1
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Elsmore K, Nickols KJ, Miller LP, Ford T, Denny MW, Gaylord B. Wave damping by giant kelp, Macrocystis pyrifera. Ann Bot 2024; 133:29-40. [PMID: 37463436 PMCID: PMC11087658 DOI: 10.1093/aob/mcad094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 07/13/2023] [Indexed: 07/20/2023]
Abstract
BACKGROUND AND AIMS The increased likelihood and severity of storm events has brought into focus the role of coastal ecosystems in provision of shoreline protection by attenuating wave energy. Canopy-forming kelps, including giant kelp (Macrocystis pyrifera), are thought to provide this ecosystem service, but supporting data are extremely limited. Previous in situ examinations relied mostly on comparisons between nominally similar sites with and without kelp. Given that other factors (especially seafloor bathymetry and topographic features) often differ across sites, efforts to isolate the effects of kelp on wave energy propagation confront challenges. In particular, it can be difficult to distinguish wave energy dissipation attributable to kelp from frictional processes at the seabed that often covary with the presence of kelp. Here, we use an ecological transition from no kelp to a full forest, at a single site with static bathymetry, to resolve unambiguously the capacity of giant kelp to damp waves. METHODS We measured waves within and outside rocky reef habitat, in both the absence and the presence of giant kelp, at Marguerite Reef, Palos Verdes, CA, USA. Nested within a broader kelp restoration project, this site transitioned from a bare state to one supporting a fully formed forest (density of 8 stipes m-2). We quantified, as a function of incident wave conditions, the decline in wave energy flux attributable to the presence of kelp, as waves propagated from outside and into reef habitat. KEY RESULTS The kelp forest damped wave energy detectably, but to a modest extent. Interactions with the seabed alone reduced wave energy flux, on average, by 12 ± 1.4 % over 180 m of travel. The kelp forest induced an additional 7 ± 1.2 % decrease. Kelp-associated declines in wave energy flux were slightly greater for waves of longer periods and smaller wave heights. CONCLUSIONS Macrocystis pyrifera forests have a limited, albeit measurable, capacity to enhance shoreline protection from nearshore waves. Expectations that giant kelp forests, whether extant or enhanced through restoration, have substantial impacts on wave-induced coastal erosion might require re-evaluation.
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Affiliation(s)
- Kristen Elsmore
- Bodega Marine Laboratory, University of California at Davis, 2099 Westshore Road, Bodega Bay, CA 94923, USA
| | - Kerry J Nickols
- Department of Biology, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA
| | - Luke P Miller
- Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA
| | - Tom Ford
- Coastal Research Institute, Loyola Marymount University, 1 Loyola Marymount Drive, Los Angeles, CA 90045, USA
| | - Mark W Denny
- Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA
| | - Brian Gaylord
- Bodega Marine Laboratory, University of California at Davis, 2099 Westshore Road, Bodega Bay, CA 94923, USA
- Department of Evolution and Ecology, University of California at Davis, 1 Shields Avenue, Davis, CA 95616, USA
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2
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Crane RL, Denny MW. A bendable biological ceramic. Science 2023; 380:1216-1218. [PMID: 37347865 DOI: 10.1126/science.adi5939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/24/2023]
Abstract
A fatigue-resistant mollusk hinge could in spire the development of new materials.
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3
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Crane RL, Denny MW. Bivalves maintain repair when faced with chronically repeated mechanical stress. J Exp Biol 2022; 225:275548. [PMID: 35638557 DOI: 10.1242/jeb.243813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 04/29/2022] [Indexed: 11/20/2022]
Abstract
Even though mollusks' capacity to repair shell damage is usually studied in response to a single event, their shells have to defend them against predatory and environmental threats throughout their potentially multi-decadal life. We measured whether and how mollusks respond to chronic mechanical stress. Once a week for 7 months, we compressed whole live California mussels (Mytilus californianus) for 15 cycles at ∼55% of their predicted one-time breaking force, a treatment known to cause fatigue damage in shells. We found mussels repaired their shells. Shells of experimentally stressed mussels were just as strong at the end of the experiment as those of control mussels that had not been experimentally loaded, and they were more heavily patched internally. Additionally, stressed shells differed in morphology; they were heavier and thicker at the end of the experiment than control shells but they had increased less in width, resulting in a flatter, less domed shape. Finally, the chronic mechanical stress and repair came at a cost, with stressed mussels having higher mortality and less soft tissue than the control group. Although associated with significant cost, mussels' ability to maintain repair in response to ongoing mechanical stress may be vital to their survival in harsh and predator-filled environments.
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Affiliation(s)
- R L Crane
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - M W Denny
- Department of Biology, Stanford University, Stanford, CA 94305, USA
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4
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Moyen NE, Somero GN, Denny MW. Effects of heat acclimation on cardiac function in the intertidal mussel Mytilus californianus: can laboratory-based indices predict survival in the field? J Exp Biol 2022; 225:275332. [PMID: 35388895 PMCID: PMC9163446 DOI: 10.1242/jeb.243050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 03/22/2022] [Indexed: 12/30/2022]
Abstract
Thermal performance curves are commonly used to investigate the effects of heat acclimation on thermal tolerance and physiological performance. However, recent work indicates that the metrics of these curves heavily depend on experimental design and may be poor predictors of animal survival during heat events in the field. In intertidal mussels, cardiac thermal performance (CTP) tests have been widely used as indicators of animals' acclimation or acclimatization state, providing two indices of thermal responses: critical temperature (Tcrit; the temperature above which heart rate abruptly declines) and flatline temperature (Tflat; the temperature where heart rate ceases). Despite the wide use of CTP tests, it remains largely unknown how Tcrit and Tflat change within a single individual after heat acclimation, and whether changes in these indices can predict altered survival in the field. Here, we addressed these issues by evaluating changes in CTP indices in the same individuals before and after heat acclimation. For control mussels, merely reaching Tcrit was not lethal, whereas remaining at Tcrit for ≥10 min was lethal. Heat acclimation significantly increased Tcrit only in mussels with an initially low Tcrit (<35°C), but improved their survival time above Tcrit by 20 min on average. Tflat increased by ∼1.6°C with heat acclimation, but it is unlikely that increased Tflat improves survival in the field. In summary, Tcrit and Tflat per se may fall short of providing quantitative indices of thermal tolerance in mussels; instead, a combination of Tcrit and tolerance time at temperatures ≥Tcrit better defines changes in thermal tolerance with heat acclimation.
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5
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Burford BP, Williams RR, Demetras NJ, Carey N, Goldbogen J, Gilly WF, Harding J, Denny MW. The limits of convergence in the collective behavior of competing marine taxa. Ecol Evol 2022; 12:e8747. [PMID: 35356556 PMCID: PMC8939367 DOI: 10.1002/ece3.8747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 01/31/2022] [Accepted: 02/24/2022] [Indexed: 11/23/2022] Open
Abstract
Collective behaviors in biological systems such as coordinated movements have important ecological and evolutionary consequences. While many studies examine within‐species variation in collective behavior, explicit comparisons between functionally similar species from different taxonomic groups are rare. Therefore, a fundamental question remains: how do collective behaviors compare between taxa with morphological and physiological convergence, and how might this relate to functional ecology and niche partitioning? We examined the collective motion of two ecologically similar species from unrelated clades that have competed for pelagic predatory niches for over 500 million years—California market squid, Doryteuthis opalescens (Mollusca) and Pacific sardine, Sardinops sagax (Chordata). We (1) found similarities in how groups of individuals from each species collectively aligned, measured by angular deviation, the difference between individual orientation and average group heading. We also (2) show that conspecific attraction, which we approximated using nearest neighbor distance, was greater in sardine than squid. Finally, we (3) found that individuals of each species explicitly matched the orientation of groupmates, but that these matching responses were less rapid in squid than sardine. Based on these results, we hypothesize that information sharing is a comparably important function of social grouping for both taxa. On the other hand, some capabilities, including hydrodynamically conferred energy savings and defense against predators, could stem from taxon‐specific biology.
