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Abstract Climate change is a looming threat to marine life, creating an urgent need to develop climate-informed conservation strategies. The Climate Risk Index for Biodiversity was designed to assess the climate risk for marine species in a manner that supports decision-making. Yet, its regional application remains to be explored. Here, we use it to evaluate climate risk for ~2000 species in the northwest Atlantic Ocean, a marine warming hotspot, to explore its capacity to inform climate-considered fisheries management. Under high emissions, harvested species, especially those with the highest economic value, have a disproportionate risk of projected exposure to hazardous climate conditions but benefit the most from emission mitigation. By mapping critical risk areas for 90 fish stocks, we pinpoint locations likely to require additional intervention, such as in the southern Gulf of St. Lawrence for Atlantic cod. Finally, we demonstrate how evaluating climate risk geographically and understanding how it arises can support short- and long-term fisheries management and conservation objectives under climate change.

Abstract A global decline in seagrass populations has led to renewed calls for their conservation as important providers of biogenic and foraging habitat, shoreline stabilization and carbon storage. Eelgrass (Zostera marina) occupies the largest geographic range among seagrass species spanning a commensurately broad spectrum of environmental conditions. In Canada, eelgrass is managed as a single phylogroup despite occurring across three oceans and a range of ocean temperatures and salinity gradients. Previous research has focused on applying relatively few markers to reveal population structure of eelgrass, whereas a whole‐genome approach is warranted to investigate cryptic structure among populations inhabiting different ocean basins and localized environmental conditions. We used a pooled whole‐genome re‐sequencing approach to characterize population structure, gene flow and environmental associations of 23 eelgrass populations ranging from the Northeast United States to Atlantic, subarctic and Pacific Canada. We identified over 500,000 SNPs, which when mapped to a chromosome‐level genome assembly revealed six broad clades of eelgrass across the study area, with pairwise FST ranging from 0 among neighbouring populations to 0.54 between Pacific and Atlantic coasts. Genetic diversity was highest in the Pacific and lowest in the subarctic, consistent with colonization of the Arctic and Atlantic oceans from the Pacific less than 300 kya. Using redundancy analyses and two climate change projection scenarios, we found that subarctic populations are predicted to be potentially more vulnerable to climate change through genomic offset predictions. Conservation planning in Canada should thus ensure that representative populations from each identified clade are included within a national network so that latent genetic diversity is protected, and gene flow is maintained. Northern populations, in particular, may require additional mitigation measures given their potential susceptibility to a rapidly changing climate.

As climate change transforms marine environments globally, species distributions correspondingly shift to locations where conditions have become or remain favourable. The ability to model these distributional shifts has been facilitated by species distribution models (SDMs). However, current SDM approaches have largely ignored climate‐driven changes in species interactions, which ultimately can have an important influence on species distributions. In this study, we utilize a long‐term, large‐scale dataset spanning 48 years and approximately 30 degrees latitude across the Canadian Atlantic shelf. We examine how climate influences the distribution and predation patterns of two invertebrates, northern shrimp Pandalus borealis and snow crab Chionoecetes opilio, aiming to evaluate the impacts of climate change on prey distributions. We found that both invertebrate species have a pronounced predicted response to climate change, with a northern shift in the distribution of northern shrimp and an overall reduction in abundance of both snow crab and shrimp associated with warming temperatures. Including predatory interactions as predictors in the SDMs (either directly via predator densities or via estimated predation rates) improved prediction accuracy for northern shrimp but not for snow crab. This is consistent with the ecology of these two species, as northern shrimp is more vulnerable to predation than snow crab. We found that the projections of future northern shrimp distributions are sensitive to the predicted spatial distribution and abundance of predators, highlighting the inherent complexity of predicting species response to climate change. Collectively, these results contribute to a broader literature that seeks to improve the capabilities of models to predict the effects of species interactions on species distributions under changing ecological conditions. [ABSTRACT FROM AUTHOR]

