Atlantic Coast Of Canada Research Articles

Landscapes on the edge

AbstractMany landscapes are on the edge literally, particularly here on the Atlantic Coast of Canada. But landscapes everywhere are on the edge metaphorically: on the edge of change. Tackling the collective challenges we face, and redefining a “good life” in these new circumstances, will likely transform the places and landscapes that we care about. Yet change is hard and it is felt unevenly across space and social strata. We often instinctively feel that the landscapes of the present should dominate the future—an idea I've been calling “climax thinking”—but in many cases, those current landscape settings solve old problems and cause new ones. Drawing on recent empirical Atlantic research about renewable energy and coastal adaptation, this lecture explores some of the cultural shifts required to reimagine our landscapes and to meet the challenges ahead, identifying key roles for geographers along the way.

Characterization of MLST-99 Salmonella Typhimurium and the monophasic variant I:4,[5],12:i:- isolated from Canadian Atlantic coast shellfish.

Salmonella enterica subsp. enterica Typhimurium and its monophasic variant I 1;4,[5],12:i:- (MVST) are responsible for thousands of reported cases of salmonellosis each year in Canada, and countries worldwide. We investigated S. Typhimurium and MVST isolates recovered from raw shellfish harvested in Atlantic Canada by the Canadian Food Inspection Agency (CFIA) over the past decade, to assess the potential impact of these isolates on human illness and to explore possible routes of shellfish contamination. Whole-genome sequence analysis was performed on 210 isolates of S. Typhimurium and MVST recovered from various food sources, including shellfish. The objective was to identify genetic markers linked to ST-99, a sequence type specifically associated with shellfish, which could explain their high prevalence in shellfish. We also investigated the genetic similarity amongst CFIA ST-99 isolates recovered in different years and geographical locations. Finally, the study aimed to enhance the molecular serotyping of ST-99 isolates, as they are serologically classified as MVST but are frequently misidentified as S. Typhimurium through sequence analysis. To ensure recovery of ST-99 from shellfish was not due to favourable growth kinetics, we measured the growth rates of these isolates relative to other Salmonella and determined that ST-99 did not have a faster growth rate and/or shorter lag phase than other Salmonella evaluated. The CFIA ST-99 isolates from shellfish were highly clonal, with up to 81 high-quality single nucleotide variants amongst isolates. ST-99 isolates both within the CFIA collection and those isolated globally carried numerous unique deletions, insertions and mutations in genes, including some considered important for virulence, such as gene deletions in the type VI secretion system. Interestingly, several of these genetic characteristics appear to be unique to North America. Most notably was a large genomic region showing a high prevalence in genomes from Canadian isolates compared to those from the USA. Although the functions of the majority of the proteins encoded within this region remain unknown, the genes umuC and umuD, known to be protective against UV light damage, were present. While this study did not specifically examine the effects of mutations and insertions, results indicate that these isolates may be adapted to survive in specific environments, such as ocean water, where wild birds and/or animals serve as the natural hosts. Our hypothesis is reinforced by a global phylogenetic analysis, which indicates that isolates obtained from North American shellfish and wild birds are infrequently connected to isolates from human sources. These findings suggest a distinct ecological niche for ST-99, potentially indicating their specialization and adaptation to non-human hosts and environments, such as oceanic habitats.

Differences in diversity and community composition of the shell microbiome of apparently healthy lobsters Homarus americanus across Atlantic Canada.

Host-microbe dynamics are of increasing interest in marine research due to their role in host health and productivity. Changes in the shell microbiome of American lobsters have been associated with epizootic shell disease, a syndrome that is spreading northwards across the eastern U.S. and Canadian Atlantic coast. This study analyzed differences in alpha and beta diversity, as well as differentially abundant taxa, in the shell-associated bacterial community of apparently healthy lobsters from four lobster fishing areas (LFAs) in Atlantic Canada. Over 180 lobsters from New Brunswick, Nova Scotia and Prince Edward Island (PEI) were sampled during seven sampling events over four sampling months. The bacterial community was identified using novel PacBio long-read sequencing, while alpha and beta diversity parameters were analyzed using linear regression models and weighted UniFrac distances. The bacterial richness, diversity and evenness differed by sampling location, sampling month, and molt stage, but not by lobster sex or size, nor sampling depth. Similarly, based on LFA, sampling month, year and lobster molt stage, the shell microbiome differed in microbial community composition with up to 34 out of 162 taxa differing significantly in abundance between sampling groups. This large-scale microbial survey suggests that the shell microbial diversity of apparently healthy lobsters is influenced by spatial and temporal factors such as geographic location, as well as the length of time the carapace is exposed to the surrounding seawater.

