Jon Albretsen

Genetically distinct populations of northern shrimp, Pandalus borealis , in the North Atlantic: adaptation to different temperatures as an isolation factor

The large‐scale population genetic structure of northern shrimp, Pandalus borealis, was investigated over the species’ range in the North Atlantic, identifying multiple genetically distinct groups. Genetic divergence among sample localities varied among 10 microsatellite loci (range: FST = −0.0002 to 0.0475) with a highly significant average (FST = 0.0149; P < 0.0001). In contrast, little or no genetic differences were observed among temporal replicates from the same localities (FST = 0.0004; P = 0.33). Spatial genetic patterns were compared to geographic distances, patterns of larval drift obtained through oceanographic modelling, and temperature differences, within a multiple linear regression framework. The best‐fit model included all three factors and explained approximately 29% of all spatial genetic divergence. However, geographic distance and larval drift alone had only minor effects (2.5–4.7%) on large‐scale genetic differentiation patterns, whereas bottom temperature differences explained most (26%). Larval drift was found to promote genetic homogeneity in parts of the study area with strong currents, but appeared ineffective across large temperature gradients. These findings highlight the breakdown of gene flow in a species with a long pelagic larval phase (up to 3 months) and indicate a role for local adaptation to temperature conditions in promoting evolutionary diversification and speciation in the marine environment.

Climate Change and Genetic Structure of Leading Edge and Rear End Populations in a Northwards Shifting Marine Fish Species, the Corkwing Wrasse (Symphodus melops)

One mechanism by which marine organisms may respond to climate shifts is range shifts. The corkwing wrasse (Symphodus melops) is a temperate fish species, inhabiting the coasts of Europe, that show strong indications of current as well as historical (ice-age) range shifts towards the north. Nine neutral microsatellite DNA markers were screened to study genetic signatures and spatial population structure over the entire geographic and thermal gradient of the species from Portugal to Norway. A major genetic break (F ST u200a=u200a0.159 average among pairs) was identified between Scandinavian and more southern populations, with a marked reduction (30% or more) in levels of genetic variability in Scandinavia. The break is probably related to bottleneck(s) associated with post-glacial colonization of the Scandinavian coasts, and indicates a lack of present gene flow across the North Sea. The lack of gene flow can most likely be attributed to the species’ need for rocky substrate for nesting and a relatively short pelagic larval phase, limiting dispersal by ocean currents. These findings demonstrate that long-distance dispersal may be severely limited in the corkwing wrasse, and that successful range-shifts following present climate change may be problematic for this and other species with limited dispersal abilities, even in the seemingly continuous marine environment.

Temperature-associated habitat selection in a cold-water marine fish.

Habitat selection is a complex process, which involves behavioural decisions guided by the multiple needs and constraints faced by individuals. Climate-induced changes in environmental conditions may alter those trade-offs and resulting habitat use patterns. In this study, we investigated the effect of sea temperature on habitat selection and habitat use of acoustically tagged Atlantic cod (Gadus morhua) at the Norwegian Skagerrak coast. Significant relationships between ocean temperature and habitat selection and use were found. Under favourable sea temperature thresholds (<16xa0°C), cod selected vegetated habitats, such as eelgrass and macroalgae beds, available in shallow areas. Selection for those habitats was especially high at night, when cod tended to ascend to shallower areas, presumably to feed. Selection and use of those habitats decreased significantly as temperature rose. Under increased sea surface temperature conditions, cod were absent from vegetated shallow habitats, both during the day and night, and selected instead non-vegetated rocky bottoms and sand habitats, available in deeper, colder areas. This study shows the dynamic nature of habitat selection and strongly suggests that cod in this region have to trade off food availability against favourable temperature conditions. Future increases in ocean temperature are expected to further influence the spatial behaviour of marine fish, potentially affecting individual fitness and population dynamics.

Summer mortalities and detection of ostreid herpesvirus microvariant in Pacific oyster Crassostrea gigas in Sweden and Norway

The Pacific oyster Crassostrea gigas has recently expanded its range in Scandinavia. The expansion is presumably a result of northwards larval drift. Massive settlements were recorded in many areas along the Swedish west coast and southern Norway in 2013 and 2014. After the spawning season in 2014, the temperature of the surface water peaked at 24-26°C. After this period, high and sudden mortalities occurred in a Swedish hatchery and in wild populations along the Swedish west coast and south coast of Norway. Surveys and collected data showed that mortalities mainly occurred during 3 wk in September. All size classes were affected, and affected populations displayed a patchy distribution with heavily affected and unaffected populations in close proximity. Flat oysters Ostrea edulis and blue mussels Mytilus edulis were unaffected. Ostreid herpesvirus (OsHV) was detected in moribund Pacific oyster spat as well as in surviving adults. The virus was identified as OsHV-1 μvar. This is the first detection of this variant in Scandinavia, showing that OsHV-1 μvar is present in areas with recent establishments of Pacific oysters, and where there is no aquaculture of this species.

Genetic analysis of goldsinny wrasse reveals evolutionary insights into population connectivity and potentialevidence of inadverent translocationvia aquaculture.

Eeva Jansson*, Mar ıa Quintela, Geir Dahle, Jon Albretsen, Halvor Knutsen, Carl André, Åsa Strand, Stein Mortensen, John B. Taggart, Egil Karlsbakk, Bjørn Olav Kvamme, and Kevin A. Glover Institute of Marine Research, PO Box 1870 Nordnes, 5817 Bergen, Norway Institute of Marine Research Flødevigen, 4817 His, Norway Centre for Coastal Research, University of Agder, 4604 Kristiansand, Norway Department of Marine Sciences-Tj€arnö, University of Gothenburg, 45296 Strömstad, Sweden School of Natural Sciences, Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK Institute of Biology, University of Bergen, PO Box 7803, 5020 Bergen, Norway

Climate change opens new frontiers for marine species in the Arctic: current trends and future invasion risks

Abstract Climate change and increased anthropogenic activities are expected to elevate the potential of introducing nonindigenous species (NIS) into the Arctic. Yet, the knowledge base needed to identify gaps and priorities for NIS research and management is limited. Here, we reviewed primary introduction events to each ecoregion of the marine Arctic realm to identify temporal and spatial patterns, likely source regions of NIS, and the putative introduction pathways. We included 54 introduction events representing 34 unique NIS. The rate of NIS discovery ranged from zero to four species per year between 1960 and 2015. The Iceland Shelf had the greatest number of introduction events (n = 14), followed by the Barents Sea (n = 11), and the Norwegian Sea (n = 11). Sixteen of the 54 introduction records had no known origins. The majority of those with known source regions were attributed to the Northeast Atlantic and the Northwest Pacific, 19 and 14 records, respectively. Some introduction events were attributed to multiple possible pathways. For these introductions, vessels transferred the greatest number of aquatic NIS (39%) to the Arctic, followed by natural spread (30%) and aquaculture activities (25%). Similar trends were found for introductions attributed to a single pathway. The phyla Arthropoda and Ochrophyta had the highest number of recorded introduction events, with 19 and 12 records, respectively. Recommendations including vector management, horizon scanning, early detection, rapid response, and a pan‐Arctic biodiversity inventory are considered in this paper. Our study provides a comprehensive record of primary introductions of NIS for marine environments in the circumpolar Arctic and identifies knowledge gaps and opportunities for NIS research and management. Ecosystems worldwide will face dramatic changes in the coming decades due to global change. Our findings contribute to the knowledge base needed to address two aspects of global change—invasive species and climate change.