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de la Iglesia-Vélez B, Díaz-Pérez L, Acuña JL, Morán XAG. Spatial and seasonal variability of picoplankton abundance and growth rates in the southern Bay of Biscay. MARINE ENVIRONMENTAL RESEARCH 2024; 194:106331. [PMID: 38181718 DOI: 10.1016/j.marenvres.2023.106331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 12/21/2023] [Accepted: 12/27/2023] [Indexed: 01/07/2024]
Abstract
Autotrophic and heterotrophic picoplankton play fundamental roles in marine food webs and biogeochemical cycles. However, their growth responses have seldom been jointly assessed, including many temperate regions such as the Bay of Biscay. There, previous studies have shown their relevance in carbon fluxes. We describe here the spatio-temporal variability of the abundances and growth rates of the picoplanktonic groups routinely distinguished by flow cytometry (Synechococcus and Prochlorococcus cyanobacteria, two groups of differently sized picoeukaryotes and two groups of heterotrophic bacteria distinguished by their relative nucleic acid content) in the central Cantabrian Sea (S Bay of Biscay). To that end, from February to December 2021 we collected surface water on 5 occasions from 6 stations distributed along the S Bay of Biscay (6-3°W) and incubated it after removing protistan grazers in order to determine their dynamics along the seasonal cycle as well as the inshore-offshore and the west-east gradients. Seasonal variations in initial and maximum abundances generally matched previous knowledge of the region but growth rates were more variable, with Prochlorococcus and high nucleic acid (HNA) bacteria showing the maximum values (up to 2 d-1) while negative growth was observed in one third of Synechococcus incubations. Temporal differences generally overrode differences along the inshore-offshore gradient in trophic status while in situ and maximum abundances of most of the groups generally decreased towards the east following the increase in stratification and lower nutrient availability. Responses to stratification suggest Prochlorococcus and low nucleic acid (LNA) cells may prevail among autotrophic and heterotrophic bacteria, respectively, in a warmer ocean.
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Affiliation(s)
| | - Laura Díaz-Pérez
- Centro Oceanográfico de Gijón/Xixón (IEO-CSIC), 33212, Gijón/Xixón, Spain
| | - José Luis Acuña
- Departamento de Biología de Organismos y Sistemas, Universidad de Oviedo/Uviéu, 33071, Oviedo/Uviéu, Spain
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2
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Sabbagh EI, Calleja ML, Daffonchio D, Morán XAG. Seasonality of top-down control of bacterioplankton at two central Red Sea sites with different trophic status. Environ Microbiol 2023; 25:2002-2019. [PMID: 37286523 DOI: 10.1111/1462-2920.16439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Accepted: 05/22/2023] [Indexed: 06/09/2023]
Abstract
The role of bottom-up (nutrient availability) and top-down (grazers and viruses mortality) controls on tropical bacterioplankton have been rarely investigated simultaneously from a seasonal perspective. We have assessed them through monthly samplings over 2 years in inshore and offshore waters of the central Red Sea differing in trophic status. Flow cytometric analysis allowed us to distinguish five groups of heterotrophic bacteria based on physiological properties (nucleic acid content, membrane integrity and active respiration), three groups of cyanobacteria (two populations of Synechococcus and Prochlorococcus), heterotrophic nanoflagellates (HNFs) and three groups of viruses based on nucleic acid content. The dynamics of bacterioplankton and their top-down controls varied with season and location, being more pronounced in inshore waters. HNFs abundances showed a strong preference for larger prey inshore (r = -0.62 to -0.59, p = 0.001-0.002). Positive relationships between viruses and heterotrophic bacterioplankton abundances were more marked inshore (r = 0.67, p < 0.001) than offshore (r = 0.44, p = 0.03). The negative correlation between HNFs and viruses abundances (r = -0.47, p = 0.02) in shallow waters indicates a persistent seasonal switch between protistan grazing and viral lysis that maintains the low bacterioplankton stocks in the central Red Sea area.
