JGOFS (Arabian Sea): Effects of the Oxygen Minimum Zone on Mesozooplankton Distributions and Food Webs

9310590 Gowing这项研究是阿拉伯海全球海洋通量联合研究（JGOFS）的一部分，研究的问题是，阿拉伯海泛光带以下广泛存在的缺氧条件是否限制了后生动物的碳循环，主要局限于氧最低带以上和以下的区域，以及这是否会导致深海碳浓度（以浮游生物生物量的形式）升高。本项目有两个重点：(1)测量深海垂直地层中浮游动物的分布和大小分异生物量，特别关注氧气最小带及其上下界面；(2)研究氧气最小带对浮游动物营养关系的影响，包括潜在的浮游动物-细菌联系。在四个JGOFS集约站点，以及站点之间的横线间隔，将利用moness浮游生物网系统，在四个季节中日夜采集3500米以下的垂直分层浮游动物样本，以确定中浮游动物的分布和大小分异生物量。通过透射电子显微镜分析浮游动物的肠道内容物，以确定营养网。氧最低带的上下界面可能是浮游动物和颗粒丰度高、有机物加工强烈的地方，将成为研究分布和食物网的特别目标。中浮游动物在最低氧带内的丰度较低，可能有助于增加有机物质到海底的通量，因为这些营养动物对水中颗粒物质的利用将减少。中浮游动物的高丰度和在氧气最小区界面处的短食物链（细菌到浮游动物）表明，在狭窄的深度窗口内，有机物质被强烈处理，可能起到下沉颗粒的过滤器的作用。这项工作将有助于阐明有机物质在通过水柱到海底的过程中是如何改变的。它将有助于了解阿拉伯海的季节性季风周期和由此产生的生产力峰值如何与碳通量和沉积相关联，并可能为预测气候变化的影响提供类比。

9310590 Gowing This research, part of the Joint Gobal Ocean Flux Study (JGOFS) of the Arabian Sea, addresses the question of whether the widespread suboxic conditions below the euphotic zone in the Arabian Sea restrict carbon cycling by metazoans primarily to regions above and below the oxygen minimum zone and whether this results in elevated carbon concentrations (in the form of plankton biomass) at depth. This project has two foci: (1) the measurement of mesozooplankton distributions and size-fractionated biomass in vertical strata to the deep sea, with particular attention to the oxygen minimum zone and its upper and lower interfaces, and (2) examination of oxygen minimum zone effects on zooplankton trophic relationships, including the potential zooplankton-bacteria link. Vertically stratified zooplankton samples down to 3500 m will be taken during four seasons with a MOCNESS plankton net system day and night at the four intensive JGOFS stations and at intervals along transects between the stations for the determination of mesozooplankton distributions and size-fractionated biomass. Gut contents of zooplankton will be analyzed by transmission electron microscopy for determination of trophic webs. The upper and lower interfaces of the oxygen minimum zone, which may be locations of high zooplankton and particle abundances and intense processing of organic material, will be specially targetted for studies of distributions and food webs. Low mesozooplankton abundances within the oxygen minimum zone may contribute to enhanced fluxes of organic materials to the sea floor, because the utilizatimn of particulate material in midwater by these detritivores would be reduced. High mesozooplankton abundances and a short food chain (bacteria to zooplankton) at the oxygen minimum zone interfaces would suggest intense processing of organic material localized within a narrow depth window, possibly acting as a filter for sinking particles. This work will help elucidate how organic material may be altered during passage through the water column to the sea floor. It will contribute to understanding how the seasonal monsoon cycle of the Arabian Sea and resultant productivity peaks are coupled to carbon fluxes and deposition and may provide analogies for predicting effects of climate change.