Climate change is impacting marine ecosystems in increasingly rapid and unpredictable ways. The spatial extent of these impacts on marine fisheries and endangered and threatened species often spans regional and international boundaries. The transboundary nature of changing ocean conditions can challenge detection and anticipation of changes, and delay coordinated actions at the scales required to mitigate and respond. Here, we identify challenges and opportunities for transboundary science in the Northeast Pacific Ocean. Specifically, we aim to support the management of fisheries and protected species in response to a changing climate, while highlighting successful efforts. Challenges include (1) limited coordination of monitoring surveys; (2) institutional, cultural, and technological barriers to the sharing of data and analytical tools; (3) incomplete understanding of relationships among oceanographic conditions, trophic interactions, population dynamics, and species' distributions; (4) limited availability of high-resolution Earth system model projections that can be linked to ecosystem and fishery responses; and (5) differing prioritization of ecosystem information and limited communication among nations. Three opportunities to overcome these challenges include (1) coordinated monitoring and sharing of data at a transboundary scale to detect and understand marine ecosystem responses to climate change; (2) common assessment frameworks and modeling approaches to improve understanding and projections of ecological responses to climate change; and (3) increased communication of ecosystem information to support management needs across jurisdictions, enhance the use of existing science products, and strengthen pathways for science to inform management of marine resources. We focus on examples of these opportunities drawn from our collective experience as government scientists working on Northeast Pacific Ocean ecosystems. We suggest that by strategically focusing on these opportunities, transboundary science worldwide can improve predictions of ecosystem responses to climate change and better support regional and international management of shared resources.

Ecosystem-based fisheries management strives to account for species interactions and ecosystem processes in natural resource management and conservation. In this context, ecosystem-wide caps on total fishery catches have been proposed as one tool to manage multispecies fisheries with an ecosystem approach. However, determining effective ecosystem caps is complicated because fish stock production is influenced by environmental conditions, species interactions, and fishing. Consequently, the implementation of ecosystem caps in fisheries management frameworks remains uncommon. We investigated whether ecosystem caps should account for climate variability and for predator-prey dynamics to achieve management objectives in complex marine ecosystems. We considered the example of the Gulf of Alaska (United States), a North Pacific large marine ecosystem where annual groundfish catches are managed using an "optimum yield" ecosystem cap of 800,000 t. We simulated multispecies yield of the 12 most abundant and commercially valuable groundfish stocks under selected climate and fishing scenarios using an end-to-end marine ecosystem model (Atlantis), which accounts for predator-prey and ecosystem dynamics. We found that total groundfish yield was never projected to exceed the 800,000 mt optimum yield cap across scenarios and fishing mortalities. Projected climate change led to decreased groundfish yield, and predation from the underexploited groundfish predator arrowtooth flounder (Atheresthes stomias) led to foregone catches. Groundfish removals had negative indirect effects on groundfish predators, despite total yield never exceeding the optimum yield cap, highlighting that an ineffective cap may not protect non-target species. These results suggest that the optimum yield cap currently used in the Gulf of Alaska may be too high to constrain groundfish catches under future climate change and low exploitation rates of predators. We propose that ecosystem caps should be reviewed when environmental conditions, stock productivity, or species interactions change.

Ecosystem-based fisheries management requires the successful integration of ecosystem information into the fisheries management process. In the Northeast Pacific Ocean, ecosystem data collection and accessibility have achieved successful milestones, yet application to the harvest specification process remains challenging. The synthesis, interpretation, and application of ecosystem information to groundfish fisheries management in the Gulf of Alaska (GOA) can be supported by the identification of common ecosystem trends and ecosystem states across a diverse set of indicators. In this study, we used Dynamic Factor Analysis (DFA) and hidden Markov models (HMM) to analyze 92 indicators in climate, lower-trophic, mid-trophic, and seabird models for the western and eastern GOA marine ecosystems. Time series ranged from 25 to 52 years in length, analyzed through 2022. The DFA identified common trends across indicators and groups of covarying indicators (e.g., biomass of zooplankton species), highlighting opportunities to streamline communication of these data to management. Non-stationarity analyses revealed past changes in relationships, and can provide early warnings in future annual updates if previously identified correlations change. The HMM identified two to three ecosystem states in each sub-model that largely aligned with previously observed long- and short-term shifts in ecosystem dynamics in the region (i.e., shifts starting in 1975, 1988, and 2014). Annually updating these analyses, within an existing framework of reporting ecosystem information to management bodies, can streamline communication and improve early warning of changes in ecosystem dynamics. These tools can provide ecosystem support to management decisions relative to groundfish productivity and resulting harvest specifications.