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Affiliation(s)
- Eman I Sabbagh
- Red Sea Research Center (RSRC), Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Maria Ll Calleja
- Red Sea Research Center (RSRC), Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
- Department of Climate Geochemistry, Max Plank Institute for Chemistry (MPIC), Mainz, Germany
| | - Daniele Daffonchio
- Red Sea Research Center (RSRC), Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Xosé Anxelu G Morán
- Red Sea Research Center (RSRC), Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
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3
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Kamalanathan M, Schwehr KA, Labonté JM, Taylor C, Bergen C, Patterson N, Claflin N, Santschi PH, Quigg A. The Interplay of Phototrophic and Heterotrophic Microbes Under Oil Exposure: A Microcosm Study. Front Microbiol 2021; 12:675328. [PMID: 34408728 PMCID: PMC8366316 DOI: 10.3389/fmicb.2021.675328] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 06/28/2021] [Indexed: 11/18/2022] Open
Abstract
Microbial interactions influence nearly one-half of the global biogeochemical flux of major elements of the marine ecosystem. Despite their ecological importance, microbial interactions remain poorly understood and even less is known regarding the effects of anthropogenic perturbations on these microbial interactions. The Deepwater Horizon oil spill exposed the Gulf of Mexico to ∼4.9 million barrels of crude oil over 87 days. We determined the effects of oil exposure on microbial interactions using short- and long-term microcosm experiments with and without Macondo surrogate oil. Microbial activity determined using radiotracers revealed that oil exposure negatively affected substrate uptake by prokaryotes within 8 h and by eukaryotes over 72 h. Eukaryotic uptake of heterotrophic exopolymeric substances (EPS) was more severely affected than prokaryotic uptake of phototrophic EPS. In addition, our long-term exposure study showed severe effects on photosynthetic activity. Lastly, changes in microbial relative abundances and fewer co-occurrences among microbial species were mostly driven by photosynthetic activity, treatment (control vs. oil), and prokaryotic heterotrophic metabolism. Overall, oil exposure affected microbial co-occurrence and/or interactions possibly by direct reduction in abundance of one of the interacting community members and/or indirect by reduction in metabolism (substrate uptake or photosynthesis) of interacting members.
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Affiliation(s)
- Manoj Kamalanathan
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, United States
| | - Kathleen A Schwehr
- Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX, United States
| | - Jessica M Labonté
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, United States
| | - Christian Taylor
- Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX, United States
| | - Charles Bergen
- Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX, United States
| | - Nicole Patterson
- Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX, United States
| | - Noah Claflin
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, United States
| | - Peter H Santschi
- Department of Marine and Coastal Environmental Science, Texas A&M University at Galveston, Galveston, TX, United States.,Department of Oceanography, Texas A&M University, College Station, TX, United States
| | - Antonietta Quigg
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, United States.,Department of Oceanography, Texas A&M University, College Station, TX, United States
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Sabbagh EI, Huete-Stauffer TM, Calleja MLL, Silva L, Viegas M, Morán XAG. Weekly variations of viruses and heterotrophic nanoflagellates and their potential impact on bacterioplankton in shallow waters of the central Red Sea. FEMS Microbiol Ecol 2020; 96:5800985. [PMID: 32149360 PMCID: PMC7104677 DOI: 10.1093/femsec/fiaa033] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 03/08/2020] [Indexed: 11/14/2022] Open
Abstract
Bacterioplankton play a pivotal role in marine ecosystems. However, their temporal dynamics and underlying control mechanisms are poorly understood in tropical regions such as the Red Sea. Here, we assessed the impact of bottom-up (resource availability) and top-down (viruses and heterotrophic nanoflagellates) controls on bacterioplankton abundances by weekly sampling a coastal central Red Sea site in 2017. We monitored microbial abundances by flow cytometry together with a set of environmental variables including temperature, salinity, dissolved organic and inorganic nutrients and chlorophyll a. We distinguished five groups of heterotrophic bacteria depending on their physiological properties relative nucleic acid content, membrane integrity and cell-specific respiratory activity, two groups of Synechococcus cyanobacteria and three groups of viruses. Viruses controlled heterotrophic bacteria for most of the year, as supported by a negative correlation between their respective abundances and a positive one between bacterial mortality rates and mean viral abundances. On the contrary, heterotrophic nanoflagellates abundance covaried with that of heterotrophic bacteria. Heterotrophic nanoflagellates showed preference for larger bacteria from both the high and low nucleic acid content groups. Our results demonstrate that top-down control is fundamental in keeping heterotrophic bacterioplankton abundances low (< 5 × 10 5 cells mL−1) in Red Sea coastal waters.