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Affiliation(s)
- Benjamin P. Burford
- Hopkins Marine Station of Stanford University Pacific Grove California USA
- Institute of Marine Sciences, affiliated with the National Oceanic and Atmospheric Administration National Marine Fisheries Service Southwest Fisheries Science Center University of California Santa Cruz Santa Cruz California USA
| | | | - Nicholas J. Demetras
- Institute of Marine Sciences, affiliated with the National Oceanic and Atmospheric Administration National Marine Fisheries Service Southwest Fisheries Science Center University of California Santa Cruz Santa Cruz California USA
| | - Nicholas Carey
- Hopkins Marine Station of Stanford University Pacific Grove California USA
- Marine Scotland Science Aberdeen UK
| | - Jeremy Goldbogen
- Hopkins Marine Station of Stanford University Pacific Grove California USA
| | - William F. Gilly
- Hopkins Marine Station of Stanford University Pacific Grove California USA
| | - Jeffrey Harding
- National Oceanic and Atmospheric Administration National Marine Fisheries Service Southwest Fisheries Science Center Santa Cruz California USA
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University Pacific Grove California USA
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6
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Abstract
To better understand life in the sea, marine scientists must first quantify how individual organisms experience their environment, and then describe how organismal performance depends on that experience. In this review, we first explore marine environmental variation from the perspective of pelagic organisms, the most abundant life forms in the ocean. Generation time, the ability to move relative to the surrounding water (even slowly), and the presence of environmental gradients at all spatial scales play dominant roles in determining the variation experienced by individuals, but this variation remains difficult to quantify. We then use this insight to critically examine current understanding of the environmental physiology of pelagic marine organisms. Physiologists have begun to grapple with the complexity presented by environmental variation, and promising frameworks exist for predicting and/or interpreting the consequences for physiological performance. However, new technology needs to be developed and much difficult empirical work remains, especially in quantifying response times to environmental variation and the interactions among multiple covarying factors. We call on the field of global-change biology to undertake these important challenges.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, USA;
| | - W Wesley Dowd
- School of Biological Sciences, Washington State University, Pullman, Washington 99164, USA;
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7
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Denny MW, Dowd WW. Elevated Salinity Rapidly Confers Cross-Tolerance to High Temperature in a Splash-Pool Copepod. Integr Org Biol 2022; 4:obac037. [PMID: 36003414 PMCID: PMC9394168 DOI: 10.1093/iob/obac037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/07/2022] [Accepted: 08/04/2022] [Indexed: 12/11/2022] Open
Abstract
Accurate forecasting of organismal responses to climate change requires a deep mechanistic understanding of how physiology responds to present-day variation in the physical environment. However, the road to physiological enlightenment is fraught with complications: predictable environmental fluctuations of any single factor are often accompanied by substantial stochastic variation and rare extreme events, and several factors may interact to affect physiology. Lacking sufficient knowledge of temporal patterns of co-variation in multiple environmental stressors, biologists struggle to design and implement realistic and relevant laboratory experiments. In this study, we directly address these issues, using measurements of the thermal tolerance of freshly collected animals and long-term field records of environmental conditions to explore how the splash-pool copepod Tigriopus californicus adjusts its physiology as its environment changes. Salinity and daily maximum temperature-two dominant environmental stressors experienced by T. californicus-are extraordinarily variable and unpredictable more than 2-3 days in advance. However, they substantially co-vary such that when temperature is high salinity is also likely to be high. Copepods appear to take advantage of this correlation: median lethal temperature of field-collected copepods increases by 7.5°C over a roughly 120 parts-per-thousand range of ambient salinity. Complementary laboratory experiments show that exposure to a single sublethal thermal event or to an abrupt shift in salinity also elicits rapid augmentation of heat tolerance via physiological plasticity, although the effect of salinity dwarfs that of temperature. These results suggest that T. californicus's physiology keeps pace with the rapid, unpredictable fluctuations of its hypervariable physical environment by responding to the cues provided by recent sublethal stress and, more importantly, by leveraging the mechanistic cross-talk between responses to salinity and heat stress.
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Affiliation(s)
| | - W Wesley Dowd
- School of Biological Sciences, Washington State University, 100 Dairy Road, Eastlick G81, Pullman, WA99164, USA
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8
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Burford B, Wild LA, Schwarz R, Chenoweth EM, Sreenivasan A, Elahi R, Carey N, Hoving HJT, Straley JM, Denny MW. Rapid range expansion of a marine ectotherm reveals the demographic and ecological consequences of short-term variability in seawater temperature and dissolved oxygen. Am Nat 2021; 199:523-550. [DOI: 10.1086/718575] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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9
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Crane RL, Diaz Reyes JL, Denny MW. Bivalves rapidly repair shells damaged by fatigue and bolster strength. J Exp Biol 2021; 224:272465. [PMID: 34648024 PMCID: PMC8541735 DOI: 10.1242/jeb.242681] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 09/05/2021] [Indexed: 12/03/2022]
Abstract
Hard external armors have to defend against a lifetime of threats yet are traditionally understood by their ability to withstand a single attack. Survival of bivalve mollusks thus can depend on the ability to repair shell damage between encounters. We studied the capacity for repair in the intertidal mussel Mytilus californianus by compressing live mussels for 15 cycles at ∼79% of their predicted strength (critically fracturing 46% of shells), then allowing the survivors 0, 1, 2 or 4 weeks to repair. Immediately after fatigue loading, mussel shells were 20% weaker than control shells that had not experienced repetitive loading. However, mussels restored full shell strength within 1 week, and after 4 weeks shells that had experienced greater fatiguing forces were stronger than those repetitively loaded at lower forces. Microscopy supported the hypothesis that crack propagation is a mechanism of fatigue-caused weakening. However, the mechanism of repair was only partially explained, as epifluorescence microscopy of calcein staining for shell deposition showed that only half of the mussels that experienced repetitive loading had initiated direct repair via shell growth around fractures. Our findings document repair weeks to months faster than demonstrated in other mollusks. This rapid repair may be important for the mussels’ success contending with predatory and environmental threats in the harsh environment of wave-swept rocky coasts, allowing them to address non-critical but weakening damage and to initiate plastic changes to shell strength. We highlight the significant insight gained by studying biological armors not as static structures but, instead, as dynamic systems that accumulate, repair and respond to damage. Highlighted Article: Mussels repair shell damage caused by fatigue within one week and further strengthen shells within one month. Bivalve shells are a dynamic armor, responsive to accumulating weakening damage.