Abstract Recent marine heatwaves in the Gulf of Alaska have had devastating impacts on species from various trophic levels. Due to climate change, total heat exposure in the upper ocean has become longer, more intense, more frequent, and more likely to happen at the same time as other environmental extremes. The combination of multiple environmental extremes can exacerbate the response of sensitive marine organisms. Our hindcast simulation provides the first indication that more than 20% of the bottom water of the Gulf of Alaska continental shelf was exposed to quadruple heat, positive hydrogen ion concentration [H+], negative aragonite saturation state (Ωarag), and negative oxygen concentration [O2] compound extreme events during the 2018–2020 marine heat wave. Natural intrusion of deep and acidified water combined with the marine heat wave triggered the first occurrence of these events in 2019. During the 2013–2016 marine heat wave, surface waters were already exposed to widespread marine heat and positive [H+] compound extreme events due to the temperature effect on the [H+]. We introduce a new Gulf of Alaska Downwelling Index (GOADI) with short‐term predictive skill, which can serve as indicator of past and near‐future positive [H+], negative Ωarag, and negative [O2] compound extreme events near the shelf seafloor. Our results suggest that the marine heat waves may have not been the sole environmental stressor that led to the observed ecosystem impacts and warrant a closer look at existing in situ inorganic carbon and other environmental data in combination with biological observations and model output.

As climate stressors are impacting marine ecosystems and fisheries across the world, ecosystem models that incorporate environmental variables are increasingly used to inform ecosystem-based fisheries management. The assumptions around the mechanistic links between climate stressors and the biological processes in these models are important, but the implications for model outcomes of which stressors are captured and how they affect modeled biological processes are seldom explored. Using a whole-ecosystem model (Atlantis) for the Gulf of Alaska, we explore the effects of capturing physical (increased temperature) and biogeochemical (decreased low trophic level productivity) climate stressors, and disentangle the effects of each stressor on the productivity of forage fish, groundfish, and fish-eating seabirds. We then test the effects of alternative model specifications of temperature-driven habitat determination and bioenergetics. Increased temperature resulted in increased weight-at-age and higher natural mortality, while decreased productivity resulted in decreased weight-at-age and higher natural mortality. Model specification of temperature dependence of movement and spawning influenced model outcomes, and decoupling these processes from temperature led to overly optimistic biomass predictions. As the use of ecosystem models to inform fisheries management becomes more operational, we illustrate that the assumptions around the links between climate stressors and ecological processes influence model outcomes.

ObjectiveOyster reefs across North America have declined precipitously over the past 140 years. In Washington State, Olympia oyster Ostrea lurida reefs historically provided water filtration and nearshore structural habitat for fishes and invertebrates, but this species is now functionally extinct across its historical range. In place of these naturally occurring reefs, shellfish farms consisting mainly of nonnative Pacific oysters Magallana gigas now occupy patches of nearshore habitat across Washington. These farms modify intertidal substrate by adding structural habitat via suspended oyster grow bags, predator exclusion nets, loose oyster beds, and other shellfish grow-out gear. As interest and investment in shellfish aquaculture have expanded both locally and globally, so has interest in how these farms modify intertidal habitat and whether the complex structure created by the shellfish and shellfish growing gear provides ecosystem services that are comparable to those of unfarmed areas, such as mudflats and eelgrass meadows.MethodsIn this study, we sought to quantify how shellfish farms are used as foraging habitat for several common nearshore species of fish and crabs in Puget Sound, Washington. We used direct observations of species-specific behaviors from underwater video to model how habitat type affected observed foraging rates.ResultWe obtained a total of 393 crab observations, 431 demersal fish observations, and 1856 pelagic fish observations across all seven farm sites. Several common species of pelagic fish (e.g., surfperch [Embiotocidae]) used aquaculture-growing gear more frequently than unfarmed areas as foraging habitat, but Metacarcinus spp. crabs displayed higher foraging frequency in unfarmed mudflats. Species groups such as sculpins (Cottidae) and small flatfish (Pleuronectidae) clearly used specific aquaculture-growing gear and mudflats in roughly equal proportion.ConclusionOur results indicate that shellfish farms within a larger nearshore habitat mosaic of eelgrass meadows, mudflats, bivalve aquaculture gear, and edge habitat can provide foraging habitat for several species of nearshore fish. Shellfish farms within a larger nearshore habitat mosaic of eelgrass meadows, mudflats, bivalve aquaculture gear, and edge habitat can provide foraging habitat for several species of nearshore fish.Impact statement

