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The Gulf of Maine is a highly productive and economically important region in the northwestern Atlantic that has undergone rapid warming in recent decades and is susceptible to ocean acidification (OA). These stressors may have substantial impacts on local fisheries. Therefore, understanding the combined effects of warming and OA to commercially important shellfish is vital. To test responses to warming and OA, Mercenaria mercenaria (hard clam), Mya arenaria (soft-shell clam), Plactopectin magellanicus (sea scallop), and both juvenile and adult Arctica islandica (ocean quahog) were grown in flowing seawater tanks for 20.5 weeks in controlled pH (7.4, 7.6, 7.8 or 8.0 (ambient) ± 0.02) and temperature (6, 9 or 12 ± 0.56 °C) conditions at Bowdoin College’s Schiller Coastal Studies Center. The specimens’ diet was supplemented with high-quality food (Shellfish Diet) throughout the experiment. Temperature effects were a significant contributor in all shell growth metrics (maximum height, dry weight and buoyant weight) in all species except the height and dry weight of adult A. islandica. Additionally, pH effects were significant in the height of M. mercenaria and in the dry weight of juvenile A. islandica samples. Overall, mortality rates ranged from 1.5% in juvenile A. islandica to 24% in M. mercenaria, with results varying by species and treatment conditions. Additionally, differences in final shell condition were noted among the various treatments indicating that, although most of the organisms survived and grew, the elevated temperature and/or lower pH conditions might not have been ideal for thriving. Considering all results of growth and survival, the four species showed a differential response to the same warming and acidification conditions. As suggested by prior research, the availability of high-quality food may allow certain species to tolerate the future warming and/or OA conditions modeled in this experiment. Experimental results may reveal the species-specific resiliency of economically valuable shellfish to changing ocean conditions as well as guide future planning to safeguard regional ecosystems and fisheries.
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Biogeography of ocean acidification: Differential field performance of transplanted mussels to upwelling-driven variation in carbonate chemistry.
Ocean acidification (OA) represents a serious challenge to marine ecosystems. Laboratory studies addressing OA indicate broadly negative effects for marine organisms, particularly those relying on calcification processes. Growing evidence also suggests OA combined with other environmental stressors may be even more deleterious. Scaling these laboratory studies to ecological performance in the field, where environmental heterogeneity may mediate responses, is a critical next step toward understanding OA impacts on natural communities. We leveraged an upwelling-driven pH mosaic along the California Current System to deconstruct the relative influences of pH, ocean temperature, and food availability on seasonal growth, condition and shell thickness of the ecologically dominant intertidal mussel Mytilus californianus. In 2011 and 2012, ecological performance of adult mussels from local and commonly sourced populations was measured at 8 rocky intertidal sites between central Oregon and southern California. Sites coincided with a large-scale network of intertidal pH sensors, allowing comparisons among pH and other environmental stressors. Adult California mussel growth and size varied latitudinally among sites and inter-annually, and mean shell thickness index and shell weight growth were reduced with low pH. Surprisingly, shell length growth and the ratio of tissue to shell weight were enhanced, not diminished as expected, by low pH. In contrast, and as expected, shell weight growth and shell thickness were both diminished by low pH, consistent with the idea that OA exposure can compromise shell-dependent defenses against predators or wave forces. We also found that adult mussel shell weight growth and relative tissue mass were negatively associated with increased pH variability. Including local pH conditions with previously documented influences of ocean temperature, food availability, aerial exposure, and origin site enhanced the explanatory power of models describing observed performance differences. Responses of local mussel populations differed from those of a common source population suggesting mussel performance partially depended on genetic or persistent phenotypic differences. In light of prior research showing deleterious effects of low pH on larval mussels, our results suggest a life history transition leading to greater resilience in at least some performance metrics to ocean acidification by adult California mussels. Our data also demonstrate “hot” (more extreme) and “cold” (less extreme) spots in both mussel responses and environmental conditions, a pattern that may enable mitigation approaches in response to future changes in climate.
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- Award ID(s):
- 1851462
- PAR ID:
- 10278871
- Editor(s):
- Griffen, Blaine D.
