline we observed in bulk isotope values (a decline of ≥1 ‰) by decoupling changes in primary producer isotope values from those linked to the trophic position of this toothed whale. A continuous decline in baseline (i.e., primary producer) δ15N and δ13C values was observed from 1993 to 2005 (a decrease of ∼4‰ for δ15N source-AAs and 3‰ for δ13C essential-AAs), while the trophic position of whales was variable over time and it did not exhibit directional trends. The baseline δ15N and δ13C shifts suggest rapid ongoing changes in the carbon and nitrogen biogeochemical cycling in the offshore CCS, potentially occurring at faster rates than long-term shifts observed elsewhere in the Pacific. While the mechanisms forcing these biogeochemical shifts remain to be determined, our data suggest possible links to natural climate variability, and also corresponding shifts in surface nutrient availability. Our study demonstrates that isotopic analysis of individual amino acids from a top marine mammal predator can be a powerful new approach to reconstructing temporal variation in both biochemical cycling and trophic structure.
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Affiliation(s)
- Rocio I. Ruiz-Cooley
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, California, United States of America
- * E-mail:
| | - Paul L. Koch
- Earth and Planetary Sciences Department, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Paul C. Fiedler
- Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America
| | - Matthew D. McCarthy
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, California, United States of America
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Madigan DJ, Baumann Z, Carlisle AB, Hoen DK, Popp BN, Dewar H, Snodgrass OE, Block BA, Fisher NS. Reconstructing transoceanic migration patterns of Pacific bluefin tuna using a chemical tracer toolbox. Ecology 2014; 95:1674-83. [PMID: 25039231 DOI: 10.1890/13-1467.1] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Large pelagic predators play important roles in oceanic ecosystems, and may migrate vast distances to utilize resources in different marine ecoregions. Understanding movement patterns of migratory marine animals is critical for effective management, but often challenging, due to the cryptic habitat of pelagic migrators and the difficulty of assessing past movements. Chemical tracers can partially circumvent these challenges by reconstructing recent migration patterns. Pacific bluefin tuna (Thunnus orientalis; PBFT) inhabit the western and eastern Pacific Ocean, and are in steep decline due to overfishing. Understanding age-specific eastward transpacific migration patterns can improve management practices, but these migratory dynamics remain largely unquantified. Here, we combine a Fukushima-derived radiotracer (134Cs) with bulk tissue and amino acid stable isotope analyses of PBFT to distinguish recent migrants from residents of the eastern Pacific Ocean. The proportion of recent migrants to residents decreased in older year classes, though the proportion of older PBFT that recently migrated across the Pacific was greater than previous estimates. This novel toolbox of biogeochemical tracers can be applied to any species that crosses the North Pacific Ocean.
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36
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Chikaraishi Y, Steffan SA, Ogawa NO, Ishikawa NF, Sasaki Y, Tsuchiya M, Ohkouchi N. High-resolution food webs based on nitrogen isotopic composition of amino acids. Ecol Evol 2014; 4:2423-49. [PMID: 25360278 PMCID: PMC4203290 DOI: 10.1002/ece3.1103] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 04/09/2014] [Accepted: 04/15/2014] [Indexed: 11/12/2022] Open
Abstract
Food webs are known to have myriad trophic links between resource and consumer species. While herbivores have well-understood trophic tendencies, the difficulties associated with characterizing the trophic positions of higher-order consumers have remained a major problem in food web ecology. To better understand trophic linkages in food webs, analysis of the stable nitrogen isotopic composition of amino acids has been introduced as a potential means of providing accurate trophic position estimates. In the present study, we employ this method to estimate the trophic positions of 200 free-roaming organisms, representing 39 species in coastal marine (a stony shore) and 38 species in terrestrial (a fruit farm) environments. Based on the trophic positions from the isotopic composition of amino acids, we are able to resolve the trophic structure of these complex food webs. Our approach reveals a high degree of trophic omnivory (i.e., noninteger trophic positions) among carnivorous species such as marine fish and terrestrial hornets.This information not only clarifies the trophic tendencies of species within their respective communities, but also suggests that trophic omnivory may be common in these webs.
