Midwater anoxia disrupts the trophic structure of zooplankton and fish in an oxygen deficient zone

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Juan Gerardo Gutiérrez-Bravo, Mark A. Altabet, Laura Sánchez-Velasco, Sylvia Patricia Adelheid Jiménez-Rosenberg
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引用次数: 0

Abstract

Anoxic waters in the ocean's oxygen deficient zones (ODZs) limit the vertical migrations of zooplankton and mesopelagic fish impacting their ecology and influence on biogeochemical processes. Using an oxypleth-tracking, nighttime-only sampling protocol, this research reconstructed the trophic interactions of fish larvae and adults, and zooplankton, across the Eastern Tropical North Pacific ODZ. Bulk zooplankton δ15N increased latitudinally by ~ 3.3‰ from Costa Rica to Baja California due to anoxia-derived denitrification and consequent enrichment of nitrogen sources for producers. Zooplankton δ15N also increased with depth, with an abrupt 3.4‰ increase below the anoxic core (~ 900 m depth), indicating a distinct trophic structure in the resident zooplankton community. Above the anoxic core, δ15N was similar for fish larvae (10.1‰) and zooplankton (10.5‰), reflecting a shared food source. An exception was the hypoxia-tolerant myctophid Diogenichthys laternatus15N = 7.5‰) that possibly feeds on chemoautotrophy-derived material at the oxic-anoxic interface. The δ15N of fish adults residing below the anoxic core, like the meso-bathypelagic Notolychnus valdiviae (17.11‰) and Cyclothone spp. (15.89‰), was, on average, 4.8‰ higher than larval stages sampled at shallower depths, and 1.2‰ higher than zooplankton below the anoxic core. This stark increase in fish and zooplankton δ15N directly below the anoxic core suggests that anoxic waters act as a barrier for the downward trophic transfer by vertical migrants into the deep sea. Considering the current trends of ocean deoxygenation, this anoxia-derived disruption of the migrant pump could limit the carbon sequestration potential of ODZs.

水中缺氧破坏了缺氧区浮游动物和鱼类的营养结构
海洋缺氧带缺氧水域限制了浮游动物和中上层鱼类的垂直迁移,影响了它们的生态和生物地球化学过程。本研究采用夜间取样法,重建了北太平洋东部热带ODZ海域中鱼类幼虫、成虫和浮游动物之间的营养相互作用。从哥斯达黎加到下加利福尼亚,由于缺氧引起的反硝化作用和生产者氮源的富集,浮游动物体δ15N在纬度上增加了约3.3‰。浮游动物δ15N随深度增加,缺氧核心以下(~ 900 m深度)δ15N急剧增加3.4‰,表明浮游动物群落的营养结构明显。在缺氧核心上方,幼鱼(10.1‰)和浮游动物(10.5‰)的δ15N相似,反映了共同的食物来源。一个例外是耐缺氧的嗜氧菌Diogenichthys laternatus (δ15N = 7.5‰),它可能在缺氧-缺氧界面上以化学自养来源的物质为食。生活在缺氧岩心以下的成鱼的δ15N,如中深海Notolychnus valdiviae(17.11‰)和Cyclothone spp.(15.89‰),平均比在浅层取样的幼虫阶段高4.8‰,比缺氧岩心以下的浮游动物高1.2‰。缺氧核心下方的鱼类和浮游动物δ15N的明显增加表明,缺氧水域作为垂直迁移到深海的向下营养转移的屏障。考虑到目前海洋脱氧的趋势,这种缺氧引起的迁移泵的中断可能会限制odz的固碳潜力。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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