IntroductionIn the Southern Ocean, the large-scale distribution of zooplankton, including their abundance and community composition from the epipelagic to the upper bathypelagic layers, remains poorly understood. This gap in knowledge limits our comprehension of their ecological and biogeochemical roles.MethodsTo better understand their community structure, depth-stratified zooplankton samples were collected from 0 to 1500 m during four summers in the East-Pacific and Indian sectors of the Southern Ocean. In addition, analysis of environmental drivers including temperature, salinity, dissolved oxygen, and chlorophyll a concentration, as well as water masses was conducted.ResultsOur study indicates that zooplankton diversity may be similar between the two sectors, while zooplankton abundance was higher in the East-Pacific sector during different sampling months and years. Moreover, zooplankton abundance decreased with depth in both sectors. Based on cluster analysis, zooplankton communities were generally divided by either the epipelagic or the deeper layers’ communities. In both sectors, the epipelagic layer was dominated by cyclopoid copepods, such as Oithona similis and Oncaea curvata, as well as calanoid copepods including Calanoides acutus, Rhincalanus gigas, and Ctenocalanus citer, while copepods and other taxa including Chaetognatha, Amphipoda, and Ostracoda, were important contributors to the deep layer communities.DiscussionOur analysis revealed that water masses, combined with their physical characteristics such as specific temperature and salinity ranges and depth, along with biological factors such as chlorophyll a concentration, might be the most important drivers for structuring zooplankton communities from epipelagic to upper bathypelagic layer.

中文翻译：

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南大洋东太平洋和印度区浮游动物垂直分层


简介在南大洋，浮游动物的大规模分布，包括从表层到深海层的丰度和群落组成，人们仍然知之甚少。这种知识上的差距限制了我们对其生态和生物地球化学作用的理解。方法为了更好地了解它们的群落结构，在四个夏季期间，在东太平洋和南大洋印度洋区采集了 0 至 1500 m 深度的浮游动物样本。此外，还对温度、盐度、溶解氧、叶绿素 a 浓度以及水团等环境驱动因素进行了分析。结果我们的研究表明，两个部门之间的浮游动物多样性可能相似，而东部地区的浮游动物丰度较高-不同采样月份和年份的太平洋部门。此外，这两个区域的浮游动物丰度随着深度的增加而减少。基于聚类分析，浮游动物群落一般按上层或深层群落划分。在这两个区域，表层桡足类以圆足类桡足类为主，例如Oithona similis和Oncaea curvata，以及桡足类桡足类包括Calanoides acutus、Rhincalanus gigas和Ctenocalanus citer，而桡足类和其他类群包括毛颌动物、片足动物和介形动物，是深层群落的重要贡献者。讨论我们的分析表明，水团结合其物理特征（例如特定的温度和盐度范围和深度）以及生物因素（例如叶绿素 a 浓度）可能是浮游动物结构的最重要驱动因素从表层到上深海层的群落。