Humans are exposed to toxic methylmercury mainly by consuming marine fish. While reducing mercury emissions and releases aims to protect human health, it is unclear how this affects methylmercury concentrations in seawater and marine biota. We compiled existing and newly acquired mercury concentrations in tropical tunas from the global ocean to explore multidecadal mercury variability between 1971 and 2022. We show the strong inter-annual variability of tuna mercury concentrations at the global scale, after correcting for bioaccumulation effects. We found increasing mercury concentrations in skipjack in the late 1990s in the northwestern Pacific, likely resulting from concomitant increasing Asian mercury emissions. Elsewhere, stable long-term trends of tuna mercury concentrations contrast with an overall decline in global anthropogenic mercury emissions and deposition since the 1970s. Modeling suggests that this limited response observed in tunas likely reflects the inertia of surface ocean mercury with respect to declining emissions, as it is supplied by legacy mercury that accumulated in the subsurface ocean over centuries. To achieve measurable declines in mercury concentrations in highly consumed pelagic fish in the near future, aggressive emission reductions and long-term and continuous mercury monitoring in marine biota are needed.

Synthesis research in ecology and environmental science improves understanding, advances theory, identifies research priorities, and supports management strategies by linking data, ideas, and tools. Accelerating environmental challenges increases the need to focus synthesis science on the most pressing questions. To leverage input from the broader research community, we convened a virtual workshop with participants from many countries and disciplines to examine how and where synthesis can address key questions and themes in ecology and environmental science in the coming decade. Seven priority research topics emerged: (1) diversity, equity, inclusion, and justice (DEIJ), (2) human and natural systems, (3) actionable and use-inspired science, (4) scale, (5) generality, (6) complexity and resilience, and (7) predictability. Additionally, two issues regarding the general practice of synthesis emerged: the need for increased participant diversity and inclusive research practices; and increased and improved data flow, access, and skill-building. These topics and practices provide a strategic vision for future synthesis in ecology and environmental science.

The sustainable management of fisheries and aquaculture requires an understanding of how these activities interact with natural fish populations. GoPro cameras were used to collect an underwater video data set on and around shellfish aquaculture farms in an estuary in the NE Pacific from June to August 2017 and June to August 2018 to better understand habitat use by the local fish and crab communities. Images extracted from these videos were labeled to produce a data set that is suitable for use in training computer vision models. The labeled data set contains 77,739 images sampled from the collected video; 67,990 objects (fishes and crustaceans) have been annotated in 30,384 images (the remainder have been annotated as “empty”). The metadata of the data set also indicates whether a physical magenta filter was used during video collection to counteract reduced visibility. These data have the potential to help researchers address system-level and in-depth regional shellfish aquaculture questions related to ecosystem services and shellfish aquaculture interactions.