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Affiliation(s)
- Eman I Sabbagh
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia
| | - Tamara M Huete-Stauffer
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia
| | - Maria L L Calleja
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia.,Max Planck Institute for Chemistry, Hahn-Meitner Weg 1, 55128 Mainz, Germany
| | - Luis Silva
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia
| | - Miguel Viegas
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia
| | - Xosé Anxelu G Morán
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Kingdom of Saudi Arabia
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Silva L, Calleja ML, Huete-Stauffer TM, Ivetic S, Ansari MI, Viegas M, Morán XAG. Low Abundances but High Growth Rates of Coastal Heterotrophic Bacteria in the Red Sea. Front Microbiol 2019; 9:3244. [PMID: 30666244 PMCID: PMC6330340 DOI: 10.3389/fmicb.2018.03244] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 12/13/2018] [Indexed: 11/29/2022] Open
Abstract
Characterized by some of the highest naturally occurring sea surface temperatures, the Red Sea remains unexplored regarding the dynamics of heterotrophic prokaryotes. Over 16 months, we used flow cytometry to characterize the abundance and growth of four physiological groups of heterotrophic bacteria: membrane-intact (Live), high and low nucleic acid content (HNA and LNA) and actively respiring (CTC+) cells in shallow coastal waters. Chlorophyll a, dissolved organic matter (DOC and DON) concentrations, and their fluorescent properties were also measured as proxies of bottom-up control. We performed short-term incubations (6 days) with the whole microbial community (Community treatment), and with the bacterial community only after removing predators by filtration (Filtered treatment). Initial bacterial abundances ranged from 1.46 to 4.80 × 105 cells mL-1. Total specific growth rates in the Filtered treatment ranged from 0.76 to 2.02 d-1. Live and HNA cells displayed similar seasonal patterns, with higher values during late summer and fall (2.13 and 2.33 d-1, respectively) and lower in late spring (1.02 and 1.01 d-1, respectively). LNA cells were outgrown by the other physiological groups (0.33-1.08 d-1) while CTC+ cells (0.28-1.85 d-1) showed weaker seasonality. The Filtered treatment yielded higher bacterial abundances than the Community treatment in all but 2 of the incubations, and carrying capacities peaked in November 2016 (1.04 × 106 cells mL-1), with minimum values (3.61 × 105 cells mL-1) observed in May 2017. The high temperatures experienced from May through October 2016 (33.4 ± 0.4°C) did not constrain the growth of heterotrophic bacteria. Indeed, bacterial growth efficiencies were positively correlated with environmental temperature, reflecting the presence of more labile compounds (high DON concentrations resulting in lower C:N ratios) in summer. The overall high specific growth rates and the consistently higher carrying capacities in the Filtered treatment suggest that strong top-down control by protistan grazers was the likely cause for the low heterotrophic bacteria abundances.