Annual sea level variations off Atlantic Canada from satellite altimetry

Annual cycle of sea level off Atlantic Canada has been investigated based on a merged satellite altimetry dataset and a monthly temperature and salinity dataset. The altimetric results were compared with coastal tide-gauge data and steric height calculated from the temperature and salinity dataset. There was a general north-south variation in the amplitude of the altimetric annual cycle, increasing from 4 cm in the Labrador Sea to 15 cm in the Gulf Stream and the North Atlantic Current Region. The annual cycle in the deep ocean can approximately be accounted for by the steric height variability relative to 700 m, in which the thermosteric effect was the dominant contributor. The halosteric effect over the continental slope, especially over the northern Labrador Slope was also important. While the thermosteric effect occurred dominantly at the top 100 m water column, there was substantial halosteric variation in the 100–300 m water column. The annual sea level cycle along the Canadian Atlantic coast showed a complicated pattern in amplitude, but the phase was highly coherent with the highest sea level in fall. The steric height accounts for a substantial portion of the coastal annual cycle, but other factors such as wind forcing may be equally important.

Pseudohepatospora borealis n. gen. n. sp. (Microsporidia: Enterocytozoonida): A microsporidian pathogen of the Jonah crab (Cancer borealis)

The microsporidian diversity catalogued so far has resulted in the development of several taxonomic groups, one of which is the Enterocytozoonida – a group of generalist ‘ultimate opportunists’, which infect many fished and aquacultured animals, as well as a broad suite of host taxa, including humans. In this study, we provide phylogenetic, ultrastructural, developmental, and pathological evidence for the creation of a new genus and species to hold a microsporidian parasite of the Jonah crab, Cancer borealis.Cancer borealis represents a species of commercial interest and has become the target of a recently developed fishery on the USA and Canadian Atlantic coast. This species was found to harbour a microsporidian parasite that develops in the cytoplasm of alpha and beta cells of the hepatopancreas. We retrieved a 937 bp fragment of the parasite SSU region, alongside developmental and ultrastructural data that suggests this species is ∼ 87 % similar to Parahepatospora carcini and develops in a similar manner in direct association with the host cell cytoplasm. The mature spores are ovoid in shape and measure 1.48 ± 0.15 µm (SD) in length and 1.00 ± 0.11 µm (SD) in width.Phylogenetically, the new parasite clades in the Enterocytozoonida on the same branch as P. carcini. We provide a new genus and species to hold the parasite: Pseudohepatospora borealis n. gen. n. sp. (Microsporidia: Enterocytozoonida) and explore the likelihood that this species may fit into the Hepatoporidae family.

Pathogenic variants carrier screening in New Brunswick: Acadians reveal high carrier frequency for multiple genetic disorders

BackgroundFounder populations that have recently undergone important genetic bottlenecks such as French-Canadians and Ashkenazi Jews can harbor some pathogenic variants at a higher carrier rate than the general population, putting them at a higher risk for certain genetic diseases. In these populations, there can be considerable benefit to performing ethnic-based or expanded preconception carrier screening, which can help in the prevention or early diagnosis and management of some genetic diseases. Acadians are descendants of French immigrants who settled in the Atlantic Coast of Canada in the seventeenth century. Yet, the Acadian population has never been investigated for the prevalence/frequency of disease-causing genetic variants.MethodsAn exome sequencing panel for 312 autosomal recessive and 30 X-linked diseases was designed and specimens from 60 healthy participants were sequenced to assess carrier frequency for the targeted diseases.ResultsIn this study, we show that a sample population of Acadians in South-East New Brunswick harbor variants for 28 autosomal recessive and 1 X-linked diseases, some of which are significantly more frequent in comparison to reference populations.ConclusionResults from this pilot study suggests a need for further investigation of genomic variation in this population and possibly implementation of targeted carrier and neonatal screening programs.

