SGER: Food Web Structure Across a Large-scale Ocean Productivity Gradient: Top Predator Assemblages in the Southern Indian Ocean

生物海洋学的一个普遍目标是了解构成远洋群落的过程。过去的研究表明，海洋物种分布在不同的时空尺度上受到物理和生物变异性的影响。这项研究的目的是检验这一假设，即顶级捕食者的分散度和群落与海洋生态系统中物理结构和海洋生产力的大范围变异性相一致。为了验证这一假设，将对南印度洋不同海洋领域的海洋鸟类和哺乳动物的使用情况进行跨学科调查。这笔用于探索研究的小额赠款将提供机会，将两名美国科学家送上留尼汪岛附近的一艘法国考察船。法国科学家将对物理环境进行采样，并估计海洋生产力，而美国科学家将调查从亚热带到亚南极水域35度纬度梯度上的顶级捕食者分布情况。要解决的主要假设是，顶级捕食者的组合是由水文特性和海洋生产力模式的空间梯度构成的，这些已知影响其浮游动物、鱼类和鱿鱼猎物的分布和斑块。假设特定海洋领域内海洋顶端捕食者的总体丰度在很大程度上由海洋生产力决定。此外，还假设觅食的能量成本决定了哪些类型的海洋顶级捕食者生活在特定的海洋领域。觅食成本高的物种被限制在高生产力地区开发密集的猎物聚集地。相反，觅食成本低的分类群能够栖息在低生产力地区，在那里它们利用更分散的猎物资源。为了检验这些假设，我们将量化顶级捕食者群落与特定水团的空间联系，以及顶级捕食者水深和水深区域的聚集反应。由于顶级捕食者在多个时间和空间尺度上对海洋变异性做出反应，我们将在两个特定的空间尺度上评估它们对栖息地变异性的反应。将使用各种分析方法，包括粗尺度生境偏好的成分分析、广义相加模型、轮回群体分析、水文数据和顶级捕食者组合的排序以及顶级捕食者聚集度的测量。这项研究将在亚热带和亚南极印度洋的大尺度(1000千米)和粗尺度(10S千米)水文和海洋生产力模式的背景下，研究远洋食物网的空间变异性。这种跨学科的观点将加强我们对南印度洋中上层海洋群落结构的物理和生物过程的了解，并将提供一个对整个海洋具有更广泛影响的模式。

A pervasive goal of biological oceanography has been to understand the processes that structure pelagic communities. Past research suggests that oceanic species distributions are influence by physical and biological variability at a variety of spatial-temporal scales. The objective of this research is to test the hypothesis that the dispersion and community of top predators vary in concordance with large-scale variability in physical structure and ocean productivity in pelagic ecosystems. To test this hypothesis, an inter-disciplinary survey of marine bird and mammal use of distinct oceanographic domains in the Southern Indian Ocean will be conducted. This Small Grant for Exploratory Research will provide the opportunity to place two U.S. scientists on board a French research vessel near Reunion Island. The French scientists will sample the physical environment and estimate oceanic productivity while the U.S. scientists will survey top predator distributions across a 35 degree latitudinal gradient in physical and biological properties from subtropical to sub Antarctic waters. The primary hypothesis to be addressed is that top predator assemblages are structured by spatial gradients in hydrographic properties and ocean productivity patterns known to influence the distribution and patchiness of their zooplankton, fish and squid prey. It is hypothesized that the overall abundance of marine top predators within a specific oceanic domain is largely determined by ocean productivity. Also, it is hypothesized that the energetic costs of foraging determine which types of marine top predators inhabit specific oceanic domains. Species with high foraging costs are constrained to exploit dense prey aggregations within highly productive areas. Conversely, taxa with low foraging costs are able to inhabit low productivity areas, where they exploit more dispersed prey resources.To test these hypotheses, we will quantify the spatial association of top predatorassemblages with specific water masses and the aggregative response of top predators athydrographic and bathymetric domains. Because top predators respond to oceanographicvariability at multiple scales of time and space, we will assess their responses tohabitat variability at two specific spatial scales. A variety analytical methods will be used, including compositional analysis of coarse-scale habitat preferences, generalized additive models, recurrent group analysis, ordination of hydrographic data and top predator assemblages and the measurement of top predator aggregation. The research will address spatial variability in pelagic food webs within the context of large (1000s km) and coarse (10s km) scale hydrographic and ocean productivity patterns in the subtropical and sub Antarctic Indian Ocean. This inter-disciplinary perspective will enhance our understanding of the way physical and biological processes structure pelagic communities in the southern Indian Ocean and will provide a model that has broader implications for the oceans as a whole.