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Affiliation(s)
- Yoshito Chikaraishi
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Shawn A Steffan
- USDA-ARS Vegetable Crops Research Unit, 1630 Linden Dr., Department of Entomology, University of Wisconsin Madison, WI, 53706, USA
| | - Nanako O Ogawa
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Naoto F Ishikawa
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Yoko Sasaki
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Masashi Tsuchiya
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
| | - Naohiko Ohkouchi
- Japan Agency for Marine-Earth Science and Technology 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan
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Cappuccio JA, Falso MJS, Kashgarian M, Buchholz BA. 14C Analysis of protein extracts from Bacillus spores. Forensic Sci Int 2014; 240:54-60. [PMID: 24814329 DOI: 10.1016/j.forsciint.2014.04.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 10/25/2022]
Abstract
Investigators of bioagent incidents or interdicted materials need validated, independent analytical methods that will allow them to distinguish between recently made bioagent samples versus material drawn from the archives of a historical program. Heterotrophic bacteria convert the carbon in their food sources, growth substrate or culture media, into the biomolecules they need. The F(14)C (fraction modern radiocarbon) of a variety of media, Bacillus spores, and separated proteins from Bacillus spores was measured by accelerator mass spectrometry (AMS). AMS precisely measures F(14)C values of biological materials and has been used to date the synthesis of biomaterials over the bomb pulse era (1955 to present). The F(14)C of Bacillus spores reflects the radiocarbon content of the media in which they were grown. In a survey of commercial media we found that the F(14)C value indicated that carbon sources for the media were alive within about a year of the date of manufacture and generally of terrestrial origin. Hence, bacteria and their products can be dated using their (14)C signature. Bacillus spore samples were generated onsite with defined media and carbon free purification and also obtained from archived material. Using mechanical lysis and a variety of washes with carbon free acids and bases, contaminant carbon was removed from soluble proteins to enable accurate (14)C bomb-pulse dating. Since media is contemporary, (14)C bomb-pulse dating of isolated soluble proteins can be used to distinguish between historical archives of bioagents and those produced from recent media.
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Affiliation(s)
- Jenny A Cappuccio
- Biosciences & Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Miranda J Sarachine Falso
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Michaele Kashgarian
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States
| | - Bruce A Buchholz
- Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94551, United States.
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38
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Bradley CJ, Madigan DJ, Block BA, Popp BN. Amino acid isotope incorporation and enrichment factors in Pacific bluefin tuna, Thunnus orientalis. PLoS One 2014; 9:e85818. [PMID: 24465724 PMCID: PMC3899081 DOI: 10.1371/journal.pone.0085818] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 12/02/2013] [Indexed: 11/18/2022] Open
Abstract
Compound specific isotopic analysis (CSIA) of amino acids has received increasing attention in ecological studies in recent years due to its ability to evaluate trophic positions and elucidate baseline nutrient sources. However, the incorporation rates of individual amino acids into protein and specific trophic discrimination factors (TDFs) are largely unknown, limiting the application of CSIA to trophic studies. We determined nitrogen turnover rates of individual amino acids from a long-term (up to 1054 days) laboratory experiment using captive Pacific bluefin tuna, Thunnus orientalis (PBFT), a large endothermic pelagic fish fed a controlled diet. Small PBFT (white muscle δ(15)N∼11.5‰) were collected in San Diego, CA and transported to the Tuna Research and Conservation Center (TRCC) where they were fed a controlled diet with high δ(15)N values relative to PBFT white muscle (diet δ(15)N∼13.9‰). Half-lives of trophic and source amino acids ranged from 28.6 to 305.4 days and 67.5 to 136.2 days, respectively. The TDF for the weighted mean values of amino acids was 3.0 ‰, ranging from 2.2 to 15.8 ‰ for individual combinations of 6 trophic and 5 source amino acids. Changes in the δ(15)N values of amino acids across trophic levels are the underlying drivers of the trophic (15)N enrichment. Nearly all amino acid δ(15)N values in this experiment changed exponentially and could be described by a single compartment model. Significant differences in the rate of (15)N incorporation were found for source and trophic amino acids both within and between these groups. Varying half-lives of individual amino acids can be applied to migratory organisms as isotopic clocks, determining the length of time an individual has spent in a new environment. These results greatly enhance the ability to interpret compound specific isotope analyses in trophic studies.
