Dominant pelagic amphipods collected as swimmers from a mooring time-series at AWI HAUSGARTEN

Time series length-frequency data are presented for Themisto amphipods collected as swimmers by moored sediment traps since 2000 at the AWI deep-sea observatory HAUSGARTEN (79°N/4°E) in the eastern Fram Strait. Amphipod occurrences increased significantly from 2000 to 2009 at 200-300 m depth, and the North Atlantic species Themisto compressa was continuously present in the samples starting in 2004. We present year-round records of large adult Themisto amphipods, including the appearance of Themisto libellula with a total body length of up to 56.7 mm and juveniles starting from 4.0 mm. The length of Themisto abyssorum ranged from 4.2 to 25.6 mm, whereas it varied for Themisto compressa from 8.8 to 24.4 mm. Length-frequency analysis indicated a life span of 2 years for T. abyssorum and at least 3 years for T. libellula. The absence of juveniles for T. compressa suggested its reproduction in southern subarctic areas and its occasional northward migration with warmer Atlantic water into the eastern Fram Strait. The seasonal and long-term size structures of the three pelagic species were consistent over the course of the study, indicating no changes occurred in cohort development due to increasing abundances or warming water temperatures.

本数据集收录了2000年以来，在弗拉姆海峡东部阿尔弗雷德·魏格纳极地与海洋研究所（AWI）HAUSGARTEN深海观测站（北纬79°/东经4°），通过锚定沉积物捕集器采集的美肢水蚤属（Themisto）端足类（Amphipoda）游动个体的体长频率时间序列数据。2000年至2009年间，200~300米水深的端足类捕获量显著上升；北大西洋物种扁平美肢水蚤（Themisto compressa）自2004年起持续出现在采样样本中。本数据集包含全年观测的大型成体美肢水蚤属端足类记录，其中包括最大体长可达56.7毫米的精致美肢水蚤（Themisto libellula）以及体长4.0毫米起的幼体。深渊美肢水蚤（Themisto abyssorum）的体长范围为4.2~25.6毫米，而扁平美肢水蚤的体长则介于8.8~24.4毫米之间。体长频率分析结果显示，深渊美肢水蚤的寿命为2年，精致美肢水蚤的寿命至少为3年。扁平美肢水蚤未检出幼体样本，这表明其繁殖地位于南部亚北极区域，并随大西洋暖水偶尔向北迁徙进入弗拉姆海峡东部海域。本研究周期内，三种浮游性物种的季节与长期体长结构均保持稳定，表明其种群世代发育未因种群丰度上升或海水温度升高而发生改变。