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Affiliation(s)
- R L Crane
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - J L Diaz Reyes
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - M W Denny
- Department of Biology, Stanford University, Stanford, CA 94305, USA
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10
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Moyen NE, Crane RL, Somero GN, Denny MW. A single heat-stress bout induces rapid and prolonged heat acclimation in the California mussel, Mytilus californianus. Proc Biol Sci 2020; 287:20202561. [PMID: 33290677 DOI: 10.1098/rspb.2020.2561] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Climate change is not only causing steady increases in average global temperatures but also increasing the frequency with which extreme heating events occur. These extreme events may be pivotal in determining the ability of organisms to persist in their current habitats. Thus, it is important to understand how quickly an organism's heat tolerance can be gained and lost relative to the frequency with which extreme heating events occur in the field. We show that the California mussel, Mytilus californianus-a sessile intertidal species that experiences extreme temperature fluctuations and cannot behaviourally thermoregulate-can quickly (in 24-48 h) acquire improved heat tolerance after exposure to a single sublethal heat-stress bout (2 h at 30 or 35°C) and then maintain this improved tolerance for up to three weeks without further exposure to elevated temperatures. This adaptive response improved survival rates by approximately 75% under extreme heat-stress bouts (2 h at 40°C). To interpret these laboratory findings in an ecological context, we evaluated 4 years of mussel body temperatures recorded in the field. The majority (approx. 64%) of consecutive heat-stress bouts were separated by 24-48 h, but several consecutive heat bouts were separated by as much as 22 days. Thus, the ability of M. californianus to maintain improved heat tolerance for up to three weeks after a single sublethal heat-stress bout significantly improves their probability of survival, as approximately 33% of consecutive heat events are separated by 3-22 days. As a sessile animal, mussels likely evolved the capability to rapidly gain and slowly lose heat tolerance to survive the intermittent, and often unpredictable, heat events in the intertidal zone. This adaptive strategy will likely prove beneficial under the extreme heat events predicted with climate change.
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Affiliation(s)
- Nicole E Moyen
- Hopkins Marine Station, Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Rachel L Crane
- Hopkins Marine Station, Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - George N Somero
- Hopkins Marine Station, Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Mark W Denny
- Hopkins Marine Station, Department of Biology, Stanford University, Stanford, CA 94305, USA
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11
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Affiliation(s)
- Diana E. LaScala‐Gruenewald
- Dept of Biology, Stanford Univ. Stanford CA 94305 USA
- Monterey Bay Aquarium Res. Inst. Moss Landing CA 95039 USA
| | - Mark W. Denny
- Dept of Biology, Stanford Univ. Stanford CA 94305 USA
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12
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Moyen NE, Somero GN, Denny MW. Mussel acclimatization to high, variable temperatures is lost slowly upon transfer to benign conditions. J Exp Biol 2020; 223:jeb222893. [PMID: 32457061 DOI: 10.1242/jeb.222893] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 05/18/2020] [Indexed: 12/18/2022]
Abstract
Climate change is increasing the temperature variability animals face, and thermal acclimatization allows animals to adjust adaptively to this variability. Although the rate of heat acclimatization has received some study, little is known about how long these adaptive changes remain without continuing exposure to heat stress. This study explored the rate at which field acclimatization states are lost when temperature variability is minimized during constant submersion. California mussels (Mytilus californianus) with different acclimatization states were collected from high- and low-zone sites (∼12 versus ∼5°C daily temperature ranges, respectively) and then kept submerged at 15°C for 8 weeks. Each week, the cardiac thermal performance of mussels was measured as a metric of acclimatization state: critical (Tcrit) and flatline (Tflat) temperatures were recorded. Over 8 weeks of constant submersion, the mean Tcrit of high-zone mussels decreased by 1.07°C from baseline, but low-zone mussels' mean Tcrit was unchanged. High- and low-zone mussels' mean maximum heart rate (HR) and resting HR decreased ∼12 and 35%, respectively. Tflat was unchanged in both groups. These data suggest that Tcrit and HR are more physiologically plastic in response to the narrowing of an animal's daily temperature range than Tflat is, and that an animal's prior acclimatization state (high versus low) influences the acclimatory capacity of Tcrit Approximately 2 months were required for the cardiac thermal performance of the high-zone mussels to reach that of the low-zone mussels, suggesting that acclimatization to high and variable temperatures may persist long enough to enable these animals to cope with intermittent bouts of heat stress.
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Affiliation(s)
- Nicole E Moyen
- Hopkins Marine Station, Department of Biology, Stanford University, Pacific Grove, CA 94305, USA
| | - George N Somero
- Hopkins Marine Station, Department of Biology, Stanford University, Pacific Grove, CA 94305, USA
| | - Mark W Denny
- Hopkins Marine Station, Department of Biology, Stanford University, Pacific Grove, CA 94305, USA
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13
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Abstract
Mollusk shells protect against diverse environmental and predatory physical threats, from one-time impacts to chronic, low-magnitude stresses. The effectiveness of shells as armor is often quantified with a test of shell strength: increasing force is applied until catastrophic fracture. This test does not capture the potential role of fatigue, a process by which chronic or repeated, low-magnitude forces weaken and break a structure. We quantified the strength and fatigue resistance of California mussel (Mytilus californianus) shells. Shells were fatigue tested until catastrophic failure by either loading a valve repeatedly to a set force (cyclic) or loading a valve under constant force (static). Valves fatigued under both cyclic and static loading, i.e. subcritical forces broke valves when applied repeatedly or for long durations. Stronger and more fatigue-resistant valves tended to be more massive, relatively wider and the right-hand valve. Furthermore, after accounting for the valves' predicted strength, fatigue resistance curves for cyclic and static loading did not differ, suggesting that fatigue fracture of mussels is more dependent on force duration than number of cycles. Contextualizing fatigue resistance with the forces mussels typically experience clarifies the range of threats for which fatigue becomes relevant. Some predators could rely on fatigue, and episodic events like large wave impacts or failed predation attempts could weaken shells across long time scales. Quantifying shell fatigue resistance when considering the ecology of shelled organisms or the evolution of shell form offers a perspective that accounts for the accumulating damage of a lifetime of threats, large and small.
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Affiliation(s)
- R L Crane
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
| | - M W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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14
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Moyen NE, Bump PA, Somero GN, Denny MW. Establishing typical values for hemocyte mortality in individual California mussels, Mytilus californianus. Fish Shellfish Immunol 2020; 100:70-79. [PMID: 32135339 DOI: 10.1016/j.fsi.2020.02.069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 02/24/2020] [Accepted: 02/29/2020] [Indexed: 06/10/2023]
Abstract
Hemocytes are immune cells in the hemolymph of invertebrates that play multiple roles in response to stressors; hemocyte mortality can thus serve as an indicator of overall animal health. However, previous research has often analyzed hemolymph samples pooled from several individuals, which precludes tracking individual responses to stressors over time. The ability to track individuals is important, however, because large inter-individual variation in response to stressors can confound the interpretation of pooled samples. Here, we describe protocols for analysis of inter- and intra-individual variability in hemocyte mortality across repeated hemolymph samples of California mussels, Mytilus californianus, free from typical abiotic stressors. To assess individual variability in hemocyte mortality with serial sampling, we created four groups of 15 mussels each that were repeatedly sampled four times: at baseline (time zero) and three subsequent times separated by either 24, 48, 72, or 168 h. Hemocyte mortality was assessed by fluorescence-activated cell sorting (FACS) of cells stained with propidium iodide. Our study demonstrates that hemolymph can be repeatedly sampled from individual mussels without mortality; however, there is substantial inter- and intra-individual variability in hemocyte mortality through time that is partially dependent on the sampling interval. Across repeated samples, individual mussels' hemocyte mortality had, on average, a range of ~6% and a standard deviation of ~3%, which was minimized with sampling periods ≥72 h apart. Due to this intra-individual variability, obtaining ≥2 samples from a specimen will more accurately establish an individual's baseline. Pooled-sample means were similar to individual-sample means; however, pooled samples masked the individual variation in each group. Overall, these data lay the foundation for future work exploring individual mussels' temporal responses to various stressors on a cellular level.