Integrating social and ecological aspects of bivalve aquaculture in research and management processes can improve understanding of the system as a whole, and facilitate management decision-making. We created social-ecological conceptual models of Pacific oyster (Crassostrea gigas), Manila clam (Venerupis philippinarum), and Pacific geoduck (Panopea generosa) aquaculture in a USA estuary, which were the basis of qualitative network analysis to compare: (i) social-ecological models versus truncated ecological- and social- only models, and (ii) two geoduck models representing different stakeholder groups' perspectives on nature-based recreation and environmental stewardship. The social-ecological models predicted different results compared to individual social or ecological models, including for abundance of invertebrates, eelgrass, and marine water quality. The two alternative geoduck models predicted outcomes that varied across multiple social-ecological variables, including the availability of local harvestable food, sense of place, and abundance of invertebrates in structured habitat. Results demonstrate the interconnectedness of the social and ecological components of the aquaculture system, and how predicted outcomes can vary depending on their inclusion in the model. This study also demonstrates the value in considering a suite of models that represents a range of group perspectives to identify areas of conflict and agreement, and to recognize bias inherent in the models.

Bivalve aquaculture is an expanding coastal industry with the potential to modify the habitat of fish and crab species, affecting their refuge, movement, and feeding. The habitat function of shellfish aquaculture is not yet well understood, in part due to difficulties in data collection using traditional methods. Underwater video was used to observe fish and crab species’ affiliations with cultured Pacific oyster Crassostrea gigas and Manila clam Venerupis philippinarum aquaculture sites in comparison to uncultured reference sediment and eelgrass habitats. Sites were monitored in 9 locations across 3 regions of Puget Sound, Washington, USA, in the summers of 2017 and 2018. Of the 3038 fish and crabs observed, 98% were represented by Embiotocidae (surfperch), crabs, three-spined stickleback Gasterosteus aculeatus, Cottidae (sculpins), and Pleuronectiformes (flatfish). Overall, the affiliations of fish and crabs with bivalve aquaculture varied by species groups, culture type, and regional environmental and habitat conditions. These interactions varied on a scale of approximately 150 km, highlighting variation of aquaculture-ecological interactions at a scale not previously recorded in Puget Sound. Species composition varied between aquaculture and non-aquaculture habitats in 2 of the 3 regions studied. Species diversity and richness in aquaculture habitats varied regionally, relative to reference habitats. Pelagic species were more abundant in aquaculture and reference sites that had vertical structure, but abundances of demersal and benthic species on aquaculture habitat relative to reference sites varied regionally. The availability of habitats within intertidal regions, including varying types of aquaculture, could determine community structure for marine organisms such as fish and crab.

Domoic acid (DA)-producing harmful algal blooms (HABs) have been present at unprecedented geographic extent and duration in recent years causing an increase in contamination of seafood by this common environmental neurotoxin. The toxin is responsible for the neurotoxic illness, amnesic shellfish poisoning (ASP), that is characterized by gastro-intestinal distress, seizures, memory loss, and death. Established seafood safety regulatory limits of 20 μg DA/g shellfish have been relatively successful at protecting human seafood consumers from short-term high-level exposures and episodes of acute ASP. Significant concerns, however, remain regarding the potential impact of repetitive low-level or chronic DA exposure for which there are no protections. Here, we report the novel discovery of a DA-specific antibody in the serum of chronically-exposed tribal shellfish harvesters from a region where DA is commonly detected at low levels in razor clams year-round. The toxin was also detected in tribal shellfish consumers’ urine samples confirming systemic DA exposure via consumption of legally-harvested razor clams. The presence of a DA-specific antibody in the serum of human shellfish consumers confirms long-term chronic DA exposure and may be useful as a diagnostic biomarker in a clinical setting. Adverse effects of chronic low-level DA exposure have been previously documented in laboratory animal studies and tribal razor clam consumers, underscoring the potential clinical impact of such a diagnostic biomarker for protecting human health. The discovery of this type of antibody response to chronic DA exposure has broader implications for other environmental neurotoxins of concern.