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Affiliation(s)
- Christina J. Bradley
- Department of Oceanography, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Daniel J. Madigan
- Tuna Research and Conservation Center, Pacific Grove, California, United States of America
- Stanford University, Hopkins Marine Station, Pacific Grove, California, United States of America
| | - Barbara A. Block
- Monterey Bay Aquarium, Monterey, California, United States of America
| | - Brian N. Popp
- Department of Geology and Geophysics, University of Hawaii, Honolulu, Hawaii, United States of America
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Increasing subtropical North Pacific Ocean nitrogen fixation since the Little Ice Age. Nature 2013; 505:78-81. [DOI: 10.1038/nature12784] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 10/02/2013] [Indexed: 11/08/2022]
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Broek TAB, Walker BD, Andreasen DH, McCarthy MD. High-precision measurement of phenylalanine δ15N values for environmental samples: a new approach coupling high-pressure liquid chromatography purification and elemental analyzer isotope ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2013; 27:2327-2337. [PMID: 24097388 DOI: 10.1002/rcm.6695] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/19/2013] [Accepted: 07/20/2013] [Indexed: 06/02/2023]
Abstract
RATIONALE Compound-specific isotope analysis of individual amino acids (CSI-AA) is a powerful new tool for tracing nitrogen (N) source and transformation in biogeochemical cycles. Specifically, the δ(15)N value of phenylalanine (δ(15)N(Phe)) represents an increasingly used proxy for source δ(15)N signatures, with particular promise for paleoceanographic applications. However, current derivatization/gas chromatography methods require expensive and relatively uncommon instrumentation, and have relatively low precision, making many potential applications impractical. METHODS A new offline approach has been developed for high-precision δ(15)N measurements of amino acids (δ(15)N(AA)), optimized for δ(15)N(Phe) values. Amino acids (AAs) are first purified via high-pressure liquid chromatography (HPLC), using a mixed-phase column and automated fraction collection. The δ(15)N values are determined via offline elemental analyzer-isotope ratio mass spectrometry (EA-IRMS). RESULTS The combined HPLC/EA-IRMS method separated most protein AAs with sufficient resolution to obtain accurate δ(15)N values, despite significant intra-peak isotopic fractionation. For δ(15)N(Phe) values, the precision was ±0.16‰ for standards, 4× better than gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS; ±0.64‰). We also compared a δ(15)N(Phe) paleo-record from a deep-sea bamboo coral from Monterey Bay, CA, USA, using our method versus GC/C/IRMS. The two methods produced equivalent δ(15)N(Phe) values within error; however, the δ(15)N(Phe) values from HPLC/EA-IRMS had approximately twice the precision of GC/C/IRMS (average stdev of 0.27‰ ± 0.14‰ vs 0.60‰ ± 0.20‰, respectively). CONCLUSIONS These results demonstrate that offline HPLC represents a viable alternative to traditional GC/C/IMRS for δ(15)N(AA) measurement. HPLC/EA-IRMS is more precise and widely available, and therefore useful in applications requiring increased precision for data interpretation (e.g. δ(15)N paleoproxies).
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Affiliation(s)
- Taylor A B Broek
- Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
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Range expansion of the jumbo squid in the NE Pacific: δ15N decrypts multiple origins, migration and habitat use. PLoS One 2013; 8:e59651. [PMID: 23527242 PMCID: PMC3601055 DOI: 10.1371/journal.pone.0059651] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 02/16/2013] [Indexed: 11/25/2022] Open
Abstract
Coincident with climate shifts and anthropogenic perturbations, the highly voracious jumbo squid Dosidicus gigas reached unprecedented northern latitudes along the NE Pacific margin post 1997–98. The physical or biological drivers of this expansion, as well as its ecological consequences remain unknown. Here, novel analysis from both bulk tissues and individual amino acids (Phenylalanine; Phe and Glutamic acid; Glu) in both gladii and muscle of D. gigas captured in the Northern California Current System (NCCS) documents for the first time multiple geographic origins and migration. Phe δ15N values, a proxy for habitat baseline δ15N values, confirm at least three different geographic origins that were initially detected by highly variable bulk δ15N values in gladii for squid at small sizes (<30 cm gladii length). In contrast, bulk δ15N values from gladii of large squid (>60 cm) converged, indicating feeding in a common ecosystem. The strong latitudinal gradient in Phe δ15N values from composite muscle samples further confirmed residency at a point in time for large squid in the NCCS. These results contrast with previous ideas, and indicate that small squid are highly migratory, move into the NCCS from two or more distinct geographic origins, and use this ecosystem mainly for feeding. These results represent the first direct information on the origins, immigration and habitat use of this key “invasive” predator in the NCCS, with wide implications for understanding both the mechanisms of periodic D. gigas population range expansions, and effects on ecosystem trophic structure.
