OA Research Highlights Around the Region: Part 2

OA Research Highlights Around the Region: Part 2

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Overview

A Dynamic Pathway to Transition from Vulnerable to Resilient Fisheries Social Ecological Systems: A Transdisciplinary Case Study of the US Atlantic Sea Scallop Fishery

Dr. Samantha Siedlecki

<p><a href="https://uconn.edu/" target="_blank" rel="noopener">University of Connecticut</a></p>

Dynamic social ecological systems (SES) built around fishing stocks with potential for sustainable catch and flexibility to respond to changing environmental conditions are key to achieving multiple U.N. Sustainable Development Goals.

Atlantic sea scallops (sea scallops) have demonstrated the potential for sustainable yield, but are increasingly threatened by effects of ocean warming and acidification and the current management system is not climate ready. As calcifiers with limited mobility and high revenue potential, this fishery is particularly suited to a transdisciplinary approach combining coastal fishing community assessments with sea scallop population dynamics, ocean models, and sea scallop physiological response. The vulnerability and resilience of fishing communities to the effects of warming and ocean acidification (OA) on target species such as sea scallops is dependent on their adaptive capacity in relation to both social and environmental exposure and sensitivity factors.

In the Northeast United States, the contribution of sea scallops to total regional landed value has steadily increased over recent decades to more than $500 million per year. As a result, the dependence of the regional fisheries SES has shifted to this species. This dependence, and the predicted shift in sea scallop distribution and biomass decline, make this study particularly relevant. Here, we provide spatially explicit regional projections of changes within the existing sea scallop fishing zones based on ocean models and physiological assessment of the environmental conditions and likely impacts to scallop growth to harvest size. These projections have been combined with social indicators of fishing community vulnerability and reliance to structure workshops with fishery managers and fishing-dependent communities. The workshops assist stakeholders to explore scenarios to become more resilient to future change. Challenges, lessons learned, and next steps toward achieving a transdisciplinary understanding of SES vulnerability in this fishery are explored.

Sustaining Chesapeake Bay Oyster Livelihoods in the Face of Ocean Acidification and Multiple Stressors: An Integrated Assessment of Social-Ecological Thresholds

Brian Katz

<p><a href="https://oregonstate.edu/" target="_blank" rel="noopener">Oregon State University</a></p>

Chesapeake Bay relies heavily on oyster aquaculture, restoration, and harvesting by watermen for its economy and ecosystem. However, multiple stressors such as ocean acidification, changes in salinity, and temperature extremes threaten these livelihoods and have the potential to exceed social-ecological thresholds. This study integrates biophysical and social data using a top-down approach and spatialized interviews collected from the bottom-up to provide a comprehensive assessment of the factors affecting oyster livelihoods in Chesapeake Bay.

We used a random forest regression analysis to identify the relative importance of biogeochemistry and species responses on Eastern oyster (Crassostrea virginica) aquaculture production, revealing that salinity was the most significant predictor, followed by water temperature and dissolved oxygen. Low salinity events coincide with reductions in calcite saturation state, leading to negative impacts on oyster growth and calcification and subsequent declines in production. We also conducted spatialized interviews with aquaculture producers and restoration partners to contextualize and validate our analysis, collecting qualitative data on observed stressors and responses.

Our interviews revealed that growers are concerned about the potential impacts of low salinity events and multiple stressors, and that some social-ecological thresholds may be exceeded if these impacts continue to intensify. However, we also found evidence of adaptive capacity, as growers are implementing measures such as diversifying their livelihoods and investing in new technologies to mitigate the effects of stressors.

Our study highlights the need for integrated and interdisciplinary approaches to managing Chesapeake Bay oyster livelihoods that consider the complex interactions between biophysical and social factors and account for adaptive capacity. Our findings can inform management strategies aimed at promoting sustainable oyster production and restoration in the face of multiple stressors, including ocean acidification.

Examining Climate Change Impacts on York River Carbonate Chemistry and Oyster Growth

Catherine Czajka

<p><a href="https://www.vims.edu/" target="_blank" rel="noopener">Virginia Institute of Marine Science</a></p>

Anthropogenic climate change and its associated impacts on water quality challenge marine species to acclimatize to their altered environment, particularly in estuarine and coastal systems. Increasing oceanic uptake of atmospheric carbon dioxide (CO2) and greater riverine nutrient loads cause decreases in seawater pH and saturation states (W) of calcium carbonate, a phenomenon known as coastal acidification. Due to the natural spatiotemporal variability of biogeochemistry in estuarine systems like the York River, the effects of acidification and other interacting climate change drivers, such as atmospheric warming, will likely not be uniform throughout the bay. Furthermore, it is still unclear in which regions calcifying organisms, like Eastern oysters, will be most vulnerable to future conditions.

To determine how future coastal acidification and atmospheric warming will affect carbonate chemistry and oyster growth in the York River, simulations were run using an oyster bioenergetics model embedded in a 3-D coupled hydrodynamic-biogeochemistry model. Specifically, model runs forced with future (mid-21st century) atmospheric CO2 alone, future atmospheric warming alone, and both forcings together were compared with a realistic 2016 reference run. While increased atmospheric CO2 reduced ambient W and slowed oyster shell growth, atmospheric warming offset this effect and, in some areas, led to an overall increase in shell growth. The results of this work will be used to inform stakeholders of which areas in the Bay will be most suitable for oyster aquaculture and restoration in the future.

Wild-n-wacky or bred-n-butter: are larvae from selectively-bred aquaculture broodstock more resilient to climate change than those from wild Eastern oysters, Crassostrea virginica?

Annie Schatz

<p><a href="https://www.vims.edu/" target="_blank" rel="noopener">Virginia Institute of Marine Science</a></p>

Eastern oysters (Crassostrea virginica) provide ecosystem (e.g. 3-D reef structures) and economic (e.g. aquaculture) services to the Chesapeake Bay and other coastal areas. Oyster aquaculture is a growing industry, and the need for traits such as fast growth and disease resistance led to the development of multiple generations of selectively-bred and refined broodstock lines. Development and preservation of selected broodstock could affect various physiological processes in offspring that could potentially result in different responses to stress compared to their wild counterparts.

As environmental conditions within the Chesapeake Bay continue to shift warmer and more acidic – which are individually and simultaneously known to decrease shell and tissue growth, decrease energy stores, change metabolic pathways and affect development – responses to these conditions may differ between selectively-bred and wild oysters, potentially affecting their success in the future. Because larval oysters are considered the most vulnerable and sensitive life stage and therefore are already a bottleneck to the success of wild oyster populations and aquaculture production, my study exposed larvae from wild oysters and selectively-bred broodstock to four treatments composed of two temperature and two acidic conditions that represent average ambient and current extreme states in the mesohaline region of the Chesapeake Bay. Growth, biomass, cellular stress, and survival were measured throughout showing that larvae from wild oysters may be more resilient to warming and acidifying waters than those from selectively-bred oysters.