Knowledge on the distribution of zooplankton in the many unique habitats of the Southern Ocean is essential for understanding food web dynamics, assessing the impacts of environmental change and for managing the exploitation of marine living resources. Variation in the distribution of zooplankton may occur in the horizontal as well as the vertical plane, and the latter may show a diel cycle (diel vertical migration or DVM). Conventional sampling methods, including several types of nets and acoustics, often undersample or ignore the top 10 m of the water column. The surface waters may, however, host a specific zooplankton community and therefore be an important foraging ground for higher trophic level predators. In order to investigate the importance of the surface waters for understanding the distribution of species and potentially improving abundance estimates, the upper two meters of the water column were sampled in the eastern Indian sector of the Southern Ocean using a Surface and Under Ice Trawl (SUIT). Findings were compared to the zooplankton community structure in the epipelagic (15–200 m). Results showed that the surface zooplankton community could largely be divided into two regions. The surface community of the western side of the sampling area hosted large numbers of Antarctic krill, , which were only present in low densities in the epipelagic depth layer. Densities of were also relatively high in the west. The copepod and the amphipod were present in relatively large numbers throughout the sampling area. was the dominant species of the surface in the eastern side of the sampling area in the absence of Antarctic krill. Apart from cirripedia nauplii, no species were uniquely found in the surface water compared to the 15–200 m depth layer. Surface water sampling revealed patterns in vertical distribution and DVM, and showed that these patterns changed between the first and second half of the expedition. This could partially be explained by environmental variables but was likely also a result of sampling time and location, and associated variation in the size and ontogeny of species. Results revealed the impact of undersampling the surface layer regarding knowledge on distribution and vertical migration patterns of zooplankton species.

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2018/2019年南半球夏季南大洋东印度区海面浮游动物群落


有关南大洋许多独特栖息地中浮游动物分布的知识对于了解食物网动态、评估环境变化的影响以及管理海洋生物资源的开发至关重要。浮游动物的分布变化可能发生在水平面和垂直面，垂直面可能表现出昼夜循环（昼夜垂直迁移或DVM）。传统的采样方法，包括多种类型的网络和声学采样方法，通常采样不足或忽略水柱顶部 10 m 的部分。然而，地表水域可能存在特定的浮游动物群落，因此是高级营养级捕食者的重要觅食地。为了调查地表水对于了解物种分布和可能改善丰度估计的重要性，使用表层和冰下拖网（SUIT）在南大洋东印度部分对水柱上部两米进行了采样。 ）。研究结果与表层（15-200 m）的浮游动物群落结构进行了比较。结果表明，表层浮游动物群落大致可分为两个区域。采样区西侧的表层群落栖息着大量的南极磷虾，它们仅以低密度存在于表层深层。西部地区的密度也相对较高。整个采样区域中桡足类和片足类动物的数量相对较多。在没有南极磷虾的情况下，是采样区东侧地表的优势物种。除无节幼体无节幼体外，与 15-200 m 深度相比，地表水中没有发现独特的物种。 地表水采样揭示了垂直分布和 DVM 的模式，并表明这些模式在探险的前半段和后半段之间发生了变化。这可以部分地用环境变量来解释，但也可能是采样时间和地点以及物种大小和个体发育的相关变化的结果。结果揭示了表层欠采样对浮游动物物种分布和垂直迁移模式知识的影响。