Species with widespread distributions play a crucial role in our understanding of climate change impacts on population structure. In marine species, population structure is often governed by both high connectivity potential and selection across strong environmental gradients. Despite the complexity of factors influencing marine populations, studying species with broad distribution can provide valuable insights into the relative importance of these factors and the consequences of climate‐induced alterations across environmental gradients. We used the northern shrimp Pandalus borealis and its wide latitudinal distribution to identify current drivers of population structure and predict the species' vulnerability to climate change. A total of 1514 individuals sampled across 24° latitude were genotyped at high geographic (54 stations) and genetic (14,331 SNPs) resolutions to assess genetic variation and environmental correlations. Four populations were identified in addition to finer substructure associated with local adaptation. Geographic patterns of neutral population structure reflected predominant oceanographic currents, while a significant proportion of the genetic variation was associated with gradients in salinity and temperature. Adaptive landscapes generated using climate projections suggest a larger genomic offset in the southern extent of the P. borealis range, where shrimp had the largest adaptive standing genetic variation. Our genomic results combined with recent observations point to further deterioration in southern regions and an impending vulnerable status in the regions at higher latitudes for P. borealis. They also provide rare insights into the drivers of population structure and climatic vulnerability of a widespread meroplanktonic species, which is crucial to understanding future challenges associated with invertebrates essential to ecosystem functioning. [ABSTRACT FROM AUTHOR]

A global decline in seagrass populations has led to renewed calls for their conservation as important providers of biogenic and foraging habitat, shoreline stabilization and carbon storage. Eelgrass (Zostera marina) occupies the largest geographic range among seagrass species spanning a commensurately broad spectrum of environmental conditions. In Canada, eelgrass is managed as a single phylogroup despite occurring across three oceans and a range of ocean temperatures and salinity gradients. Previous research has focused on applying relatively few markers to reveal population structure of eelgrass, whereas a whole‐genome approach is warranted to investigate cryptic structure among populations inhabiting different ocean basins and localized environmental conditions. We used a pooled whole‐genome re‐sequencing approach to characterize population structure, gene flow and environmental associations of 23 eelgrass populations ranging from the Northeast United States to Atlantic, subarctic and Pacific Canada. We identified over 500,000 SNPs, which when mapped to a chromosome‐level genome assembly revealed six broad clades of eelgrass across the study area, with pairwise FST ranging from 0 among neighbouring populations to 0.54 between Pacific and Atlantic coasts. Genetic diversity was highest in the Pacific and lowest in the subarctic, consistent with colonization of the Arctic and Atlantic oceans from the Pacific less than 300 kya. Using redundancy analyses and two climate change projection scenarios, we found that subarctic populations are predicted to be potentially more vulnerable to climate change through genomic offset predictions. Conservation planning in Canada should thus ensure that representative populations from each identified clade are included within a national network so that latent genetic diversity is protected, and gene flow is maintained. Northern populations, in particular, may require additional mitigation measures given their potential susceptibility to a rapidly changing climate. [ABSTRACT FROM AUTHOR]

The Eastern Shore Islands (ESI) archipelago on the Scotian Shelf supports a rich variety of biogenic habitats and associated diversity of coastal species. The unique and complex geometry of the ESI coastline has a significant impact on circulation and, correspondingly, influences the dispersal of nearshore organisms. For many coastal areas, the ability to accurately resolve the dispersal processes is contingent on the availability of oceanographic models that can resolve fine-scale coastal boundary conditions, including coastlines and bathymetric features. We applied a high-resolution ocean circulation model and Lagrangian particle tracking in the ESI to simulate dispersal of nearshore organisms. Our results revealed predominant southwest–northeast transport that was associated with a nearshore reversal flow. While transport among different zones of the study region is mainly determined by residual currents over the long term, tidal currents dominate patterns of particle dispersal over shorter time scales. An analysis of Lagrangian coherent structures found that they were consistently associated with the mouths of bays, demonstrating that the islands and associated oceanographic processes promote self-retention. These results highlight how complex coastlines and associated oceanographic processes promote retention and underline the need to resolve these fine-scale physical and oceanographic features when estimating biophysical dispersal in the coastal environment. [ABSTRACT FROM AUTHOR]

Author(s): E. Troja (corresponding author) [1, 2]; L. Piro [3]; H. van Eerten [4]; R. T. Wollaeger [5]; M. Im [6]; O. D. Fox [7]; N. R. Butler [8]; S. [...]

The Northwest Atlantic cod stocks collapsed in the early 1990s and have yet to recover, despite the subsequent establishment of a continuing fishing moratorium. Efforts to understand the collapse and lack of recovery have so far focused mainly on the dynamics of commercially harvested species. Here, we use data from a 33-year scientific trawl survey to determine to which degree the signatures of the collapse and recovery of the cod are apparent in the spatial and temporal dynamics of the broader groundfish community. Over this 33-year period, the groundfish community experienced four phases of change: (i) a period of rapid, synchronous biomass collapse in most species, (ii) followed by a regime shift in community composition with a concomitant loss of functional diversity, (iii) followed in turn by periods of slow compositional recovery, and (iv) slow biomass growth. Our results demonstrate how a community-wide perspective can reveal new aspects of the dynamics of collapse and recovery unavailable from the analysis of individual species or a combination of a small number of species. Overall, we found evidence that such community-level signals should be useful for designing more effective management strategies to ensure the persistence of exploited marine ecosystems.

