Boreal marine fauna from the Barents Sea disperse to Arctic Northeast Greenland

Abstract

As a result of ocean warming, the species composition of the Arctic seas has begun to shift in a boreal direction. One ecosystem prone to fauna shifts is the Northeast Greenland shelf. The dispersal route taken by boreal fauna to this area is, however, not known. This knowledge is essential to predict to what extent boreal biota will colonise Arctic habitats. Using population genetics, we show that Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella), and deep-sea shrimp (Pandalus borealis) recently found on the Northeast Greenland shelf originate from the Barents Sea, and suggest that pelagic offspring were dispersed via advection across the Fram Strait. Our results indicate that boreal invasions of Arctic habitats can be driven by advection, and that the fauna of the Barents Sea can project into adjacent habitats with the potential to colonise putatively isolated Arctic ecosystems such as Northeast Greenland.

Figure 1

Stations (green full circles) of observation for Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella) and deep-sea shrimp (Pandalus borealis) (Methods, Table 1). Arrows indicate ocean currents (Source^,). Atlantic surface currents (red arrows): IMC (Irminger Current), NAC (Norwegian Atlantic Current), WSC (West Spitsbergen Current), RAC (Return Atlantic Current). Atlantic sub-surface water (white arrows). Arctic surface currents (blue arrows): EGC (East Greenland Current), JMC (Jan Mayen Current). Arrow size indicates velocity. Map created using ESRI ArcMap (v. 10.6, www.arcgis.com).

Figure 2

Genetic evidence of Atlantic cod (Gadus morhua) (a–c), beaked redfish (Sebastes mentella) (d–f) and deep-sea shrimp (Pandalus borealis) (g–i) specimens found off Northeast Greenland originating from the Barents Sea. Maps (a,d,g) show species known distribution extent (shaded colours) in the Northeast Atlantic, catch sites of individuals in Northeast Greenland (NEG) waters (full circles), reference samples (hollow circles) and a proposed dispersal route (arrow). DAPC scatterplots (b,e,h) show how the NEG groups relate to the reference populations of the Northeast Atlantic Ocean. DAPC cluster ellipses were set to contain 95% of genotypes. DAPC scatterplots explain 94% (b), 92% (e) and 97% (h) of the total variation observed. STRUCTURE barplots (c,f,i) show membership probabilities (q) for NEG individuals based on the reference populations used. Maps were created using ESRI ArcMap (v. 10.6, www.arcgis.com).

Figure 3

Neighbour-joining trees utilising Nei’s distance, for beaked redfish (Sebastes mentella) (a) and deep-sea shrimp (Pandalus borealis) (b) Northeast Greenland groups and reference populations. Bootstrap values (>88% and >73%) on both trees suggest good reproducibility.