Physical Transport Mechanisms Driving Sub-Antarctic Island Marine Ecosystems
Physical Transport Mechanisms Driving Sub-Antarctic Island Marine Ecosystems
复制标题
驱动亚南极岛屿海洋生态系统的物理运输机制
作者：
A. Treasure;J. Ruzicka;E. Pakhomov;I. Ansorge
南大洋正在经历快速的环境变化，影响了其生态系统和食物网。生态系统模型需要纳入生物系统的各个层面并考虑物理环境。我们利用爱德华王子群岛 (PEI) 的端到端生态系统模型，研究了海洋养分、海洋浮游生物和陆地铵径流输入对近岸生产的重要性。我们将生态系统状态作为群体生产率以及交替洋流状况下中上层与底层食物网路径的相对规模、大型浮游动物平流进入陆架水域的假设以及浮游生物保留在近岸区域的假设进行了比较。主要成果是：（1）海洋浮游生物比海洋营养物或陆地营养物更成为近岸生态系统内所有群体生产的主要驱动力。岛屿上的铵径流是生产的一个次要驱动因素，但对于高度依赖碎屑食物链的群体（底栖无脊椎动物、底层鱼类、巴布亚企鹅）来说最为重要； (2) 对洋流状况的变化和大型浮游动物平流进入陆架水域的假设最敏感的群体是浮游动物（南跳岩企鹅、马卡罗尼企鹅）和食鱼动物，其饮食严重依赖浮游食鱼； (3) 如果浮游动物种群表现为纯粹的被动漂流者，则它们无法支持近岸生态系统内估计的捕食压力水平。我们的研究结果表明，物理过程的变化，例如假设的亚南极锋位置向南移动，导致接近岛屿的洋流加剧，已经并将继续对爱德华王子岛生态系统产生重大影响。
The Southern Ocean is undergoing rapid environmental change, which has impacted its ecosystems and food webs. There is need for ecosystem models that incorporate all levels of the biotic system and consider physical context. Using an end-to-end ecosystem model of the Prince Edward Islands (PEIs), we investigated the importance of the input of oceanic nutrients, oceanic plankton, and run-off of terrestrial ammonium to nearshore production. We compared ecosystem state as group production rates and as the relative scale of pelagic versus demersal food web pathways under alternate ocean current regimes, assumptions of macrozooplankton advection into shelf waters, and assumptions of plankton retention within the nearshore region. The major outcomes are: (1) oceanic plankton, more than oceanic nutrients or terrestrial nutrients, is the major driver of production for all groups within the nearshore ecosystem. Island run-off of ammonium is a minor driver of production but is most important among groups with higher reliance upon detrital food chains (benthic invertebrates, demersal fishes, Gentoo penguins); (2) groups most sensitive to changes in ocean current regime and assumptions of macrozooplankton advection into shelf waters are planktivores (southern rockhopper penguins, Macaroni penguins) and piscivores whose diets rely heavily upon planktivorous fishes; (3) zooplankton populations cannot support estimated levels of predation pressure within the nearshore ecosystem if they behave as purely passive drifters. Our findings suggest changes to physical processes, such as a postulated southward shift in the position of the sub-Antarctic front leading to intensification of currents approaching the islands, has already had and will continue to have significant impacts on the PEIs ecosystem.