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Affiliation(s)
- Luis Silva
- Division of Biological and Environmental Sciences and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | | | | | | | | | | | - Xosé Anxelu G. Morán
- Division of Biological and Environmental Sciences and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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6
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Morán XAG, Calvo-Díaz A, Arandia-Gorostidi N, Huete-Stauffer TM. Temperature sensitivities of microbial plankton net growth rates are seasonally coherent and linked to nutrient availability. Environ Microbiol 2018; 20:3798-3810. [PMID: 30159999 DOI: 10.1111/1462-2920.14393] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/24/2018] [Indexed: 11/27/2022]
Abstract
Recent work suggests that temperature effects on marine heterotrophic bacteria are strongly seasonal, but few attempts have been made to concurrently assess them across trophic levels. Here, we estimated the temperature sensitivities (using activation energies, E) of autotrophic and heterotrophic microbial plankton net growth rates over an annual cycle in NE Atlantic coastal waters. Phytoplankton grew in winter and late autumn (0.41 ± 0.16 SE d-1 ) and decayed in the remaining months (-0.42 ± 0.10 d-1 ). Heterotrophic microbes shared a similar seasonality, with positive net growth for bacteria (0.14-1.48 d-1 ), while nanoflagellates had higher values (> 0.4 d-1 ) in winter and spring relative to the rest of the year (-0.46 to 0.29 d-1 ). Net growth rates activation energies showed similar dynamics in the three groups (-1.07 to 1.51 eV), characterized by maxima in winter, minima in summer and resumed increases in autumn. Microbial plankton E values were significantly correlated with nitrate concentrations as a proxy for nutrient availability. Nutrient-sufficiency (i.e., > 1 μmol l-1 nitrate) resulted in significantly higher activation energies of phytoplankton and heterotrophic nanoflagellates relative to nutrient-limited conditions. We suggest that only within spatio-temporal windows of both moderate bottom-up and top-down controls will temperature have a major enhancing effect on microbial growth.
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Affiliation(s)
- Xosé Anxelu G Morán
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Saudi Arabia
| | - Alejandra Calvo-Díaz
- Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía (IEO), Gijón/Xixón, Spain
| | - Nestor Arandia-Gorostidi
- Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía (IEO), Gijón/Xixón, Spain.,Department of Earth System Science, Stanford University, Stanford, CA, USA
| | - Tamara Megan Huete-Stauffer
- King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Biological and Environmental Sciences and Engineering Division, Thuwal, Saudi Arabia.,Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía (IEO), Gijón/Xixón, Spain
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7
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Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem. Ecosystems 2017. [DOI: 10.1007/s10021-017-0208-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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8
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Vick-Majors TJ, Mitchell AC, Achberger AM, Christner BC, Dore JE, Michaud AB, Mikucki JA, Purcell AM, Skidmore ML, Priscu JC. Physiological Ecology of Microorganisms in Subglacial Lake Whillans. Front Microbiol 2016; 7:1705. [PMID: 27833599 PMCID: PMC5081474 DOI: 10.3389/fmicb.2016.01705] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/12/2016] [Indexed: 11/13/2022] Open
Abstract
Subglacial microbial habitats are widespread in glaciated regions of our planet. Some of these environments have been isolated from the atmosphere and from sunlight for many thousands of years. Consequently, ecosystem processes must rely on energy gained from the oxidation of inorganic substrates or detrital organic matter. Subglacial Lake Whillans (SLW) is one of more than 400 subglacial lakes known to exist under the Antarctic ice sheet; however, little is known about microbial physiology and energetics in these systems. When it was sampled through its 800 m thick ice cover in 2013, the SLW water column was shallow (~2 m deep), oxygenated, and possessed sufficient concentrations of C, N, and P substrates to support microbial growth. Here, we use a combination of physiological assays and models to assess the energetics of microbial life in SLW. In general, SLW microorganisms grew slowly in this energy-limited environment. Heterotrophic cellular carbon turnover times, calculated from 3H-thymidine and 3H-leucine incorporation rates, were long (60 to 500 days) while cellular doubling times averaged 196 days. Inferred growth rates (average ~0.006 d-1) obtained from the same incubations were at least an order of magnitude lower than those measured in Antarctic surface lakes and oligotrophic areas of the ocean. Low growth efficiency (8%) indicated that heterotrophic populations in SLW partition a majority of their carbon demand to cellular maintenance rather than growth. Chemoautotrophic CO2-fixation exceeded heterotrophic organic C-demand by a factor of ~1.5. Aerobic respiratory activity associated with heterotrophic and chemoautotrophic metabolism surpassed the estimated supply of oxygen to SLW, implying that microbial activity could deplete the oxygenated waters, resulting in anoxia. We used thermodynamic calculations to examine the biogeochemical and energetic consequences of environmentally imposed switching between aerobic and anaerobic metabolisms in the SLW water column. Heterotrophic metabolisms utilizing acetate and formate as electron donors yielded less energy than chemolithotrophic metabolisms when calculated in terms of energy density, which supports experimental results that showed chemoautotrophic activity in excess of heterotrophic activity. The microbial communities of subglacial lake ecosystems provide important natural laboratories to study the physiological and biogeochemical behavior of microorganisms inhabiting cold, dark environments.