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Affiliation(s)
- Nicole E Moyen
- Hopkins Marine Station, Department of Biology, Stanford University, United States.
| | - Paul A Bump
- Hopkins Marine Station, Department of Biology, Stanford University, United States
| | - George N Somero
- Hopkins Marine Station, Department of Biology, Stanford University, United States
| | - Mark W Denny
- Hopkins Marine Station, Department of Biology, Stanford University, United States
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15
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Moyen NE, Bump PA, Somero GN, Denny MW. Establishing typical values for hemocyte mortality in individual mussels (
Mytilus californianus
) using fluorescence‐activated cell sorting. FASEB J 2020. [DOI: 10.1096/fasebj.2020.34.s1.01786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Dowd WW, Denny MW. A series of unfortunate events: characterizing the contingent nature of physiological extremes using long-term environmental records. Proc Biol Sci 2020; 287:20192333. [PMID: 31937220 PMCID: PMC7003452 DOI: 10.1098/rspb.2019.2333] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 12/09/2019] [Indexed: 11/12/2022] Open
Abstract
Accelerating shifts in global climate have focused the attention of ecologists and physiologists on extreme environmental events. However, the dynamic process of physiological acclimatization complicates study of these events' consequences. Depending on the range of plasticity and the amplitude and speed of environmental variation, physiology can be either in tune with the surroundings or dangerously out of synch. We implement a modified quantitative approach to identifying extreme events in environmental records, proposing that organisms are stressed by deviations of the environment from the current level of acclimatization, rather than by the environment's absolute state. This approach facilitates an unambiguous null model for the consequences of environmental variation, identifying a unique subset of events as 'extremes'. Specifically, it allows one to examine how both the temporal extent (the acclimatization window) and type of an environmental signal affect the magnitude and timing of extreme environmental events. For example, if physiology responds to the moving average of past conditions, a longer acclimatization window generally results in greater imposed stress. If instead physiology responds to historical maxima, longer acclimatization windows reduce imposed stress, albeit perhaps at greater constitutive cost. This approach should be further informed and tested with empirical experiments addressing the history-dependent nature of acclimatization.
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Affiliation(s)
- W. Wesley Dowd
- School of Biological Sciences, Washington State University, Pullman, WA 99164, USA
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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17
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LaScala-Gruenewald DE, Mehta RS, Liu Y, Denny MW. Sensory perception plays a larger role in foraging efficiency than heavy-tailed movement strategies. Ecol Modell 2019. [DOI: 10.1016/j.ecolmodel.2019.02.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Moyen NE, Somero GN, Denny MW. Impact of heating rate on cardiac thermal tolerance in the California mussel, Mytilus californianus. J Exp Biol 2019; 222:jeb.203166. [DOI: 10.1242/jeb.203166] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 08/01/2019] [Indexed: 01/06/2023]
Abstract
Intertidal communities of wave-swept rocky shores have served as a powerful model system for experiments in ecology, and mussels (the dominant competitor for space in the mid-intertidal zone) play a central role in determining community structure in this physically stressful habitat. Consequently, our ability to account for mussels’ physiological responses to thermal stress affects ecologists’ abilities to predict the impacts of a warming climate on this ecosystem. Here, we examine the effect of heating rate on cardiac thermal tolerance in the ribbed mussel, Mytilus californianus, comparing populations from high and low sites in the intertidal zone where emersion duration leads to different mean daily heating rates. Two temperature-related cardiac variables were examined: 1) the critical temperature (Hcrit) at which heart rate (HR) precipitously declines, and 2) flatline temperature (FLT) where HR reaches zero. Mussels were heated in air at slow, moderate, and fast rates, and heart rate was measured via an infrared sensor affixed to the shell. Faster heating rates significantly increased Hcrit in high-, but not low-zone mussels, and Hcrit was higher in high vs. - mussels, especially at the fastest heating rate. By contrast, FLT did not differ between zones, and was minimally affected by heating rate. Since heating rate significantly impacted high- but not low-zone mussels’ cardiac thermal tolerance, realistic zone-specific heating rates must be used in laboratory tests if those tests are to provide accurate information for ecological models attempting to predict the effects of increasing temperature on intertidal communities.
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Affiliation(s)
- Nicole E. Moyen
- Hopkins Marine Station, Department of Biology, Stanford University, USA
| | - George N. Somero
- Hopkins Marine Station, Department of Biology, Stanford University, USA
| | - Mark W. Denny
- Hopkins Marine Station, Department of Biology, Stanford University, USA
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Denny MW, King FA. The extraordinary joint material of an articulated coralline alga. II. Modeling the structural basis of its mechanical properties. ACTA ACUST UNITED AC 2017; 219:1843-50. [PMID: 27307542 DOI: 10.1242/jeb.138867] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 03/29/2016] [Indexed: 11/20/2022]
Abstract
By incorporating joints into their otherwise rigid fronds, erect coralline algae have evolved to be as flexible as other seaweeds, which allows them to thrive - and even dominate space - on wave-washed shores around the globe. However, to provide the required flexibility, the joint tissue of Calliarthron cheilosporioides, a representative articulated coralline alga, relies on an extraordinary tissue that is stronger, more extensible and more fatigue resistant than that of other algae. Here, we used the results from recent experiments to parameterize a conceptual model that links the microscale architecture of cell walls to the adaptive mechanical properties of joint tissue. Our analysis suggests that the theory of discontinuous fiber-wound composite materials (with cellulose fibrils as the fibers and galactan gel as the matrix) can explain key aspects of the material's mechanics. In particular, its adaptive viscoelastic behavior can be characterized by two, widely separated time constants. We speculate that the short time constant (∼14 s) results from the viscous response of the matrix to the change in cell-wall shape as a joint is stretched, a response that allows the material both to remain flexible and to dissipate energy as a frond is lashed by waves. We propose that the long time constant (∼35 h), is governed by the shearing of the matrix between cellulose fibrils. The resulting high apparent viscosity ensures that joints avoid accumulating lethal deformation in the course of a frond's lifetime. Our synthesis of experimental measurements allows us to draw a chain of mechanistic inference from molecules to cell walls to fronds and community ecology.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
| | - Felicia A King
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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20
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Denny MW, King FA. The extraordinary joint material of an articulated coralline alga. I. Mechanical characterization of a key adaptation. ACTA ACUST UNITED AC 2017; 219:1833-42. [PMID: 27307541 DOI: 10.1242/jeb.138859] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 03/29/2016] [Indexed: 11/20/2022]
Abstract
Flexibility is key to survival for seaweeds exposed to the extreme hydrodynamic environment of wave-washed rocky shores. This poses a problem for coralline algae, whose calcified cell walls make them rigid. Through the course of evolution, erect coralline algae have solved this problem by incorporating joints (genicula) into their morphology, allowing their fronds to be as flexible as those of uncalcified seaweeds. To provide the flexibility required by this structural innovation, the joint material of Calliarthron cheilosporioides, a representative articulated coralline alga, relies on an extraordinary tissue that is stronger, more extensible and more fatigue resistant than the tissue of other algal fronds. Here, we report on experiments that reveal the viscoelastic properties of this material. On the one hand, its compliance is independent of the rate of deformation across a wide range of deformation rates, a characteristic of elastic solids. This deformation rate independence allows joints to maintain their flexibility when loaded by the unpredictable - and often rapidly imposed - hydrodynamic force of breaking waves. On the other hand, the genicular material has viscous characteristics that similarly augment its function. The genicular material dissipates much of the energy absorbed as a joint is deformed during cyclic wave loading, which potentially reduces the chance of failure by fatigue, and the material accrues a limited amount of deformation through time. This limited creep increases the flexibility of the joints while preventing them from gradually stretching to the point of failure. These new findings provide the basis for understanding how the microscale architecture of genicular cell walls results in the adaptive mechanical properties of coralline algal joints.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
| | - Felicia A King
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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21
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Shadwick RE, Denny MW. John Moffit Gosline, BA, PhD, FRSC (1943–2016). J Exp Biol 2017; 220:334-335. [DOI: 10.1242/jeb.155960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Robert E. Shadwick
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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22
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Helmuth B, Choi F, Matzelle A, Torossian JL, Morello SL, Mislan KAS, Yamane L, Strickland D, Szathmary PL, Gilman SE, Tockstein A, Hilbish TJ, Burrows MT, Power AM, Gosling E, Mieszkowska N, Harley CDG, Nishizaki M, Carrington E, Menge B, Petes L, Foley MM, Johnson A, Poole M, Noble MM, Richmond EL, Robart M, Robinson J, Sapp J, Sones J, Broitman BR, Denny MW, Mach KJ, Miller LP, O'Donnell M, Ross P, Hofmann GE, Zippay M, Blanchette C, Macfarlan JA, Carpizo-Ituarte E, Ruttenberg B, Peña Mejía CE, McQuaid CD, Lathlean J, Monaco CJ, Nicastro KR, Zardi G. Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors. Sci Data 2016; 3:160087. [PMID: 27727238 PMCID: PMC5058338 DOI: 10.1038/sdata.2016.87] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 08/30/2016] [Indexed: 11/12/2022] Open
Abstract
At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10–30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0–2.5 °C, during daily fluctuations that often exceeded 15°–20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature.