Characterizing Atmospheric Aerosols off the Atlantic Canadian Coast During C-FOG

Characterizing Atmospheric Aerosols off the Atlantic Canadian Coast During C-FOG

Microphysics of aerosol, fog and droplet residuals on the Canadian Atlantic coast

Fog has a wide range of impacts that can include transportation disruptions and climate effects. Despite being a common phenomenon, models struggle to incorporate fog microphysical properties which can affect the visibility, formation and dissipation of fog. Results are presented from a fog microphysics study conducted in June and July of 2016 near Halifax, on the eastern coast of Canada, where droplet and aerosol size distributions were measured, as well as fog droplet residuals using a ground-based counterflow virtual impactor. In the ten distinct events that were analyzed, fog never formed when the dew-point temperature was lower than the sea-surface temperature, suggesting that advection fog was primarily observed. During fog events, the concentration of particles larger than 500 nm in diameter was observed to decrease up to 90%, suggesting that nucleation scavenging was an important loss process during fog. Maximum droplet concentration was correlated (r = 0.61) to the total pre-fog aerosol concentration, despite a large (423 nm) estimated activation diameter. From our measurements, the peak supersaturation (SS) was estimated to range from 0.015–0.046%, including uncertainties due to chemical composition, which is lower than previous estimates for continental fog, including mountain sites, and would be consistent with advection fog as well as the presence of sea salt aerosol. Using basic assumptions, we estimate that for each added aerosol per cm3 in the air mass, the maximum fog droplet concentration increases by 0.011 per cm3 and the fog albedo increases by (0.55–3.8) × 10−4. This in-situ dataset will help evaluate models to ultimately improve fog forecasts for coastal areas and further our understanding of aerosol-cloud interactions.

The Hidden Biodiversity of Intertidal Mussel Beds under contrasting Wave Exposures

Photo 1: Intertidal mussel bed from the Atlantic coast of Nova Scotia, Canada, viewed at low tide. Photo credit: Ricardo A. Scrosati. This photograph illustrates the article “Abundance data for invertebrate assemblages from intertidal mussel beds along the Atlantic Canadian coast” published by Ricardo A. Scrosati, Lorena P. Arribas, and Luigia Donnarumma in Ecology. https://doi.org/10.1002/ecy.3137

The Subhabitat Dependence of Biogeographic Pattern

We introduce and test the subhabitat dependence hypothesis (SDH) in biogeography. This hypothesis posits that biogeographic pattern within a region differs when determined with species abundance data from different subhabitat types. It stems from the notion that the main abiotic factors that drive species distribution in different subhabitat types across a biogeographic region often vary differently across space. To test the SDH, we measured the abundance of algae and sessile invertebrates in two different subhabitats (high intertidal zone and mid-intertidal zone) at eight locations along the Atlantic Canadian coast. We conducted multivariate analyses of the species abundance data to compare alongshore biogeographic pattern between both zones. For both subhabitat types, location groupings based on community similarity not always responded to geographic proximity, leading to biogeographic patchiness to some extent. Nonetheless, both biogeographic patterns were statistically unrelated, thus supporting the SDH. This lack of concordance was most evident for southern locations, which clustered together based on high-intertidal data but showed considerable alongshore patchiness based on mid-intertidal data. We also found that the ordination pattern of these eight locations based on sea surface temperature data was significantly related to biogeographic pattern for the mid-intertidal zone but not for the high intertidal zone. This finding supports the rationale behind the SDH due to the longer periods of submergence experienced by the mid-intertidal zone. Overall, we conclude that biogeographic pattern within a region can depend on the surveyed subhabitat type. Thus, biological surveys restricted to specific subhabitats may not properly reveal biogeographic pattern for a biota as a whole or even just for other subhabitats. As many studies generate biogeographic information with data only for specific subhabitats, we recommend testing the SDH in other systems to determine its domain of application.

Half-hourly changes in intertidal temperature at nine wave-exposed locations along the Atlantic Canadian coast: a 5.5-year study

