Copepod community structure in the transition region of the North Pacific Ocean: Water mixing as a key driver of secondary production enhancement in subarctic and subtropical waters
Copepod community structure in the transition region of the North Pacific Ocean: Water mixing as a key driver of secondary production enhancement in subarctic and subtropical waters
复制标题
北太平洋过渡区桡足类群落结构：水混合是亚北极和亚热带水域二次生产增强的关键驱动力
DOI：
10.1016/j.pocean.2022.102865
复制
发表时间：
2022
影响因子：
4.1
通讯作者：
Tadokoro Kazuaki
中科院分区：
文献类型：
--
作者：
Miyamoto Hiroomi;Takahashi Kazutaka;Kuroda Hiroshi;Watanabe Tsuyoshi;Taniuchi Yukiko;Kuwata Akira;Kasai Hiromi;Kakehi Shigeho;Fuji Taiki;Suyama Satoshi;Tadokoro Kazuaki
北太平洋副热带-亚北极环流过渡区被认为是重要的小型中上层鱼类养殖场和摄食场。为了阐明过渡区域远洋生态系统的低营养级变化，我们调查了桡足类群落的大尺度变化与海洋环境的关系。2017年和2018年初夏，我们在距离海岸150米以上至以东约4,500公里(东经140°，−，西经165°)的海域对浮游动物进行了净采样。根据233个采样站的丰度和物种组成进行的聚类分析表明，亚北极界线--以150米深处盐度34.0为界--将亚北极和亚热带桡足类群落分开，作为一条明确的生物地理边界。这两个社区分别被进一步划分为四个亚组。在亚群中，一个典型的亚北极亚群由Neocalanusspp.在亚北极HNLC(高营养低叶绿素浓度)区广泛分布，而在温暖的贫营养水中出现了一个典型的亚热带亚群，以物种多样性较高为特征。此外，在这两个亚组中，叶绿素大小部分的组成表明，食物网主要以小型浮游植物为基础。对其他亚类的进一步分析表明，亚热带和亚北极群落都表现出不同的演替模式，这取决于水的混合程度。在演替过程中，在两个主要群落中都观察到了与大型硅藻高生产力相关的桡足类丰度的持续增加，特别是大型悬浮摄食者(如真水蚤和水蚤)。本研究表明，过渡区域的水混合持续加强了亚热带和亚北极社区的放牧食物链，显示了控制小型中上层鱼类猎物可获得性的潜在潜在机制，这些机制将该区域作为关键的育苗和觅食场所。
The North Pacific Ocean subtropical–subarctic gyre transition region is recognized as an important small pelagic fish nursery and feeding ground. To clarify the lower trophic level variability of the transition region pelagic ecosystem, we investigated the large-scale variation in copepod communities in relation to the oceanographic environment. We net sampled zooplankton in the upper 150 m from the coast to approximately 4,500 km offshore to the east (140° E − 165° W) during early summer in 2017 and 2018. Cluster analysis based on abundance and species composition at 233 sampling stations showed that the subarctic boundary, defined by a salinity of 34.0 at 150 m depth, separated subarctic and subtropical copepod communities, as a clear biogeographical border. The two communities were each further classified into four subgroups. Among the subgroups, a typical subarctic subgroup dominated byNeocalanusspp. was broadly distributed in the subarctic HNLC (high-nutrient and low-chlorophyllaconcentrations) region, whereas a typical subtropical subgroup characterized by a higher overall species diversity occurred in the warm oligotrophic water. In addition, in both these subgroups, the composition of the chlorophyllasize fraction suggested that the food web was mainly based on small-sized phytoplankton. Further analysis of the other subgroups indicated that both the subtropical and subarctic communities showed distinctive succession patterns depending on the degree of water mixing. During succession, a consistent increase in copepod abundance, especially large-sized suspension feeders (e.g.,EucalanusandCalanus) associated with the high productivity of large diatoms was observed in both main communities. The present study revealed that water mixing in the transition region consistently enhances the grazing food chain in both subtropical and subarctic communities, showing the potential underlying mechanisms of control of prey availability for small pelagic fish that exploit the region as a key nursery and feeding ground.