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Affiliation(s)
- Brian Helmuth
- Northeastern University, Marine Science Center, 430 Nahant Rd., Nahant, Massachusetts 01908, USA
| | - Francis Choi
- Northeastern University, Marine Science Center, 430 Nahant Rd., Nahant, Massachusetts 01908, USA
| | - Allison Matzelle
- Northeastern University, Marine Science Center, 430 Nahant Rd., Nahant, Massachusetts 01908, USA
| | - Jessica L Torossian
- Northeastern University, Marine Science Center, 430 Nahant Rd., Nahant, Massachusetts 01908, USA
| | | | - K A S Mislan
- University of Washington, School of Oceanography, Seattle, Washington 98195, USA
| | - Lauren Yamane
- University of California, Davis, Department of Wildlife, Fish, and Conservation Biology, Davis, California 95616, USA
| | - Denise Strickland
- University of South Carolina, Department of Biological Sciences, Columbia, South Carolina 29208, USA
| | - P Lauren Szathmary
- University of South Carolina, Department of Biological Sciences, Columbia, South Carolina 29208, USA
| | - Sarah E Gilman
- W.M. Keck Science Department of Claremont McKenna, Pitzer and Scripps Colleges, Claremont, California 91711, USA
| | - Alyson Tockstein
- University of South Carolina, Department of Biological Sciences, Columbia, South Carolina 29208, USA
| | - Thomas J Hilbish
- University of South Carolina, Department of Biological Sciences, Columbia, South Carolina 29208, USA
| | - Michael T Burrows
- Scottish Association for Marine Science, Oban, Argyll PA37 1QA, Scotland
| | - Anne Marie Power
- Anne Marie Power, School of Natural Sciences, National University of Ireland Galway, Galway H91 TK33, Ireland
| | - Elizabeth Gosling
- School of Life Sciences, Galway-Mayo Institute of Technology, Galway H91 T8NW, Ireland
| | - Nova Mieszkowska
- Marine Biological Association of the United Kingdom, Plymouth, Devon PL1 2PB, UK
| | - Christopher D G Harley
- University of British Columbia, Department of Zoology and Biodiversity Research Centre, Vancouver, British Columbia, Canada V6T1Z4
| | - Michael Nishizaki
- University of Washington, Department of Biology, Seattle, Washington 98195, USA
| | - Emily Carrington
- University of Washington, Department of Biology, Seattle, Washington 98195, USA
| | - Bruce Menge
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Laura Petes
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Melissa M Foley
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Angela Johnson
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Megan Poole
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Mae M Noble
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Erin L Richmond
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Matt Robart
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Jonathan Robinson
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Jerod Sapp
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon 97331, USA
| | - Jackie Sones
- University of California, Davis, Bodega Marine Reserve, Bodega Bay, California 94923, USA
| | | | - Mark W Denny
- Stanford University, Hopkins Marine Station, Pacific Grove, California 93950, USA
| | - Katharine J Mach
- Stanford University, Hopkins Marine Station, Pacific Grove, California 93950, USA
| | - Luke P Miller
- Stanford University, Hopkins Marine Station, Pacific Grove, California 93950, USA
| | - Michael O'Donnell
- Stanford University, Hopkins Marine Station, Pacific Grove, California 93950, USA
| | - Philip Ross
- University of Waikato, Environmental Research Institute, Tauranga 3110, New Zealand
| | - Gretchen E Hofmann
- University of California Santa Barbara, Marine Science Institute, Santa Barbara, California 93106, USA
| | - Mackenzie Zippay
- University of California Santa Barbara, Marine Science Institute, Santa Barbara, California 93106, USA
| | - Carol Blanchette
- University of California Santa Barbara, Marine Science Institute, Santa Barbara, California 93106, USA
| | - J A Macfarlan
- University of California Santa Barbara, Marine Science Institute, Santa Barbara, California 93106, USA
| | - Eugenio Carpizo-Ituarte
- Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas, Ensenada, Baja California 22860, Mexico
| | - Benjamin Ruttenberg
- Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas, Ensenada, Baja California 22860, Mexico
| | - Carlos E Peña Mejía
- Universidad Autónoma de Baja California, Instituto de Investigaciones Oceanológicas, Ensenada, Baja California 22860, Mexico
| | - Christopher D McQuaid
- Rhodes University, Department of Zoology and Entomology, Grahamstown 6140, South Africa
| | - Justin Lathlean
- Rhodes University, Department of Zoology and Entomology, Grahamstown 6140, South Africa
| | - Cristián J Monaco
- Rhodes University, Department of Zoology and Entomology, Grahamstown 6140, South Africa
| | - Katy R Nicastro
- Rhodes University, Department of Zoology and Entomology, Grahamstown 6140, South Africa
| | - Gerardo Zardi
- Rhodes University, Department of Zoology and Entomology, Grahamstown 6140, South Africa
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23
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Abstract
ABSTRACT
In this review we consider how small-scale temporal and spatial variation in body temperature, and biochemical/physiological variation among individuals, affect the prediction of organisms' performance in nature. For ‘normal’ body temperatures – benign temperatures near the species' mean – thermal biology traditionally uses performance curves to describe how physiological capabilities vary with temperature. However, these curves, which are typically measured under static laboratory conditions, can yield incomplete or inaccurate predictions of how organisms respond to natural patterns of temperature variation. For example, scale transition theory predicts that, in a variable environment, peak average performance is lower and occurs at a lower mean temperature than the peak of statically measured performance. We also demonstrate that temporal variation in performance is minimized near this new ‘optimal’ temperature. These factors add complexity to predictions of the consequences of climate change. We then move beyond the performance curve approach to consider the effects of rare, extreme temperatures. A statistical procedure (the environmental bootstrap) allows for long-term simulations that capture the temporal pattern of extremes (a Poisson interval distribution), which is characterized by clusters of events interspersed with long intervals of benign conditions. The bootstrap can be combined with biophysical models to incorporate temporal, spatial and physiological variation into evolutionary models of thermal tolerance. We conclude with several challenges that must be overcome to more fully develop our understanding of thermal performance in the context of a changing climate by explicitly considering different forms of small-scale variation. These challenges highlight the need to empirically and rigorously test existing theories.