Abstract. Intertidal habitats are unique because they spend alternating periods of submergence (at high tide) and emergence (at low tide) every day. Thus, intertidal temperature is mainly driven by sea surface temperature (SST) during high tides and by air temperature during low tides. Because of that, the switch from high to low tides and vice versa can determine rapid changes in intertidal thermal conditions. On cold-temperate shores, which are characterized by cold winters and warm summers, intertidal thermal conditions can also change considerably with seasons. Despite this uniqueness, knowledge on intertidal temperature dynamics is more limited than for open seas. This is especially true for wave-exposed intertidal habitats, which, in addition to the unique properties described above, are also characterized by wave splash being able to moderate intertidal thermal extremes during low tides. To address this knowledge gap, we measured temperature every half hour during a period of 5.5 years (2014–2019) at nine wave-exposed rocky intertidal locations spanning 415 km of the Atlantic coast of Nova Scotia, Canada. This data set is freely available from the figshare online repository (Scrosati and Ellrich, 2020a; https://doi.org/10.6084/m9.figshare.12462065.v1). We summarize the main properties of this data set by focusing on location-wise values of daily maximum and minimum temperature and daily SST, which we make freely available as a separate data set in figshare (Scrosati et al., 2020; https://doi.org/10.6084/m9.figshare.12453374.v1). Overall, this cold-temperate coast exhibited a wide annual SST range, from a lowest overall value of −1.8 ∘C in winter to a highest overall value of 22.8 ∘C in summer. In addition, the latitudinal SST trend along this coast experienced a reversal from winter (when SST increased southwards) to summer (when SST decreased southwards), seemingly driven by alongshore differences in summer coastal upwelling. Daily temperature maxima and minima were more extreme, as expected from their occurrence during low tides, ranging from a lowest overall value of −16.3 ∘C in winter to a highest overall value of 41.2 ∘C in summer. Daily maximum temperature in summer varied little along the coast, while daily minimum temperature in winter increased southwards. This data set is the first of its kind for the Atlantic Canadian coast and exemplifies in detail how intertidal temperature varies in wave-exposed environments on a cold-temperate coast.

Abundance data for invertebrate assemblages from intertidal mussel beds along the Atlantic Canadian coast.

This data set describes the abundance of 50 invertebrate taxa found in intertidal mussel beds along the Atlantic Canadian coast. This information resulted from a regional-scale study that investigated the effects of wave exposure on the richness and composition of invertebrate assemblages from intertidal mussel beds. Abundance data are provided for taxa representing the Annelida, Arthropoda, Bryozoa, Chordata, Cnidaria, Echinodermata, Mollusca, Nematoda, Nemertea, and Platyhelminthes. The data characterize mussel beds from wave-sheltered and wave-exposed locations spanning 315 km of the coast of Nova Scotia. Univariate and multivariate analyses revealed that the compositional structure of these invertebrate assemblages differed markedly depending on wave exposure. Overall, because of its taxonomic diversity, the inclusion of data for basal, intermediate, and top trophic levels, and the coverage of two extremes of environmental stress, this data set could be useful to test broader aspects of ecological theory. Areas of ecology that could advance using this data set are those concerning environmental stress models of community organization, abundance-occupancy relationships, species co-occurrence, species abundance distributions, dominance and rarity, spatial scales of population and community variation, and distribution of functional and phylogenetic diversity. Use of this data set for academic or educational purposes is allowed as long as the data source is properly cited. When used for academic or educational purposes, this data set should be cited using the title of this Data Paper, the names of the authors, the year of publication, and the corresponding volume and article numbers.

Effects of Intertidal Elevation on Barnacle Recruit Density and Size in Wave-Exposed Habitats on the Atlantic Canadian Coast

Barnacle recruitment is often studied in rocky intertidal habitats due to the relevant role that barnacles can play in intertidal communities. In 2014, recruitment of the barnacle Semibalanus balanoides was measured at high elevations in wave-exposed intertidal habitats on the NW Atlantic coast in Nova Scotia, Canada. Values were considerably lower than previously reported for middle elevations in wave-exposed intertidal habitats on the NE Atlantic and NE Pacific coasts. To determine if such differences in recruitment may have resulted from elevation influences, I did a field experiment in 2019 in wave-exposed intertidal habitats in Nova Scotia to test the hypothesis that recruitment is higher at middle than at high elevations, based on known environmental differences between both elevation zones. Based on data from 3 locations spanning 158 km of the Atlantic coast of Nova Scotia, barnacle recruitment was, on average, nearly 200% higher (and recruits were larger) at middle than at high elevations. However, even with this increase, barnacle recruitment on this NW Atlantic coast is still lower than for comparable habitats on the NE Atlantic and NE Pacific coasts, and also lower than previously reported for wave-exposed locations farther south on the NW Atlantic coast, in Maine, USA. Therefore, barnacle recruitment in wave-exposed intertidal habitats on the Atlantic coast of Nova Scotia is moderate relative to other shores. This difference in the supply of barnacle recruits might influence the intensity of interspecific interactions involving barnacles.

