Feeding Ecology of Three Euphausiid Species in the North Pacific Ocean Inferred From 18S V9 Metabarcoding and Stable Isotope Analysis
Feeding Ecology of Three Euphausiid Species in the North Pacific Ocean Inferred From 18S V9 Metabarcoding and Stable Isotope Analysis
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DOI：
10.3389/fmars.2021.756067
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
Fanyu Zhou;Junya Hirai;K. Hamasaki;S. Horii;A. Tsuda
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作者：
Fanyu Zhou;Junya Hirai;K. Hamasaki;S. Horii;A. Tsuda
磷虾科是丰富的微游生物，是海洋生态系统中高营养级和低营养级之间的重要联系；然而，传统显微镜无法完全了解它们的详细饮食，尤其是在亚热带地区。在这里，我们报告了加州洋流 (CC) 地区和北太平洋东/西副热带环流 (ESG 和 WSG) 的磷虾群落结构，并使用 18S V9 元条形码和稳定碳氮同位素分析的肠道内容物分析相结合的方法，详细介绍了每个区域的优势物种（磷虾、短磷虾和 E. hemigibba）的摄食生态。两种方法都支持所有研究的磷虾科物种明显的杂食性：在肠道内容物中检测到浮游植物分类群（甲藻门、原生藻纲和古质体纲）、桡足纲和水螅纲；所有三种磷虾科物种都表现出介于净浮游生物（0.2-1.0毫米）和蕈鱼（15.2-85.5毫米）之间的中间营养位置。然而，根据同位素分析，水螅发现磷虾的肠道内容物可能来自潜在的鳕鱼末端喂养。由于CC省浅水层的原生藻菌和古质体数量较多，CC省的太平洋真鲨摄入了更多的自养猎物，包括水生植物和绿藻。另一方面，非自养猎物，如混合营养型卡氏甲藻、Pontellidae 和 Clausocalanidae 桡足类，以及 Sphaerozoidae rhizarian 对 E. brevis 和 E. hemigibba 的饮食贡献更大，因为 ESG 和 WSG 中叶绿素浓度较低，或者可能缺乏自养猎物。因此，进行滤食的优势磷虾物种的摄食模式很大程度上取决于环境中浮游植物猎物的可用性。稳定同位素分析也表明了三个物种之间的饮食差异，太平洋桉树 (2.32) 的平均营养水平低于短桉树 (2.48) 和半吉巴桉树 (2.57)。这些结果验证了磷虾和初级生产之间的直接营养相互作用，并表明杂食性食性是优势磷虾物种的有利特征。
Euphausiids are abundant micronekton and important links between higher and lower trophic levels in marine ecosystems; however, their detailed diets cannot be fully understood by conventional microscopy, especially in subtropical areas. Here, we report the euphausiid community structure in the California Current (CC) area and the eastern/western North Pacific subtropical gyre (ESG and WSG) and detail the feeding ecology of the dominant species (Euphausia pacifica, E. brevis, and E. hemigibba) in each region using a combined approach of gut content analysis via 18S V9 metabarcoding and stable carbon and nitrogen isotope analysis. A pronounced omnivorous feeding of all studied euphausiid species was supported by both methods: phytoplanktonic taxonomic groups (Dinophyta, Stramenopiles, and Archaeplastida), Copepoda, and Hydrozoa were detected in the gut contents; all the three euphausiid species displayed an intermediate trophic position between the net plankton (0.2–1.0 mm) and the myctophid fish (15.2–85.5 mm). However, Hydrozoa found in euphausiid gut contents likely derived from a potential cod-end feeding, based on isotope analysis. E. pacifica in the CC province ingested more autotrophic prey, including pelagophyte and green algae, due to a greater abundance of Stramenopiles and Archaeplastida in shallow layers of CC water. On the other hand, non-autotrophic prey such as mixotrophic Kareniaceae dinoflagellates, Pontellidae and Clausocalanidae copepods, and Sphaerozoidae rhizarian contributed more to the diets of E. brevis and E. hemigibba because of a lower chlorophyll a concentration or potentially a scarcity of autotrophic prey availability in ESG and WSG. The feeding patterns of dominant euphausiid species conducting filter feeding were thus largely determined by phytoplankton prey availability in the environments. Dietary difference across three species was also indicated by stable isotope analysis, with a lower mean trophic level of E. pacifica (2.32) than E. brevis (2.48) and E. hemigibba (2.57). These results verify direct trophic interactions between euphausiids and primary production and suggest that the omnivorous feeding habit is a favorable character for dominant Euphausia species.