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Affiliation(s)
- W. Wesley Dowd
- Loyola Marymount University, Department of Biology, Los Angeles, CA 90045, USA
| | - Felicia A. King
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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24
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Abstract
Abstract
Squid are the largest jet propellers in nature as adults, but as paralarvae they are some of the smallest, faced with the inherent inefficiency of jet propulsion at low Reynolds number. In this study we describe the behavior and kinematics of locomotion in 1 mm paralarvae of Dosidicus gigas, the smallest squid yet studied. They swim with hop-and-sink behavior and can engage in fast jets by reducing the size of the mantle aperture during the contraction phase of a jetting cycle. We go on to explore the general effects of a variable mantle and funnel aperture in a theoretical model of jet propulsion scaled from the smallest (1 mm mantle length) to the largest (3 m) squid. Aperture reduction during mantle contraction increases propulsive efficiency at all squid sizes, although 1 mm squid still suffer from low efficiency (20%) due to a limited speed of contraction. Efficiency increases to a peak of 40% for 1 cm squid, then slowly declines. Squid larger than 6 cm must either reduce contraction speed or increase aperture size to maintain stress within maximal muscle tolerance. Ecological pressure to maintain maximum velocity may lead them to increase aperture size, which reduces efficiency. This effect may be ameliorated by nonaxial flow during the refill phase of the cycle. Our model's predictions highlight areas for future empirical work, and emphasize the existence of complex behavioral options for maximizing efficiency at both very small and large sizes.
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25
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Mach KJ, Tepler SK, Staaf AV, Bohnhoff JC, Denny MW. Failure by fatigue in the field: a model of fatigue breakage for the macroalga Mazzaella, with validation. ACTA ACUST UNITED AC 2011; 214:1571-85. [PMID: 21490265 DOI: 10.1242/jeb.051623] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Seaweeds inhabiting the extreme hydrodynamic environment of wave-swept shores break frequently. However, traditional biomechanical analyses, evaluating breakage due to the largest individual waves, have perennially underestimated rates of macroalgal breakage. Recent laboratory testing has established that some seaweeds fail by fatigue, accumulating damage over a series of force impositions. Failure by fatigue may thus account, in part, for the discrepancy between prior breakage predictions, based on individual not repeated wave forces, and reality. Nonetheless, the degree to which fatigue breaks seaweeds on wave-swept shores remains unknown. Here, we developed a model of fatigue breakage due to wave-induced forces for the macroalga Mazzaella flaccida. To test model performance, we made extensive measurements of M. flaccida breakage and of wave-induced velocities experienced by the macroalga. The fatigue-breakage model accounted for significantly more breakage than traditional prediction methods. For life history phases modeled most accurately, 105% (for female gametophytes) and 79% (for tetrasporophytes) of field-observed breakage was predicted, on average. When M. flaccida fronds displayed attributes such as temperature stress and substantial tattering, the fatigue-breakage model underestimated breakage, suggesting that these attributes weaken fronds and lead to more rapid breakage. Exposure to waves had the greatest influence on model performance. At the most wave-protected sites, the model underpredicted breakage, and at the most wave-exposed sites, it overpredicted breakage. Overall, our fatigue-breakage model strongly suggests that, in addition to occurring predictably in the laboratory, fatigue-induced breakage of M. flaccida occurs on wave-swept shores.
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Affiliation(s)
- Katharine J Mach
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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26
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Abstract
For organisms living in the intertidal zone, temperature is an important selective agent that can shape species distributions and drive phenotypic variation among populations. Littorinid snails, which occupy the upper limits of rocky shores and estuaries worldwide, often experience extreme high temperatures and prolonged aerial emersion during low tides, yet their robust physiology--coupled with morphological and behavioral traits--permits these gastropods to persist and exert strong grazing control over algal communities. We use a mechanistic heat-budget model to compare the effects of behavioral and morphological traits on the body temperatures of five species of littorinid snails under natural weather conditions. Model predictions and field experiments indicate that, for all five species, the relative contribution of shell color or sculpturing to temperature regulation is small, on the order of 0.2-2 °C, while behavioral choices such as removing the foot from the substratum or reorienting the shell can lower body temperatures by 2-4 °C on average. Temperatures in central California rarely exceeded the thermal tolerance limits of the local littorinid species during the study period, but at sites where snails are regularly exposed to extreme high temperatures, the functional significance of the tested traits may be important. The mechanistic approach used here provides the ability to gauge the importance of behavioral and morphological traits for controlling body temperature as species approach their physiological thresholds.
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Affiliation(s)
- Luke P Miller
- Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, USA.
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28
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Helmuth B, Broitman BR, Yamane L, Gilman SE, Mach K, Mislan KAS, Denny MW. Organismal climatology: analyzing environmental variability at scales relevant to physiological stress. ACTA ACUST UNITED AC 2010; 213:995-1003. [PMID: 20190124 DOI: 10.1242/jeb.038463] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Predicting when, where and with what magnitude climate change is likely to affect the fitness, abundance and distribution of organisms and the functioning of ecosystems has emerged as a high priority for scientists and resource managers. However, even in cases where we have detailed knowledge of current species' range boundaries, we often do not understand what, if any, aspects of weather and climate act to set these limits. This shortcoming significantly curtails our capacity to predict potential future range shifts in response to climate change, especially since the factors that set range boundaries under those novel conditions may be different from those that set limits today. We quantitatively examine a nine-year time series of temperature records relevant to the body temperatures of intertidal mussels as measured using biomimetic sensors. Specifically, we explore how a 'climatology' of body temperatures, as opposed to long-term records of habitat-level parameters such as air and water temperatures, can be used to extrapolate meaningful spatial and temporal patterns of physiological stress. Using different metrics that correspond to various aspects of physiological stress (seasonal means, cumulative temperature and the return time of extremes) we show that these potential environmental stressors do not always occur in synchrony with one another. Our analysis also shows that patterns of animal temperature are not well correlated with simple, commonly used metrics such as air temperature. Detailed physiological studies can provide guidance to predicting the effects of global climate change on natural ecosystems but only if we concomitantly record, archive and model environmental signals at appropriate scales.
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Affiliation(s)
- Brian Helmuth
- University of South Carolina, Department of Biological Sciences, Columbia, SC 29208, USA.
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29
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Abstract
The emerging field of marine ecomechanics provides an explicit physical framework for exploring interactions among marine organisms and between these organisms and their environments. It exhibits particular utility through its construction of predictive, mechanistic models, a number of which address responses to changing climatic conditions. Examples include predictions of (a) the change in relative abundance of corals as a function of colony morphology, ocean acidity, and storm intensity; (b) the rate of disturbance and patch formation in beds of mussels, a competitive dominant on many intertidal shores; (c) the dispersal and recruitment patterns of giant kelps, an important nearshore foundation species; (d) the effects of turbulence on external fertilization, a widespread method of reproduction in the sea; and (e) the long-term incidence of extreme ecological events. These diverse examples emphasize the breadth of marine ecomechanics. Indeed, its principles can be applied to any ecological system.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, USA.
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31
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Miller LP, Harley CDG, Denny MW. The role of temperature and desiccation stress in limiting the local-scale distribution of the owl limpet,Lottia gigantea. Funct Ecol 2009. [DOI: 10.1111/j.1365-2435.2009.01567.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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33
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Abstract
SUMMARY
Are there absolute limits to the speed at which animals can run? If so, how close are present-day individuals to these limits? I approach these questions by using three statistical models and data from competitive races to estimate maximum running speeds for greyhounds, thoroughbred horses and elite human athletes. In each case, an absolute speed limit is definable, and the current record approaches that predicted maximum. While all such extrapolations must be used cautiously, these data suggest that there are limits to the ability of either natural or artificial selection to produce ever faster dogs, horses and humans. Quantification of the limits to running speed may aid in formulating and testing models of locomotion.