Upwelling spike and marked SST drop after the arrival of cyclone Dorian to the Atlantic Canadian coast

In intertidal environments, temperature changes at hourly scales are ecologically relevant because of the physiological stress that organisms must endure as a result. Tides constitute the main source of such changes, as low tides periodically expose intertidal habitats to aerial conditions, which can exhibit extreme high and low temperatures in summer and winter, respectively. This study identifies a source of strong hourly thermal variation that acts upon seawater temperature. Hours after the arrival of cyclone Dorian to the Atlantic Canadian coast in September 2019, intertidal loggers revealed that sea surface temperature (SST) decreased by 10–12 °C. Online data indicated that neither tidal amplitude nor air temperature were responsible for this marked SST drop. Conversely, data on wind speed and direction strongly suggest that a pronounced spike in coastal upwelling caused by this cyclone drove the sharp drop in intertidal SST. Bakun's upwelling index, for instance, peaked at 689 m3 s−1 (100 m of coastline)−1 a few hours after Dorian's landfall. It remains to be seen how this marked SST drop may have affected intertidal organisms, as they were then acclimated to summer conditions. As the frequency and intensity of cyclones are predicted to increase with climate change in temperate latitudes, cyclone-related intertidal thermal ecology might deserve further attention.

Morphological and molecular assessment of large sea anemones (Actiniaria: Actiniidae) in Newfoundland (eastern Canada)

Literature records of large actiniid sea anemones along the Atlantic coast of Canada currently include three Urticina species: U. felina, U. fecunda and U. crassicornis. The findings of the present morphological and molecular study conducted in eastern Newfoundland suggest that U. felina is often misidentified, and that this region may only harbor two similar-looking species: U. crassicornis and Cribrinopsis similis. The latter were identified using genetic analysis and comparison of key characters with the same species collected from other regions of the North Atlantic (Barents Sea), whereas no specimen corresponding to U. felina was found. Mitochondrial gene sequences of U. crassicornis, U. felina and C. similis were identical except for a different haplotype found in several specimens of U. crassicornis (with one nucleotide substitution), in contrast to five nucleotide insertions in 16S rRNA fragments of U. fecunda. Phylogenetic analysis based on three mitochondrial and two nuclear gene fragments revealed that the most closely related species among the above-mentioned were U. crassicornis and U. felina, nevertheless U. fecunda groups in the same clade as the Urticina species.

Marked contrast in wind-driven upwelling on the southeastern Nova Scotia coast in July of two years differing in ENSO conditions

Abstract Upwelling occurs on several coasts of the world, but it has mostly been studied on eastern ocean boundaries. We investigated upwelling on a western ocean boundary for which limited information exists. Using daily in-situ data on sea surface temperature (SST), we found a marked contrast in coastal cooling between July 2014 (pronounced) and July 2015 (weak) at two locations 110 km apart on the Atlantic coast of Nova Scotia, Canada. These findings are consistent with a marked interannual difference in wind-driven upwelling. On the one hand, southwesterlies (which cause upwelling on this coast) were more frequent in July 2014 than in July 2015. On the other hand, Bakun’s upwelling index (which is based on wind data and geographic information) indicated that coastal upwelling was more common and intense in July 2014 than in July 2015, while the reverse was true for downwelling. Interestingly, a strong El Niño event occurred in July 2015, while no El Niño (or La Niña) conditions happened in July 2014. In a recent book evaluating upwelling systems around the world, the system that is the focus of the present study was not included. Therefore, our findings should stimulate future research on upwelling on the Atlantic Canadian coast, in that way helping to further develop the knowledge base for western ocean boundaries.

Predicting extreme surges from sparse data using a copula‐based hierarchical Bayesian spatial model

AbstractA hierarchical Bayesian model is proposed to quantify the magnitude of extreme surges on the Atlantic coast of Canada with limited data. Generalized extreme value distributions are fitted to surges derived from water levels measured at 21 buoys along the coast. The parameters of these distributions are linked together through a Gaussian field whose mean and variance are driven by atmospheric sea‐level pressure and the distance between stations, respectively. This allows for information sharing across the original stations and for interpolation anywhere along the coast. The use of a copula at the data level of the hierarchy further accounts for the dependence between locations, allowing for inference beyond a site‐by‐site basis. It is shown how the extreme surges derived from the model can be combined with the tidal process to predict potentially catastrophic water levels.

