Seasonality of bivalve larvae within a high Arctic fjord

The temporal and spatial distribution of larval plankton of high latitudes is poorly understood. The objective of this work is to identify the occurrence and abundance of pelagic bivalve larvae within a high Arctic fjord(Adventfjorden, Svalbard) and to reveal their seasonal dynamics in relation to environmental variables—temperature, salinity and chlorophyll a—between December 2011 and January 2013. We applied a combination of DNA barcodingof mitochondrial 16S ribosomal RNAand morphological analysisto identify the bivalve larvae found within the plankton and demonstrate a strong seasonality in the occurrence of bivalve larvae, largely coinciding with periods of primary productivity. Seasonal occurrences of bivalve larval species differ from those known for other populations across species’ biogeographic distribution ranges. Serripes groenlandicus, which is of circum-Arctic distribution, demonstrated a later occurrence than Mya truncataor Hiatella arctica, which are of predominantly boreal or cosmopolitan distribution, respectively. S. groenlandicus larvae demonstrate the most pronounced response to seasonality, with the shortest presence in the water column. Establishing latitudinal differences in the occurrence of bivalve larvae enhances our understanding of how reproductive traits of marine invertebratesmay respond to climate-driven seasonal shifts in the occurrence of primary productivity.