Plankton abundance and feeding characteristics of Thysanoessa raschii from Godthabsfjord, Greenland

Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the Godthabsfjord (64°N, 51°W) SW Greenland, through a combination of fieldwork and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily ration of 1% body C/d. Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 µm, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory behaviour of krill will concentrate and elevate the grazing in specific areas of the euphotic zone.尽管磷虾是关键的浮游动物类群，但目前学界对北极海域磷虾生物学的认知仍存在不足。本研究结合野外调查与室内实验，对格陵兰西南部戈特霍布峡湾（Godthabsfjord，64°N，51°W）内磷虾的功能生物学展开探究，并评估其营养生态作用。磷虾生物量在峡湾中部与内层峡湾达到峰值，外海未检出磷虾。优势种拉氏磷虾（Thysanoessa raschii）在取食硅藻威氏海链藻（Thalassiosira weissflogii）时，表现出III型功能响应。在食物饱和状态下，拉氏磷虾的日摄食量为体重碳的1%/天。此外，拉氏磷虾可利用5~400μm粒径的浮游细胞，覆盖浮游食物网的多个营养层级。经计算，拉氏磷虾对峡湾浮游群落的整体牧食压力可忽略不计，但磷虾的集群与迁移行为会在真光层的特定区域形成种群聚集，并提升局部牧食强度。