Grazing and Carbon Cycling by the Epipelagic Crustacean Zooplankton of the Arabian Sea

在我们星球上任何地方观测到的一些最强的大气对海洋特性的强迫是在阿拉伯海，那里季节性的季风逆转驱动着快速流动的、垂直扩展的洋流、复杂的涡流场、大规模的、开放的海洋上升流、沿海上升流和明显的混合层加深。这个地区的生产周期是季节性的波动。在西南季风季节（包括6 - 9月），初级生产力是最大的，因为强风不仅使富含养分的深水抬升，而且将风沙带到热带海洋的表层。在东北季风（包括10 - 11月）和季风间期，初级生产力显著降低。在西南季风季节，浮游动物生物量和次生生产力也有所增加。根据索马里海域的早期研究，假设阿曼海域的上层浮游动物在一个季风季节到另一个季风季节之间的物种组成发生了重大变化，西南季风期间的生物量主要是快速增长的中型和大型浮游动物食草动物，如Calanoides和Eucalanus。在其他季节，这些食草动物在地下深处的数量有所减少。相对大型、快速生长的食草动物的季节性出现，在很大程度上决定了浮游动物群落在西南季风（上升流）期间对阿拉伯海浮游植物组合的放牧影响。放牧影响反过来调节了碳向深度的通量，是影响该地区碳沉积时空格局的重要因素。在阿曼附近的阿拉伯海，可以结合对阿拉伯海中部常年少营养区放牧对碳通量贡献的调查，研究上升流区放牧群落的大规模季节性变化所驱动的碳通量。在大约一百五十米的地方，氧浓度有一个陡峭的梯度，把大多数上层海洋的食草动物限制在这个深度以上的表层。将使用多重开/闭网（moness）来确定分布和丰度，特别关注氧-缺氧界面和孵化实验来确定摄食、粪便颗粒产生和生长速度，研究上层浮游中、大型浮游动物食草动物的作用

Smith 9310599 Some of the strongest atomspheric forcing of oceanic properties anywhere on our planet is observed in the Arabian Sea where seasonally reversing monsoon winds drive fast- flowing, vertically extensive currents, complex eddy fields, broad-scale, open ocean upwelling, coastal upwelling and pronounced mixed-layer deepening. Cycles of production in this region are seasonal oscillations. During the southwest monsoon season (June-September inclusive), primary productivity is maximal owing to strong winds which not only cause the uplift of deep water rich in nutrient, but also deliver aeolian dust to the surface layer of this tropical ocean. During the northeast monsoon (October-November inclusive) and intermonsoon periods, primary productivity is markedly reduced. Biomass of zooplankton and secondary productivity are also elevated during the southwest monsoon season. Based upon earlier studies off Somalia, the epipelagic zooplankton off Oman is hypothesized to undergo significant changes in species composition from one monsoon season to another, with biomass during the southwest monsoon dominated by rapidly growing meso- and macrozooplanktonic grazers such as Calanoides and Eucalanus. These grazers exist in reduced abundance at subsurface depths during other seasons. The seasonal appearance of relatively large, fast growing grazers determines, to a large extent, the grazing impact of the zooplanktonic community on the phytoplankton assemblage that develops in the Arabian Sea during the southwest monsoon (upwelling). The grazing impact in turn modulates the flux of carbon to depth and is an important factor in the spatial and temporal patterns in carbon deposition in this region. In the Arabian Sea off Oman, carbon fluxes driven by large, seasonal changes in the grazing community of the upwelling area can be studied in combination with investigation of the grazing contribution to carbon fluxes associated with the perennially oligotrophi c region of the central Arabian Sea. A steep gradient in oxygen concentration located at approximately 150 meters acts to restrict most epipelagic grazers to a surface layer above this depth. The role of the epipelagic meso- and macrozooplanktonic grazers will be studied using: multiple opening/closing nets (MOCNESS) to determine distribution and abundance with particular attention to the oxic-suboxic interface and incubation experiments to determine ingestion, fecal pellet production, and growth rates