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Affiliation(s)
- Trista J Vick-Majors
- Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA
| | - Andrew C Mitchell
- Department of Geography and Earth Sciences, Aberystwyth University Aberystwyth, UK
| | - Amanda M Achberger
- Department of Biological Sciences, Louisiana State University Baton Rouge, LA, USA
| | - Brent C Christner
- Department of Microbiology and Cell Science, University of FloridaGainesville, FL, USA; Biodiversity Institute, University of FloridaGainesville, FL, USA
| | - John E Dore
- Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA
| | - Alexander B Michaud
- Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA
| | - Jill A Mikucki
- Department of Microbiology, University of Tennessee Knoxville, TN, USA
| | - Alicia M Purcell
- Department of Microbiology, University of Tennessee Knoxville, TN, USA
| | - Mark L Skidmore
- Department of Earth Sciences, Montana State University Bozeman, MT, USA
| | - John C Priscu
- Department of Land Resources and Environmental Sciences, Montana State University Bozeman, MT, USA
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9
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Huete-Stauffer TM, Arandia-Gorostidi N, Alonso-Sáez L, Morán XAG. Experimental Warming Decreases the Average Size and Nucleic Acid Content of Marine Bacterial Communities. Front Microbiol 2016; 7:730. [PMID: 27242747 PMCID: PMC4876119 DOI: 10.3389/fmicb.2016.00730] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/02/2016] [Indexed: 12/16/2022] Open
Abstract
Organism size reduction with increasing temperature has been suggested as a universal response to global warming. Since genome size is usually correlated to cell size, reduction of genome size in unicells could be a parallel outcome of warming at ecological and evolutionary time scales. In this study, the short-term response of cell size and nucleic acid content of coastal marine prokaryotic communities to temperature was studied over a full annual cycle at a NE Atlantic temperate site. We used flow cytometry and experimental warming incubations, spanning a 6°C range, to analyze the hypothesized reduction with temperature in the size of the widespread flow cytometric bacterial groups of high and low nucleic acid content (HNA and LNA bacteria, respectively). Our results showed decreases in size in response to experimental warming, which were more marked in 0.8 μm pre-filtered treatment rather than in the whole community treatment, thus excluding the role of protistan grazers in our findings. Interestingly, a significant effect of temperature on reducing the average nucleic acid content (NAC) of prokaryotic cells in the communities was also observed. Cell size and nucleic acid decrease with temperature were correlated, showing a common mean decrease of 0.4% per °C. The usually larger HNA bacteria consistently showed a greater reduction in cell and NAC compared with their LNA counterparts, especially during the spring phytoplankton bloom period associated to maximum bacterial growth rates in response to nutrient availability. Our results show that the already smallest planktonic microbes, yet with key roles in global biogeochemical cycling, are likely undergoing important structural shrinkage in response to rising temperatures.
