Oceanographic influence on the early life-history stages of benthic invertebrates during the polar night

Recent research has illuminated biological processes taking place during the polar night in the high Arctic, while simultaneously, the polar regions are undergoing rapid climate-driven change. There is a pressing need for research to establish baseline conditions and understand the influence of oceanographic factors on polar communities. We collected plankton samples in Kongsfjorden (Svalbard, Arctic) in January 2020, in order to study the early life-history stages of benthic invertebrates during the polar night. Specimens were identified using morphology and DNA barcoding. During our field campaign, a strong wind event occurred, which caused upwelling of Arctic water in the fjord. Therefore, we also investigated the influence of oceanographic factors on benthic invertebrate larvae, including temperature, salinity, and depth. Our samples included 19 different species or morphotypes belonging to ten invertebrate phyla, including three embryo morphotypes. The collection of embryos indicates that at least some taxa are reproducing in the polar night. Larval community structure at shallow stations was significantly different before and after the upwelling event. Our samples also reflected patchiness in the larval community and a significant influence of depth. The most common nutrition mode among the larval taxa we collected was lecithotrophy (energy derived from maternal yolk), but we also collected a few taxa that may be planktotrophic (feeding). Development via lecithotrophy could increase larval survival and settlement success in the low-food environment of the Arctic winter. This study provides essential data on the early life-history stages of benthic invertebrates in an understudied season.