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Affiliation(s)
- Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,USA
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34
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Abstract
Hydrodynamic forces dislodge and kill large numbers of organisms in intertidal and subtidal habitats along rocky shores. Although this feature of wave-driven water motion is well recognized, the mechanics of force imposition on compliant organisms is incompletely understood. Here we undertake a field examination of two processes that are thought to impose many of the more dangerous forces that act on flexible benthic seaweeds: impingement of breaking waves directly on emergent organisms, and inertial effects tied to the rapid deceleration of mass that occurs when a passively moving but attached organism abruptly reaches the extent of its range of motion. We focus on two common and important seaweed species: one intertidal kelp (Egregia menziesii) and one subtidal kelp (Macrocystis pyrifera). Results support the concept that wave impingement and inertial effects produce intermittent force transients whose magnitudes commonly exceed values readily attributable to drag. Peak force transients are elevated by as much as a factor of 3 relative to drag in both small and large individuals, consistent with smaller seaweeds being more susceptible to brief impingement forces, and larger seaweeds being more vulnerable to inertial forces. Because both wave impingement and inertial effects vary with the size of an organism, they may have the potential to influence the demographics of physical disturbance in an array of flexible species.
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Affiliation(s)
- Brian Gaylord
- Bodega Marine Laboratory and Department of Evolution and Ecology, University of California at Davis, Bodega Bay, California 94923, USA.
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35
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Martone PT, Denny MW. To bend a coralline: effect of joint morphology on flexibility and stress amplification in an articulated calcified seaweed. J Exp Biol 2008; 211:3421-32. [DOI: 10.1242/jeb.020479] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYPrevious studies have demonstrated that fleshy seaweeds resist wave-induced drag forces in part by being flexible. Flexibility allows fronds to `go with the flow', reconfiguring into streamlined shapes and reducing frond area projected into flow. This paradigm extends even to articulated coralline algae, which produce calcified fronds that are flexible only because they have distinct joints (genicula). The evolution of flexibility through genicula was a major event that allowed articulated coralline algae to grow elaborate erect fronds in wave-exposed habitats. Here we describe the mechanics of genicula in the articulated coralline Calliarthron and demonstrate how segmentation affects bending performance and amplifies bending stresses within genicula. A numerical model successfully predicted deflections of articulated fronds by assuming genicula to be assemblages of cables connecting adjacent calcified segments (intergenicula). By varying the dimensions of genicula in the model, we predicted the optimal genicular morphology that maximizes flexibility while minimizing stress amplification. Morphological dimensions of genicula most prone to bending stresses (i.e. genicula near the base of fronds) match model predictions.
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Affiliation(s)
- Patrick T. Martone
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,USA
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,USA
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36
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Abstract
SUMMARY
Previous studies have hypothesized that wave-induced drag forces may constrain the size of intertidal organisms by dislodging or breaking organisms that exceed some critical dimension. In this study, we explored constraints on the size of the articulated coralline alga Calliarthron, which thrives in wave-exposed intertidal habitats. Its ability to survive depends critically upon its segmented morphology (calcified segments separated by flexible joints or `genicula'), which allows otherwise rigid fronds to bend and thereby reduce drag. However, bending also amplifies stress within genicula near the base of fronds. We quantified breakage of genicula in bending by applying known forces to fronds until they broke. Using a mathematical model, we demonstrate the mitigating effect of neighboring fronds on breakage and show that fronds growing within dense populations are no more likely to break in bending than in tension, suggesting that genicular morphology approaches an engineering optimum, possibly reflecting adaptation to hydrodynamic stress. We measured drag in a re-circulating water flume(0.23–3.6 m s–1) and a gravity-accelerated water flume,which generates jets of water that mimic the impact of breaking waves(6–10 m s–1). We used frond Reynolds number to extrapolate drag coefficients in the field and to predict water velocities necessary to break fronds of given sizes. Laboratory data successfully predicted frond sizes found in the field, suggesting that, although Calliarthron is well adapted to resist breakage, wave forces may ultimately limit the size of intertidal fronds.
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Affiliation(s)
- Patrick T. Martone
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,USA
| | - Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950,USA
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37
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Abstract
For marine algae, the benefits of drying out are often overshadowed by the stresses involved. Here we used laboratory and field experiments to examine both the costs and benefits of desiccation in the intertidal turf alga Endocladia muricata (Endlichter) J. Agardh. Laboratory experiments showed that when Endocladia is dry, photosynthesis stops, but thermotolerance increases to the point that the alga is protected from heat-induced mortality. Drying rates measured in a wind tunnel, combined with tidal data and measured wave splash, indicate that a substantial fraction of the year is spent "drying out" (∼30% of the total time available for photosynthesis). During these periods, the rate of drying determines how much time is spent hydrated and potentially engaged in photosynthesis, but also vulnerable to high temperatures. Turf algae such as Endocladia dry from the edge of a clump inward. Consequently, the clump center remains hydrated longer than the clump edge. The resulting regionalization of a clump results in notable patterns of frond mortality ("fairy rings," and zoned patterns of frond bleaching) within the Endocladia zone.
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Affiliation(s)
- Luke J H Hunt
- Hopkins Marine Station of Stanford University, 120 Oceanview Blvd, Pacific Grove, California 93950, USA
| | - Mark W Denny
- Hopkins Marine Station of Stanford University, 120 Oceanview Blvd, Pacific Grove, California 93950, USA
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Affiliation(s)
- Mark W. Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA
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Mach KJ, Nelson DV, Denny MW. Techniques for predicting the lifetimes of wave-swept macroalgae: a primer on fracture mechanics and crack growth. J Exp Biol 2007; 210:2213-30. [PMID: 17575028 DOI: 10.1242/jeb.001560] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Biomechanical analyses of intertidal and shallow subtidal seaweeds have elucidated ways in which these organisms avoid breakage in the presence of exceptional hydrodynamic forces imposed by pounding surf. However, comparison of algal material properties to maximum hydrodynamic forces predicts lower rates of breakage and dislodgment than are actually observed. Why the disparity between prediction and reality? Most previous research has measured algal material properties during a single application of force, equivalent to a single wave rushing past an alga. In contrast, intertidal macroalgae may experience more than 8000 waves a day. This repeated loading can cause cracks– introduced, for example, by herbivory or abrasion – to grow and eventually cause breakage, yet fatigue crack growth has not previously been taken into account. Here, we present methods from the engineering field of fracture mechanics that can be used to assess consequences of repeated force imposition for seaweeds. These techniques allow quantification of crack growth in wave-swept macroalgae, a first step towards considering macroalgal breakage in the realistic context of repeated force imposition. These analyses can also be applied to many other soft materials.
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Affiliation(s)
- Katharine J Mach
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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40
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Abstract
SUMMARY
Wave-swept macroalgae are subjected to large hydrodynamic forces as each wave breaks on shore, loads that are repeated thousands of times per day. Previous studies have shown that macroalgae can easily withstand isolated impositions of maximal field forces. Nonetheless, macroalgae break frequently. Here we investigate the possibility that repeated loading by sub-lethal forces can eventually cause fracture by fatigue. We determine fracture toughness, in the form of critical strain energy release rate, for several flat-bladed macroalgae, thereby assessing their resistance to complete fracture in the presence of cracks. Critical energy release rates are evaluated through single-edge-notch, pull-to-break tests and single-edge-notch, repeated-loading tests. Crack growth at sub-critical energy release rates is measured in repeated-loading tests, providing a first assessment of algal breakage under conditions of repeated loading. We then estimate the number of imposed waves required for un-notched algal blades to reach the point of complete fracture. We find that, if not checked by repair, fatigue crack growth from repeated sub-lethal stresses may completely fracture individuals within days. Our results suggest that fatigue may play an important role in macroalgal breakage.