Information on ocean scale drivers of methylmercury levels and variability in tuna is scarce, yet crucial in the context of anthropogenic mercury (Hg) inputs and potential threats to human health. Here we assess Hg concentrations in three commercial tuna species (bigeye, yellowfin, and albacore, n = 1000) from the Western and Central Pacific Ocean (WCPO). Models were developed to map regional Hg variance and understand the main drivers. Mercury concentrations are enriched in southern latitudes (10°S-20°S) relative to the equator (0°-10°S) for each species, with bigeye exhibiting the strongest spatial gradients. Fish size is the primary factor explaining Hg variance but physical oceanography also contributes, with higher Hg concentrations in regions exhibiting deeper thermoclines. Tuna trophic position and oceanic primary productivity were of weaker importance. Predictive models perform well in the Central Equatorial Pacific and Hawaii, but underestimate Hg concentrations in the Eastern Pacific. A literature review from the global ocean indicates that size tends to govern tuna Hg concentrations, however regional information on vertical habitats, methylmercury production, and/or Hg inputs are needed to understand Hg distribution at a broader scale. Finally, this study establishes a geographical context of Hg levels to weigh the risks and benefits of tuna consumption in the WCPO.

The marine, intertidal zone is the optimal environment for eelgrass (Zostera spp.) and bivalve aquaculture. Eelgrass is a valuable and protected nearshore habitat. It is important to understand how bivalve aquaculture interacts with eelgrass to support the sustainable development of this globally expanding industry. This study provides a comprehensive understanding of the positive and negative effects of bivalve aquaculture on eelgrass by conducting the first quantitative, global meta-analysis of aquaculture-eelgrass studies. A literature review resulted in 125 studies that met established criteria for inclusion in this analysis. The meta-analysis determined: (1) how eelgrass responds to on-bottom and off-bottom bivalve aquaculture, (2) how these responses vary between regions and specific grow-out methods, and (3) the resilience of eelgrass after harvesting disturbances. On-bottom culture (laying directly on the sediment potentially including predator exclusion devices) corresponded to significant increases in eelgrass growth and reproduction, and a decrease in density and biomass. Off-bottom culture (e.g., longline and suspended bag) resulted in significant decreases in eelgrass density, percent cover, and reproduction. Results support a space-competition hypothesis for on-bottom culture and provide limited support for light limitation in off-bottom culture, although other mechanisms of interaction are potentially occurring as well. A US west coast case study revealed regional differences in eelgrass responses, including a more negative trend in eelgrass density from off-bottom culture, and a neutral effect on reproduction from on-bottom culture (relative to neutral and positive trend, respectively, in the average of all other studies). Eelgrass densities recovered after all harvest methods, however mechanical harvest methods created greater initial impact and longer recovery times than manual harvest methods. The time-period over which observations were reported was an important variable that was not included in the analysis but could influence these results. These analyses suggest the response of eelgrass to bivalve aquaculture varies depending on eelgrass characteristics, grow-out approaches, and harvesting methods, with potential regionally specific relationships. Questions remain, regarding how this dynamic relationship between eelgrass and aquaculture habitat relates to ecological functions and services in the nearshore environment.

The consumption of one meal of seafood containing domoic acid (DA) at levels high enough to induce seizures can cause gross histopathological lesions in hippocampal regions of the brain and permanent memory loss in humans and marine mammals. Seafood regulatory limits have been set at 20mgDA/kg shellfish to protect human consumers from symptomatic acute exposure, but the effects of repetitive low-level asymptomatic exposure remain a critical knowledge gap. Recreational and Tribal-subsistence shellfish harvesters are known to regularly consume low levels of DA. The aim of this study was to determine if chronic low-level DA exposure, at doses below those that cause overt signs of neurotoxicity, has quantifiable impacts on cognitive function. To this end, female C57BL/6NJ mice were exposed to asymptomatic doses of DA (≈0.75mg/kg) or vehicle once a week for several months. Spatial learning and memory were tested in a radial water maze paradigm at one, six and 25 weeks of exposure, after a nine-week recovery period following cessation of exposure, and at three old age time points (18, 24 and 28 months old). Mice from select time points were also tested for activity levels in a novel cage environment using a photobeam activity system. Chronic low-level DA exposure caused significant spatial learning impairment and hyperactivity after 25 weeks of exposure in the absence of visible histopathological lesions in hippocampal regions of the brain. These cognitive effects were reversible after a nine-week recovery period with no toxin exposure and recovery was sustained into old age. These findings identify a new potential health risk of chronic low-level exposure in a mammalian model. Unlike the permanent cognitive impacts of acute exposure, the chronic low-level effects observed in this study were reversible suggesting that these deficits could potentially be managed through cessation of exposure if they also occur in human seafood consumers.

