Prediction of Changes in Arctic Benthic Ecosystems on the Basis of Large Scale Study of Benthic Biomass Size Spectra

Body size is a fundamental biological unit that is closely coupled to key ecological properties and processes. Decline in organisms’ body-size has been predicted to be “the third universal response to global warming” (alongside changes in phenology and distribution of species) in both aquatic and terrestrial systems. Some result from pelagic studies (of zooplankton and ichthyofauna) support that hypothesis. Increasing temperature results in higher abundance of smaller organisms, associated with warmer water masses or in higher proportion of juveniles vs. adults. As climate change is most dramatic at the polar regions, we aimed to present the first assessment of Benthic Biomass Size Spectra (BBSS) in both Arctic and lower latitude locations to determine possible future effects of global warming on Arctic benthic ecosystems. The study was conducted in 6 Norwegian fiords representing a wide geographical range - from 60°N up to 80°N (Raunefjorden, Balsfjorden, Ullsfjorden, Hornsund fjord, Kongsfjorden and Rijpfjorden). We hypothesize that decreasing temperature along the latitudinal gradient is reflected in organism size, here analyzed at the community level. At each location we collected three macrobenthic samples using van Veen grab, acquired hydrological settings, and collected sediments for geochemical analyses (grain size, organic matter descriptors). All macrobenthic organisms were identified and measured using microscope-based Image Analyses System. Using volumetric formulas we calculated the biovolume of each organism. For each location we plotted the BBSS. Individual biomass values were used to estimate the secondary production. The variability in size structures and functioning (production) of the studied communities were related to the environmental settings. The results are used to predict the possible effects climate warming related environmental changes on the benthic communities in Arctic coastal waters.