Sympagic-pelagic-benthic coupling in Arctic and Atlantic waters around Svalbard revealed by stable isotopic and fatty acid tracers

Abstract

Stable isotope and fatty acid trophic markers (FATMs) were used to assess carbon flow and trophic structures of sympagic, pelagic and benthic communities in high-Arctic Svalbard. Three regions were sampled: Northwest Svalbard – dominated by Atlantic water (AtW) and limited seasonal sea ice; Northern Svalbard – dominated by AtW and perennial sea ice; and Northeast Svalbard – dominated by Arctic water (ArW) and extensive seasonal sea ice. Three to four trophic levels (TL) were found in the three habitats, with a dominance of omnivores (TL = 2.4–2.7). Ice fauna relied on phytoplankton and ice algae, zooplankton primarily on phytoplankton, while benthos relied on ice algae/refractory material. Ice fauna (mean 39%; range 17–62%) and benthos (mean 25%; range 11–65%) had high proportions of diatom-FATMs, while zooplankton had equally high diatom- and Phaeocystis/dinoflagellate-FATMs (mean 11% and 15%, respectively). Calanus-FATMs were prominent in carnivorous ice fauna (up to 28%) and zooplankton (up to 38%), but also in benthic invertebrates (up to 41%). Ice fauna biomass was low. Biomass of zooplankton and benthic infauna were variable, but positively correlated to each other (r 2=0.89; p<0.01) and sedimentary pigment concentrations (r 2>0.40; p<0.05). The coinciding peak biomasses of zooplankton and benthos in Northeast Svalbard can be explained by allochthonous organic matter of ice algal origin and highly specialized Arctic zooplankton utilizing both ice algae and phytoplankton carbon sources.