Recruitment dynamics of Hiatella arctica within a high Arctic site (Young Sound Fjord, NE Greenland)

Abstract

Abstract Recruitment dynamics including what determines success or failure of Arctic benthic invertebrates are poorly known despite their important role for population dynamics. The main objective of this study was to assess the potential influence of extreme seasonal/physical constraints, in particular freshwater discharge, on the recruitment of a dominant bivalve Hiatella arctica within a High Arctic fjord. We collected young recruits over several sampling periods from 2016 to 2018 at two contrasting sites (inner vs middle fjord) for 5-weeks to 12-months and measured their abundance, size at metamorphosis and lipid class composition. Young stages of H. arctica settled from June to the end of October, when trophic conditions are optimal. We hypothesize that growth stops during winter due to poor trophic conditions. Data suggest that abundance of recruits, their total lipid concentration and composition of lipid classes are similar in both sites. By contrast, analyses of size-class show differing temporal and spatial patterns with 6 cohorts detected in middle fjord and only one at the inner station, which can be attributed to discrete spawning events and possible secondary migration. Based on an assessment of their potential age, we hypothesize that spat batches recruiting earlier in the summer exhibit better growth performance probably because of higher food quality and availability.