Domoic acid (DA) is a neurotoxin that is naturally produced by phytoplankton and accumulates in seafood during harmful algal blooms. As the prevalence of DA increases in the marine environment, there is a critical need to identify seafood consumers at risk of DA poisoning. DA exposure was estimated in recreational razor clam (Siliqua patula) harvesters to determine if exposures above current regulatory guidelines occur and/or if harvesters are chronically exposed to low levels of DA. Human consumption rates of razor clams were determined by distributing 1523 surveys to recreational razor clam harvesters in spring 2015 and winter 2016, in Washington, USA. These consumption rate data were combined with DA measurements in razor clams, collected by a state monitoring program, to estimate human DA exposure. Approximately 7% of total acute exposures calculated (including the same individuals at different times) exceeded the current regulatory reference dose (0.075mgDA·kgbodyweight-1·d-1) due to higher than previously reported consumption rates, lower bodyweights, and/or by consumption of clams at the upper range of legal DA levels (maximum 20mg·kg-1 wet weight for whole tissue). Three percent of survey respondents were potentially at risk of chronic DA exposure by consuming a minimum of 15 clams per month for at 12 consecutive months. These insights into DA consumption will provide an additional tool for razor clam fishery management.

Predicting the effects of aquaculture development for coastal ecosystems remains challenging, particularly for data-limited systems, and tools that account for complex ecological interactions are needed to support ecosystem approaches to aquaculture. Here, we used qualitative network models (QNMs) to examine the potential community effects of increasing bivalve aquaculture in South Puget Sound, a large estuarine system in Washington, United States. QNMs are formalized conceptual models that require only a qualitative understanding of how variables composing a system interact (that is, the sign of interactions: +, -, and 0) and are therefore well-suited to data-limited systems. Specifically, we examined community-wide responses to scenarios in which bivalve cultivation effort increased for three different bivalve species (Manila clam Venerupis philippinarum, Pacific oyster Crassostrea gigas, and geoduck Panopea generosa). Further, we evaluated community-wide responses to the removal of benthic bivalve predators, a future increase in nutrient loadings, and combinations of these scenarios acting simultaneously. The scenarios enabled identification of potential trade-offs between increased aquaculture and shifts in the abundance of community members and assessment of the possible effects of different management actions. We also analysed the QNM to identify key interactions that influence the sign outcome of community responses to press perturbations, highlighting potential points for management intervention and linkages deserving of more focused quantitative study. QNMs are mathematically robust and highly flexible, but remain underutilized. We suggest that they may serve as valuable tools for supporting ecosystem approaches to aquaculture.

Expansion of the shellfish aquaculture industry has the potential to affect the structure and dynamics of coastal estuarine foodwebs. To better understand foodweb trade-offs, we incorporated both trophic and non-trophic interactions (e.g. habitat facilitation and predator refuge) into a foodweb model of central Puget Sound to predict the effects of an increase in geoduck (Panopea generosa) aquaculture. At a basin scale, the foodweb can support at least 120% increased geoduck aquaculture, above current production levels (landings of 10 546 kg in 2012), with only minor changes in individual species' biomass and/or metrics of ecosystem resilience. The non-trophic effects of increased geoduck aquaculture, related to the influence of anti-predator structure, had a stronger influence on the foodweb than the trophic role of cultured geoducks as filter-feeders and prey to other species. Increased geoduck culture caused substantial increases in biomass densities of surfperch, nearshore demersal fish, and small crabs, and decreases in seabirds, flatfish, and certain invertebrates (e.g. predatory gastropods and small crustaceans). This study identifies species that should be a priority for additional empirical research and monitoring related to bivalve aquaculture interactions, including demersal fish, small crustaceans, and seabirds. It also provides insights into the benefits and challenges of incorporating habitat-related data into a foodweb model. Understanding these relationships can inform management decisions by clarifying trade-offs in ecosystem functions and services in Puget Sound and facilitates estimation of direct and cumulative effects of bivalve aquaculture at a foodweb scale.