Seasonal patterns in mesozooplankton composition, vertical distribution, and timing of reproduction are challenging to study in the open sea due to ocean currents and mix of populations of different origins. Sill fjords, on the other hand, with restricted water exchange, are ideal locations for studying taxa- and community-specific adaptations to the prevailing environment. Here, we present re-occurring patterns in the mesozooplankton community structure in Billefjorden, Svalbard, a high Arctic sill fjord with extensive seasonal ice cover, based on monthly sampling from 2011 to 2013. The zooplankton community composition confirmed the Arctic character of this fjord. Predominantly herbivorous taxa, such as Calanus glacialis and Pseudocalanus spp., showed strong seasonal variation in abundance and depth distribution, with population minima in spring being compensated by a rapid population recovery during summer. Omnivorous taxa, such as Microcalanus spp. and copepods of the family Aetideidae, largely remained at depth throughout the year and had an extended or year-round reproductive period. Deep-dwelling omnivorous/carnivorous species peaked in abundance in winter–spring when herbivorous populations were severely depleted. Taxa with seasonally limited occurrences, i.e., meroplankton, peaked in spring and summer at the surface, but were largely absent for the rest of the year. The different life histories, with contrasting feeding modes, depth preferences, and timing of reproduction lead to reduced interspecies competition and allow for a rather high and stable abundance of mesozooplankton year-round despite the short primary production window at high latitudes.

由于洋流和不同来源种群的混合，在公海中研究中型浮游生物组成、垂直分布和繁殖时间的季节性模式具有挑战性。另一方面，水交换受限的 Sill 峡湾是研究类群和群落对当前环境的适应的理想地点。在这里，我们根据 2011 年至 2013 年的月度采样，展示了斯瓦尔巴群岛 Billefjorden 的中型浮游动物群落结构中反复出现的模式，这是一个具有广泛季节性冰盖的北极高峡湾。浮游动物群落组成证实了该峡湾的北极特征。主要是草食性分类群，例如Calanus glacialis 和 Pseudocalanusspp.，在丰度和深度分布方面表现出强烈的季节性变化，春季的种群最小值被夏季的快速种群恢复所补偿。杂食性分类群，例如微孔spp. 和家庭的桡足类鸟科，全年基本保持在深度，并有一个延长或全年的繁殖期。当草食性种群严重枯竭时，深栖杂食性/肉食性物种的数量在冬春季达到顶峰。季节性有限的类群，即浮游生物，在春季和夏季在地表达到顶峰，但在今年余下时间基本不存在。不同的生活史、不同的摄食模式、深度偏好和繁殖时间导致物种间竞争减少，尽管高纬度地区初级生产窗口较短，但全年中浮游动物的丰度相当高且稳定。