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Lefort S, Gratton Y, Mucci A, Dadou I, Gilbert D. Hypoxia in the Lower St. Lawrence Estuary: How physics controls spatial patterns. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011jc007751] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Seminoff JA, Benson SR, Arthur KE, Eguchi T, Dutton PH, Tapilatu RF, Popp BN. Stable isotope tracking of endangered sea turtles: validation with satellite telemetry and δ15N analysis of amino acids. PLoS One 2012; 7:e37403. [PMID: 22666354 PMCID: PMC3362573 DOI: 10.1371/journal.pone.0037403] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 04/19/2012] [Indexed: 11/18/2022] Open
Abstract
Effective conservation strategies for highly migratory species must incorporate information about long-distance movements and locations of high-use foraging areas. However, the inherent challenges of directly monitoring these factors call for creative research approaches and innovative application of existing tools. Highly migratory marine species, such as marine turtles, regularly travel hundreds or thousands of kilometers between breeding and feeding areas, but identification of migratory routes and habitat use patterns remains elusive. Here we use satellite telemetry in combination with compound-specific isotope analysis of amino acids to confirm that insights from bulk tissue stable isotope analysis can reveal divergent migratory strategies and within-population segregation of foraging groups of critically endangered leatherback sea turtles (Dermochelys coriacea) across the Pacific Ocean. Among the 78 turtles studied, we found a distinct dichotomy in δ15N values of bulk skin, with distinct “low δ15N” and “high δ15N” groups. δ15N analysis of amino acids confirmed that this disparity resulted from isotopic differences at the base of the food chain and not from differences in trophic position between the two groups. Satellite tracking of 13 individuals indicated that their bulk skin δ15N value was linked to the particular foraging region of each turtle. These findings confirm that prevailing marine isoscapes of foraging areas can be reflected in the isotopic compositions of marine turtle body tissues sampled at nesting beaches. We use a Bayesian mixture model to show that between 82 and 100% of the 78 skin-sampled turtles could be assigned with confidence to either the eastern Pacific or western Pacific, with 33 to 66% of all turtles foraging in the eastern Pacific. Our forensic approach validates the use of stable isotopes to depict leatherback turtle movements over broad spatial ranges and is timely for establishing wise conservation efforts in light of this species’ imminent risk of extinction in the Pacific.
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Affiliation(s)
- Jeffrey A Seminoff
- National Oceanic and Atmospheric Administration-National Marine Fisheries Service, Southwest Fisheries Science Center, La Jolla, California, United States of America.
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Three decades of high-resolution coastal sea surface temperatures reveal more than warming. Nat Commun 2012; 3:704. [PMID: 22426225 DOI: 10.1038/ncomms1713] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2011] [Accepted: 01/30/2012] [Indexed: 11/09/2022] Open
Abstract
Understanding and forecasting current and future consequences of coastal warming require a fine-scale assessment of the near-shore temperature changes. Here we show that despite the fact that 71% of the world's coastlines are significantly warming, rates of change have been highly heterogeneous both spatially and seasonally. We demonstrate that 46% of the coastlines have experienced a significant decrease in the frequency of extremely cold events, while extremely hot days are becoming more common in 38% of the area. Also, we show that the onset of the warm season is significantly advancing earlier in the year in 36% of the temperate coastal regions. More importantly, it is now possible to analyse local patterns within the global context, which is useful for a broad array of scientific fields, policy makers and general public.
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