Assessment of recreational boating as a vector for marine non-indigenous species on the Atlantic coast of Canada

We developed a new predictive approach to evaluate the relative invasion hazard posed by recreational boats as vectors for non-indigenous species (NIS) in marine ecoregions on the Atlantic coast of Canada. It combines data from behavioral boater questionnaires, surveys of boat macrofouling, and an extensive NIS monitoring program in marinas. The relative invasion hazard posed by boats in nine marine ecoregions was estimated by combining information on NIS infestation levels in source ecoregions, the probability that boats will be fouled, boat movements and environmental similarity between source and receiving marinas, and estimates of annual recreational traffic within and between ecoregions. A total of 52.1% of surveyed boats had macrofouling on hull or niche areas, suggesting a high potential for NIS transport. High-risk boats were those that had spent extended periods in water, traveled extensively from invaded locations, and received little maintenance. Further, the high degree of connectivity between and within ecoregions, and high survival probabilities of NIS, highlight the threat of NIS introduction and spread via recreational boating in Atlantic Canadian waters. Of all Atlantic Canadian ecoregions, the Scotian Shelf ecoregion was classified as having the “Highest” Final Hazard score. However, boats with Intermediate to Highest scores travel to most ecoregions, underlining the importance of this vector to the introduction and spread of NIS in Atlantic Canadian coast. A simulated out-of-water cleaning after 3 months reduced the hazard in ecoregions with greater scores.

A 5-year study (2014–2018) of the relationship between coastal phytoplankton abundance and intertidal barnacle size along the Atlantic Canadian coast

Benthic–pelagic coupling refers to the ecological relationships between benthic and pelagic environments. Studying such links is particularly useful to understand biological variation in intertidal organisms along marine coasts. Filter-feeding invertebrates are ecologically important on marine rocky shores, so they have often been used to investigate benthic–pelagic coupling. Most studies, however, have been conducted on eastern ocean boundaries. To evaluate benthic–pelagic coupling on a western ocean boundary, we conducted a 5-year study spanning 415 km of the Atlantic coast of Nova Scotia (Canada). We hypothesized that the summer size of intertidal barnacles (Semibalanus balanoides) recruited in the preceding spring would be positively related to the nearshore abundance (biomass) of phytoplankton, as phytoplankton constitutes food for the nauplius larvae and benthic stages of barnacles. Every year between 2014 and 2018, we measured summer barnacle size in clearings created before spring recruitment on the rocky substrate at eight wave-exposed locations along this coast. We then examined the annual relationships between barnacle size and chlorophyll-a concentration (Chl-a), a proxy for phytoplankton biomass. For every year and location, we used satellite data to calculate Chl-a averages for a period ranging from the early spring (when most barnacle larvae were in the water) to the summer (when barnacle size was measured after weeks of growth following spring benthic recruitment). The relationships were always positive, Chl-a explaining nearly half, or more, of the variation in barnacle size in four of the five studied years. These are remarkable results because they were based on a relatively limited number of locations (which often curtails statistical power) and point to the relevance of pelagic food supply to explain variation in intertidal barnacle size along this western ocean boundary coast.

Seascape genomics of eastern oyster (Crassostrea virginica) along the Atlantic coast of Canada.

Interactions between environmental factors and complex life‐history characteristics of marine organisms produce the genetic diversity and structure observed within species. Our main goal was to test for genetic differentiation among eastern oyster populations from the coastal region of Canadian Maritimes against expected genetic homogeneity caused by historical events, taking into account spatial and environmental (temperature, salinity, turbidity) variation. This was achieved by genotyping 486 individuals originating from 13 locations using RADSeq. A total of 11,321 filtered SNPs were used in a combination of population genomics and environmental association analyses. We revealed significant neutral genetic differentiation (mean F ST = 0.009) between sampling locations, and the occurrence of six major genetic clusters within the studied system. Redundancy analyses (RDAs) revealed that spatial and environmental variables explained 3.1% and 4.9% of the neutral genetic variation and 38.6% and 12.2% of the putatively adaptive genetic variation, respectively. These results indicate that these environmental factors play a role in the distribution of both neutral and putatively adaptive genetic diversity in the system. Moreover, polygenic selection was suggested by genotype–environment association analysis and significant correlations between additive polygenic scores and temperature and salinity. We discuss our results in the context of their conservation and management implications for the eastern oyster.