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Affiliation(s)
- Katharine J Mach
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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41
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Abstract
SUMMARYLiving at the interface between the marine and terrestrial environments,intertidal organisms may serve as a bellwether for environmental change and a test of our ability to predict its biological consequences. However, current models do not allow us to predict the body temperature of intertidal organisms whose heat budgets are strongly affected by conduction to and from the substratum. Here, we propose a simple heat-budget model of one such animal,the limpet Lottia gigantea, and test the model against measurements made in the field. Working solely from easily measured physical and meteorological inputs, the model predicts the daily maximal body temperatures of live limpets within a fraction of a degree, suggesting that it may be a useful tool for exploring the thermal biology of limpets and for predicting effects of climate change. The model can easily be adapted to predict the temperatures of chitons, acorn barnacles, keyhole limpets, and encrusting animals and plants.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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Abstract
SUMMARY
When coupled with long-term meteorological records, a heat-budget model for the limpet, Lottia gigantea, provides a wealth of information regarding environmental and topographic controls of body temperature in this ecologically important species. (1) The maximum body temperature predicted for any site (37.5°C) is insufficient to kill all limpets, suggesting that acute thermal stress does not set an absolute upper limit to the elevation of L. gigantea on the shore. Therefore, the upper limit must be set by behavioral responses, sublethal effects or ecological interactions. (2)Temperatures sufficient to kill limpets are reached at only a small fraction of substratum orientations and elevations and on only three occasions in 5 years. These rare predicted lethal temperatures could easily be missed in field measurements, thereby influencing the interpretation of thermal stress.(3) Body temperature is typically higher than air temperature, but maximum air temperature can nonetheless be used as an accurate predictor of maximum body temperature. Warmer air temperatures in the future may thus cause increased mortality in this intertidal species. Interpretation of the ecological effects of elevated body temperature depends strongly on laboratory measurements of thermal stress, highlighting the need for additional research on the temporal and spatial variability of thermal limits and sublethal stress. The lengthy time series of body temperatures calculated from the heat-budget model provides insight into how these physiological measurements should be conducted.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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Kitzes JA, Denny MW. Red algae respond to waves: morphological and mechanical variation in Mastocarpus papillatus along a gradient of force. Biol Bull 2005; 208:114-119. [PMID: 15837960 DOI: 10.2307/3593119] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Intertidal algae are exposed to the potentially severe drag forces generated by crashing waves, and several species of brown algae respond, in part, by varying the strength of their stipe material. In contrast, previous measurements have suggested that the material strength of red algae is constant across wave exposures. Here, we reexamine the responses to drag of the intertidal red alga Mastocarpus papillatus Kutzing. By measuring individuals at multiple sites along a known force gradient, we discern responses overlooked by previous methods, which compared groups of individuals between "exposed" and "protected" sites. This improved resolution reveals that material strength and stipe cross-sectional area are both positively correlated with drag, suggesting that individual blades or populations can adjust either or both of these parameters in response to their mechanical environment. The combined effect of this variation is a stipe breaking force that is positively correlated with locally imposed drag. Owing to this response to drag, the estimated wave-imposed limit to thallus size in M. papillatus is larger than previously predicted and larger than sizes observed in the field, indicating that factors other than wave force alone constrain the size of this alga on wave-swept shores.
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Affiliation(s)
- Justin A Kitzes
- Stanford University, Hopkins Marine Station, Pacific Grove, California 93950, USA
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Denny MW, Helmuth B, Leonard GH, Harley CDG, Hunt LJH, Nelson EK. QUANTIFYING SCALE IN ECOLOGY: LESSONS FROM AWAVE-SWEPT SHORE. ECOL MONOGR 2004. [DOI: 10.1890/03-4043] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Abstract
Phenotypic plasticity, the capacity of a given genotype to produce differing morphologies in response to the environment, is widespread among marine organisms (1). For example, acorn barnacles feed by extending specialized appendages (the cirral legs) into flow, and the length of the cirri is plastic: the higher the velocity, the shorter the feeding legs (2,3). However, this effect has been explored only for flows less than 4.6 m/s, slow compared to typical flows measured at sites on wave-exposed shores. What happens at faster speeds? Leg lengths of Balanus glandula Darwin, 1854, an acorn barnacle, were measured at 15 sites in Monterey, California, across flows ranging from 0.5 to 14.0 m/s. Similar to previous findings, a plastic response in leg length was noted for the four sites with water velocities less than 3 m/s. However, no plastic response was present at the 11 sites exposed to faster velocities, despite a 4-fold variation in speed. We conclude that the velocity at which the plastic response occurs has an upper limit of 2-4 m/s, a velocity commonly exceeded within the typical habitat of this species.
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Affiliation(s)
- Natasha K Li
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA.
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Abstract
SUMMARY
The mechanism by which surface tension allows water striders (members of the genus Gerris) to stand on the surface of a pond or stream is a classic example for introductory classes in animal mechanics. Until recently,however, the question of how these insects propelled themselves remained open. One plausible mechanism–creating momentum in the water via the production of capillary waves–led to a paradox: juvenile water striders move their limbs too slowly to produce waves, but nonetheless travel across the water's surface. Two recent papers demonstrate that both water striders and water-walking spiders circumvent this paradox by foregoing any reliance on waves to gain purchase on the water. Instead they use their legs as oars, and the capillary `dimple' formed by each leg acts as the oar's blade. The resulting hydrodynamic drag produces vortices in the water, and the motion of these vortices imparts the necessary fluid momentum. These studies pave the way for a more thorough understanding of the complex mechanics of walking on water, and an exploration of how this intriguing form of locomotion scales with the size of the organism.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950-3094, USA.
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Abstract
Biomechanical models come in a variety of forms: conceptual models; physical models; and mathematical models (both of the sort written down on paper and the sort carried out on computers). There are model structures (such as insect flight muscle and the tendons of rats' tails), model organisms (such as the flying insect, Manduca sexta), even model systems of organisms (such as the communities that live on wave-swept rocky shores). These different types of models are typically employed separately, but their value often can be enhanced if their insights are integrated. In this brief report we explore a particular example of such integration among models, as applied to flexible marine algae. A conceptual model serves as a template for the construction of a mathematical model of a model species of giant kelp, and the validity of this numerical model is tested using physical models. The validated mathematical model is then used in conjunction with a computer-controlled tensile testing apparatus to simulate the loading regime placed on algal materials. The resulting information can be used to create a more precise mathematical model.
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Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950, USA.
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Denny MW, Nelson EK, Mead KS. Revised estimates of the effects of turbulence on fertilization in the purple sea urchin, Strongylocentrotus purpuratus. Biol Bull 2002; 203:275-277. [PMID: 12480718 DOI: 10.2307/1543570] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Affiliation(s)
- Mark W Denny
- Hopkins Marine Station of Stanford University, Pacific Grove, California 93950, USA.
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50
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Abstract
The diversity of form among benthic marine plants and animals on rocky coasts is remarkable. Stiff and strong organisms grow alongside others that are compliant and flimsy. Given the severity of wave action on many shores and thus the potential for the imposition of large hydrodynamic forces, this immediately raises the question of how, from this overall spectrum of designs, flexible and weak organisms survive. A number of explanations have been proposed, most emphasizing one or more of several possible advantages of deformability. Here, we explore quantitatively two of the more common of these explanations: (i) that strength can be traded against extensibility in allowing stretchy organisms to withstand transient wave forces, and (ii) that greater compliance (and thus longer organism response times) allows universally for the amelioration of brief loads. We find that, although these explanations contain kernels of validity and are accurate for a subset of conditions, they are not as general as has often been assumed.
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Affiliation(s)
- B Gaylord
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA.
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