Clinal variation across replicated environmental gradients can reveal evidence of local adaptation, providing insight into the demographic and evolutionary processes that shape intraspecific diversity. Using 1773 genome-wide single nucleotide polymorphisms we evaluated latitudinal variation in allele frequency for 134 populations of North American and European Atlantic salmon (Salmo salar). We detected 84 (4.74%) and 195 (11%) loci showing clinal patterns in North America and Europe, respectively, with 12 clinal loci in common between continents. Clinal single nucleotide polymorphisms were evenly distributed across the salmon genome and logistic regression revealed significant associations with latitude and seasonal temperatures, particularly average spring temperature in both continents. Loci displaying parallel clines were associated with several metabolic and immune functions, suggesting a potential basis for climate-associated adaptive differentiation. These climate-based clines collectively suggest evidence of large-scale environmental associated differences on either side of the North Atlantic. Our results support patterns of parallel evolution on both sides of the North Atlantic, with evidence of both similar and divergent underlying genetic architecture. The identification of climate-associated genomic clines illuminates the role of selection and demographic processes on intraspecific diversity in this species and provides a context in which to evaluate the impacts of climate change.

The Biophysical and Ecological Overview of the Fundian Channel-Browns Bank Area of Interest (AOI) summarizes what is known about key physical and biological components of the Fundian Channel-Browns Bank ecosystem. These key attributes and description of their ecosystem function can be used to inform the development of Conservation Objectives and management measures, should the study area be established as a Marine Protected Area under Canada's Oceans Act. The Fundian Channel-Browns Bank is an offshore AOI that includes representative portions of the continental slope, Browns Bank, Georges Basin, the Fundian Channel, and Northeast Channel. Diverse assemblages of fishes and invertebrates are associated with the correspondingly diverse topographic features and unique oceanographic processes of the area. Significant concentrations of corals and sponges have been identified within the Northeastern Channel Coral Conservation Area and southern Browns Bank that are encompassed by the proposed boundaries. High productivity within the AOI is linked to the unique oceanographic features including upwelling and circulation gyres, as well as dynamic features of the warm Gulf Stream. The AOI encompasses an area of highly suitable habitat for juvenile Atlantic Halibut, as well as several depleted species and species at risk including Atlantic Cod (Endangered - COSEWIC), Atlantic Wolffish (Special Concern - SARA), Cusk (Endangered - COSEWIC), Spiny Dogfish (Special Concern - COSEWIC), Smooth Skate (Special Concern - COSEWIC), Thorny Skate (Special Concern - COSEWIC), and White Hake (Threatened - COSEWIC). The area also encompasses foraging habitats for cetaceans, sea turtles and large pelagic fishes such as Bluefin Tuna and Swordfish. The Fundian Channel-Browns Bank area is also noted as important foraging ground for most functional guilds of marine birds, including several species listed by SARA and the IUCN. [ABSTRACT FROM AUTHOR]

To understand coastal dispersal dynamics of Atlantic cod (Gadus morhua), we examined spatiotemporal egg and larval abundance patterns in coastal Newfoundland. In recent decades, Smith Sound, Trinity Bay has supported the largest known overwintering spawning aggregation of Atlantic cod in the region. We estimated spawning and dispersal characteristics for the Smith Sound-Trinity Bay system by fitting ichthyoplankton abundance data to environmentally-driven, simplified box models. Results show protracted spawning, with sharply increased egg production in early July, and limited dispersal from the Sound. The model for the entire spawning season indicates egg export from Smith Sound is 13%•day(-1) with a net mortality of 27%•day(-1). Eggs and larvae are consistently found in western Trinity Bay with little advection from the system. These patterns mirror particle tracking models that suggest residence times of 10-20 days, and circulation models indicating local gyres in Trinity Bay that act in concert with upwelling dynamics to retain eggs and larvae. Our results are among the first quantitative dispersal estimates from Smith Sound, linking this spawning stock to the adjacent coastal waters. These results illustrate the biophysical interplay regulating dispersal and connectivity originating from inshore spawning of coastal northwest Atlantic.