- Date Published:
- Journal Name:
- PloS one
- Volume:
- 15
- Issue:
- 7
- ISSN:
- 1932-6203
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Bivalves frequently withstand shell damage that must be quickly repaired to ensure survival. While the processes that underlie larval shell development have been extensively studied within the context of ocean acidification (OA), it remains unclear whether shell repair is impacted by elevated pCO2. To better understand the stereotypical shell repair process, we monitored mussels (Mytilus edulis) with sublethal shell damage that breached the mantle cavity within both field and laboratory conditions to characterize the deposition rate, composition, and integrity of repaired shell. Results were then compared with a laboratory experiment wherein mussels (Mytilus trossulus) repaired shell damage in one of seven pCO2 treatments (400–2500 µatm). Shell repair proceeded through distinct stages; an organic membrane first covered the damaged area (days 1–15), followed by the deposition of calcite crystals (days 22–43) and aragonite tablets (days 51–69). OA did not impact the ability of mussels to close drill holes, nor the microstructure, composition, or integrity of end-point repaired shell after 10 weeks, as measured by µCT and SEM imaging, energy-dispersive X-ray (EDX) analysis, and mechanical testing. However, significant interactions between pCO2, the length of exposure to treatment conditions, the strength and inorganic content of shell, and the physiological condition of mussels within OA treatments were observed. These results suggest that while OA does not prevent adult mussels from repairing or mineralizing shell, both OA and shell damage may elicit stress responses that impose energetic constraints on mussel physiology.more » « less
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Cyr, Frédéric (Ed.)Modern calcifying marine organisms face numerous environmental stressors, including overfishing, deoxygenation, increasing ocean temperatures, and ocean acidification (OA). Coastal marine settings are predicted to become warmer and more acidic in coming decades, heightening the risks of extreme events such as marine heat waves. Given these threats, it is important to understand the vulnerabilities of marine organisms that construct their shells from calcium carbonate, which are particularly susceptible to warming and decreasing pH levels. To investigate the response of four commercially relevant bivalve species to OA and differing temperatures, juvenileMercenaria mercenaria(hard shell clams), juvenileMya arenaria(soft shell clams), adult and juvenileArctica islandica(ocean quahog), and juvenilePlacopecten magellanicus(Atlantic sea scallops) were grown in varying pH and temperature conditions. Species were exposed to four controlled pH conditions (7.4, 7.6, 7.8, and ambient/8.0) and three controlled temperature conditions (6, 9, and 12°C) for 20.5 weeks and then shell growth and coloration were analyzed. This research marks the first direct comparison of these species’ biological responses to both temperature and OA conditions within the same experiment. The four species exhibited varying responses to temperature and OA conditions. Mortality rates were not significantly associated with pH or temperature conditions for any of the species studied. Growth (measured as change in maximum shell height) was observed to be higher in warmer tanks for all species and was not significantly impacted by pH. Two groups (juvenileM.arenariaand juvenileM.mercenaria) exhibited lightening in the color of their shells at lower pH levels at all temperatures, attributed to a loss of shell periostracum. The variable responses of the studied bivalve species, despite belonging to the same phylogenetic class and geographic region, highlights the need for further study into implications for health and management of bivalves in the face of variable stressors.more » « less
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Coastal systems can exhibit large variability in pH compared to open marine conditions, thus the impacts of ocean acidification (OA) on their resident calcifying organisms are potentially magnified. Further, our understanding of the natural baseline and variability of pH is spatially and temporally limited in coastal settings. In the few coastal locations that have been monitoring seawater pH, records are generally limited to <10 years and are thus unable to provide the full range of centennial to decadal natural variability. This is the case for the Gulf of Maine (northwestern Atlantic), a highly productive region of strategic importance to U.S. fisheries, that is facing multiple environmental stressors including rapid warming and threats from OA. Paleoceanographic proxy records are therefore much needed in this region to reconstruct past pH conditions beyond instrumental records. A clear candidate for this is the boron isotope (d11B) pH proxy provided the d11B sensitivity to pH in long-lived shallow water marine carbonates can be established. To this end, we grew juvenile and adult Arctica islandica (ocean quahog) in flowing seawater tanks for 20.5 weeks in controlled pH (7.4, 7.6, 7.8 or 8.0 (ambient) ± 0.02) and temperature (6, 9 or 12 ± 0.56 °C) conditions at Bowdoin College’s Schiller Coastal Studies Center, Harpswell, Maine (USA). The clams were stained twice with calcein and supplemented with food (Shellfish Diet) throughout the experiment to ensure suitable growth. New shell growth (average 67% increase in maximum shell height and 522% increase in buoyant weight across all treatments), constrained by calcein markings, were sampled for boron isotope analysis (d11B) to determine if shell d11B varied as a function of pH similar to many other calcifying organisms. The results of the culture experiment will yield whether or not Arctica islandica preserves seawater pH information in their shells. If so, the transfer function relating shell d11B to pH will be used to hindcast pH in the central coastal region of the Gulf of Maine during recent centuries. Alternatively, if the shell d11B signal is independent of ambient seawater pH, this may reveal the capacity of Arctica islandica to regulate internal calcifying fluid chemistry and their resilience to OA.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.pone.0234075
