Table_1_Differential Impact of the Khatanga and Lena (Laptev Sea) Runoff on the Distribution and Grazing of Zooplankton.docx

The ecosystems of the Arctic Ocean and their expected changes in a context of Global climate processes are crucially dependent on the freshwater input. The freshwater signal is assumed to be the main structuring factor for the marine fauna on the shallow shelf of the Siberian Arctic seas. The Laptev Sea, as a part of the world’s widest continental shelves surrounding the Arctic Ocean, is a key area for understanding the land–ocean interaction in high latitude regions. The largest freshwater input is provided by the deltaic Lena river followed by the estuarine Khatanga river. The plumes of these rivers differ considerably in their hydrophysical characteristics, suggesting differential impacts on ecosystems of the adjacent shelf. The key component of pelagic ecosystems is zooplankton, which transfers energy from primary producers to higher trophic levels and modifies sedimentations processes. This study is focused on the influence of river discharge on zooplankton in the Laptev Sea at the end of productive season. We studied zooplankton biomass, species composition, distribution patterns of the dominant species and assessed herbivorous feeding rates and grazing pressure of these species along a transect from the inner Khatanga Gulf northward to the continental slope, and a transect in the Lena plume influenced area in August-September 2017. Despite large spatial extension of the Khatanga plume, the impact of river discharge on zooplankton species composition was restricted mainly to the inner Gulf where the brackish species shaped the community. Contrary to the Khatanga input, the Lena freshwater inflow was highly variable and under certain conditions (discharge rate, wind forcing) governed the structure of zooplankton community over a vast shelf area. Distribution patterns of zooplankton biomass, ingestion rates and grazing impact of the dominant species on phytoplankton over the shelf influenced by the Khatanga and Lena plumes were similar. Analysis of our results on demographic structure of Calanus glacialis suggests that seasonal development of the population was largely controlled by the time of ice retreat. Observed climatic changes in the Arctic were not reflected in the total zooplankton biomass and composition of the dominant species.

北极海洋的生态系统及其在全球气候过程背景下的预期变化，对淡水输入的依赖至关重要。淡水信号被认为是西伯利亚北极海域浅水架上海洋生物群落的主要结构因素。作为环绕北极海洋最广阔的大陆架的一部分，拉普捷夫海是理解高纬度地区陆地-海洋相互作用的关键区域。最大的淡水输入由列纳三角洲河流提供，其次是哈坦加河口河流。这些河流的羽状流在水文物理特性上存在显著差异，表明它们对邻近架上海洋生态系统的影响存在差异。浮游生态系统的重要组成部分是浮游动物，它将初级生产者转移的能量传递到较高营养级，并改变沉积过程。本研究专注于研究河流排放对拉普捷夫海浮游动物在生产力季节末的影响。我们研究了浮游动物生物量、物种组成、优势物种的分布模式，并评估了这些物种的食草摄食率和放牧压力，这些研究是在2017年8月至9月期间，从哈坦加海湾内部向北至大陆坡的横断面，以及受列纳羽状流影响的区域进行的。尽管哈坦加羽状流的横向扩展范围很大，但河流排放对浮游动物物种组成的影响主要限于海湾内部，那里咸水物种塑造了群落。与哈坦加输入相反，列纳淡水流入量高度多变，在特定条件下（排放速率、风力驱动）决定了广大架上海洋浮游动物群落的结构。受哈坦加和列纳羽状流影响的架上海域上浮游动物生物量、摄食率和优势物种对浮游植物的放牧影响分布模式相似。我们对北极环状海冰的种群结构分析表明，该种群的季节性发展主要受冰撤退时间控制。观察到的北极气候变化并未在总浮游动物生物量和优势物种组成中反映出来。