The substantial loss of Arctic sea ice will alter marine ecosystems in many ways. Recent studies have reported a distributional shift in benthic macrofaunal biomass in the Pacific Arctic, likely caused by changes in food availability for benthic organisms. Here, we assessed the influence of differences in post-bloom supply of phytoplankton to the sediment on the growth of a common Pacific Arctic bivalve (Macoma calcarea) based on field and satellite observations, and feeding experiments. Among the sampling stations examined, the spatial distribution of M. calcarea body size showed clear variations and was associated with phytoplankton size structure during the post-bloom period. In addition, our feeding experiment exposing M. calcarea to different feeding treatments suggest that the continuous settlement of fresh phytoplankton is more important for the bivalve's growth than the total amount of phytoplankton settlement. This could explain the significant linkage between M. calcarea body size and phytoplankton size structure during the post-bloom period, because the larger phytoplankton represent an influx of fresh phytoplankton to the sediment and hereby support better growth and/or longevity of bivalves. Our study provides novel insights into a variety of processes related to the growth of M. calcarea and its relationship with the phytoplankton community.

北极海冰的大量损失将在许多方面改变海洋生态系统。最近的研究报告说，太平洋北极底栖动物大型生物量的分布变化可能是由于底栖生物的食物供应量变化引起的。在这里，我们根据实地和卫星观测以及饲喂实验，评估了浮游植物向沉积物的开花后供应方面的差异对常见的太平洋北极双壳类（Macoma calcarea）生长的影响。在所检查的采样站中，钙华分枝杆菌体大小的空间分布显示出明显的变化，并且与开花后时期的浮游植物大小结构有关。此外，我们的喂养实验暴露了卡尔卡雷亚藻不同的饲养方法表明，新鲜浮游植物的持续沉降对双壳类动物的生长比浮游植物总沉降量更为重要。这可以解释在开花后时期，钙藻分枝杆菌的体型与浮游植物的大小结构之间的显着联系，因为较大的浮游植物代表新鲜的浮游植物涌入沉积物中，从而支持双壳类的更好的生长和/或长寿。我们的研究为与钙绿藻的生长及其与浮游植物群落的关系有关的各种过程提供了新颖的见解。