Effects of Climate-Responsive, Fjordscape, and Aquaculture-Associated Environmental Drivers on Fjord Hyperbenthic Community Structure

Abstract

Marine community sensitivity to climate change can be informed by examining community patterns along current environmental gradients. Fjords provide natural laboratories for such studies due to their variable oceanographic conditions that can differ from basin to basin. Bottom trawl samples were collected from 17 fjord basins and nearshore coastal stations (59–63°N) from 2011 to 2022. We examined how climate-responsive (temperature, salinity, and oxygen) and fixed environmental variables (bottom depth, sill depth, and distance to coastline) as well as aquaculture impact score (calculated using biomass capacity within a 5 km radius) correlate with differences in hyperbenthic community biomass, diversity, and composition. We focused on fish and crustacean species composition, diversity, and biomass as well as the biomass and distribution of a recently proliferating jellyfish, Periphylla periphylla. Our results indicate that fixed environmental variables (e.g., bottom depth and sill depth) are important predictors of community biodiversity; biodiversity decreased with bottom depth and was highest in fjord basins with 151–250 m deep sills. Fish and crustacean biomass was negatively correlated with distance to coastline. Four community-types were identified which separated mainly by depth, geographic location (fjord or coastal), and presence of P. periphylla. We found limited evidence of climate-responsive or aquaculture-associated drivers being strong predictors of hyperbenthic community differences. The exception was that P. periphylla biomass was negatively correlated with temperature. Oxygen was not a significant predictor of any community patterns. Since West-Norwegian fjord species are common to the N. Atlantic, the study offers broader insights into community sensitivity to environmental change.