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Affiliation(s)
- Tamara M Huete-Stauffer
- Plankton Ecology and Pelagic Ecosystem Dynamics, Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía Gijón/Xixón, Spain
| | - Nestor Arandia-Gorostidi
- Plankton Ecology and Pelagic Ecosystem Dynamics, Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía Gijón/Xixón, Spain
| | - Laura Alonso-Sáez
- Plankton Ecology and Pelagic Ecosystem Dynamics, Centro Oceanográfico de Gijón/Xixón, Instituto Español de OceanografíaGijón/Xixón, Spain; Marine Research Division, AZTISukarrieta, Spain
| | - Xosé Anxelu G Morán
- Plankton Ecology and Pelagic Ecosystem Dynamics, Centro Oceanográfico de Gijón/Xixón, Instituto Español de OceanografíaGijón/Xixón, Spain; Division of Biological and Environmental Sciences and Engineering, Red Sea Research Center, King Abdullah University of Science and TechnologyThuwal, Saudi Arabia
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10
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Sample dilution and bacterial community composition influence empirical leucine-to-carbon conversion factors in surface waters of the world's oceans. Appl Environ Microbiol 2015; 81:8224-32. [PMID: 26407885 DOI: 10.1128/aem.02454-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/15/2015] [Indexed: 11/20/2022] Open
Abstract
The transformation of leucine incorporation rates to prokaryotic carbon production rates requires the use of either theoretical or empirically determined conversion factors. Empirical leucine-to-carbon conversion factors (eCFs) vary widely across environments, and little is known about their potential controlling factors. We conducted 10 surface seawater manipulation experiments across the world's oceans, where the growth of the natural prokaryotic assemblages was promoted by filtration (i.e., removal of grazers [F treatment]) or filtration combined with dilution (i.e., also relieving resource competition [FD treatment]). The impact of sunlight exposure was also evaluated in the FD treatments, and we did not find a significant effect on the eCFs. The eCFs varied from 0.09 to 1.47 kg C mol Leu(-1) and were significantly lower in the FD than in the F samples. Also, changes in bacterial community composition during the incubations, as assessed by automated ribosomal intergenic spacer analysis (ARISA), were more pronounced in the FD than in the F treatments, compared to unmanipulated controls. Thus, we discourage the common procedure of diluting samples (in addition to filtration) for eCF determination. The eCFs in the filtered treatment were negatively correlated with the initial chlorophyll a concentration, picocyanobacterial abundance (mostly Prochlorococcus), and the percentage of heterotrophic prokaryotes with high nucleic acid content (%HNA). The latter two variables explained 80% of the eCF variability in the F treatment, supporting the view that both Prochlorococcus and HNA prokaryotes incorporate leucine in substantial amounts, although this results in relatively low carbon production rates in the oligotrophic ocean.
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Huete-Stauffer TM, Arandia-Gorostidi N, Díaz-Pérez L, Morán XAG. Temperature dependences of growth rates and carrying capacities of marine bacteria depart from metabolic theoretical predictions. FEMS Microbiol Ecol 2015; 91:fiv111. [PMID: 26362925 DOI: 10.1093/femsec/fiv111] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2015] [Indexed: 12/25/2022] Open
Abstract
Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6ºC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μ at the exponential phase of growth was summarized by the activation energy (E), which was variable (-0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 10(6) cells mL(-1) and generally covaried with μ but, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of live cells, the responses of μ and K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site.
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Affiliation(s)
| | - Nestor Arandia-Gorostidi
- Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía, 33212 Gijón/Xixón, Asturias, Spain
| | - Laura Díaz-Pérez
- Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía, 33212 Gijón/Xixón, Asturias, Spain
| | - Xosé Anxelu G Morán
- Centro Oceanográfico de Gijón/Xixón, Instituto Español de Oceanografía, 33212 Gijón/Xixón, Asturias, Spain Red Sea Research Center, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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12
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Våge S, Storesund JE, Thingstad TF. Adding a cost of resistance description extends the ability of virus-host model to explain observed patterns in structure and function of pelagic microbial communities. Environ Microbiol 2013; 15:1842-52. [PMID: 23331773 DOI: 10.1111/1462-2920.12077] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 12/19/2012] [Indexed: 01/21/2023]
Abstract
By adding a generic description of cost of resistance (COR) to the existing 'killing-the-winner' model, we show how this expands the model's explanatory power to include rank-abundance relationships in the host population. The model can predict a counter-intuitive relationship previously suggested in the literature, where abundant viruses are associated with rare hosts and vice versa. The model explains the observed dominance of slow-growing prokaryotes as the result of successful defence strategies, rather than as dormancy of hosts lacking essential substrates. In addition to these important conceptual aspects, the model is able to reproduce realistic values for virus : host ratios and partitioning of bacterial production between predatory loss and viral lysis. A high COR is also shown to increase the community's richness and Shannon diversity index. This model thus not only couples life strategies at the cellular level with system properties, but it also links the two system level properties of biogeochemical flows and diversity to each other. The model operates with host groups, and consequences for biodiversity when interpreting these groups in terms of species and strains are discussed.
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Affiliation(s)
- Selina Våge
- Department of Biology, University of Bergen, Bergen, Norway.
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