Department of Coastal Sciences, University of Southern Mississippi, Gulf Coast Research Laboratory, 703 East Beach Drive, Ocean Springs, Mississippi 39564, USA.
Ecol Appl. 2010 Jun;20(4):915-34. doi: 10.1890/08-1796.1.
Many of the world's coastal ecosystems are impacted by multiple stressors each of which may be subject to different management strategies that may have overlapping or even conflicting objectives. Consequently, management results may be indirect and difficult to predict or observe. We developed a network simulation model intended specifically to examine ecosystem-level responses to management and applied this model to a comparison of nutrient load reduction and restoration of highly reduced stocks of bivalve suspension feeders (eastern oyster, Crassostrea virginica) in an estuarine ecosystem (Chesapeake Bay, USA). Model results suggest that a 50% reduction in nutrient inputs from the watershed will result in lower phytoplankton production in the spring and reduced delivery of organic material to the benthos that will limit spring and summer pelagic secondary production. The model predicts that low levels of oyster restoration will have no effect in the spring but does result in a reduction in phytoplankton standing stocks in the summer. Both actions have a negative effect on pelagic secondary production, but the predicted effect of oyster restoration is larger. The lower effect of oysters on phytoplankton is due to size-based differences in filtration efficiency and seasonality that result in maximum top-down grazer control of oysters at a time when the phytoplankton is already subject to heavy grazing. These results suggest that oyster restoration must be achieved at levels as much as 25-fold present biomass to have a meaningful effect on phytoplankton biomass and as much as 50-fold to achieve effects similar to a 50% nutrient load reduction. The unintended effect of oyster restoration at these levels on other consumers represents a trade-off to the desired effect of reversing eutrophication.
世界上许多沿海生态系统都受到多种胁迫因素的影响，其中每一种因素都可能受到不同的管理策略的影响，这些策略可能有重叠甚至冲突的目标。因此，管理结果可能是间接的，难以预测或观察。我们开发了一种网络模拟模型，旨在专门研究管理对生态系统水平的响应，并将该模型应用于比较营养负荷减少和恢复高度还原的双壳类滤食性动物（东方牡蛎，Crassostrea virginica）在一个河口生态系统（美国切萨皮克湾）中的作用。模型结果表明，流域养分输入减少 50%将导致春季浮游植物产量降低，以及输送到海底的有机物质减少，这将限制春季和夏季浮游动物的次级生产。模型预测，低水平的牡蛎恢复在春季没有效果，但确实会导致夏季浮游植物存量减少。这两种作用都会对浮游动物的次级生产产生负面影响，但牡蛎恢复的预测影响更大。牡蛎对浮游植物的影响较小是由于过滤效率的大小差异和季节性差异导致，在浮游植物已经受到大量摄食的情况下，牡蛎对浮游植物的最大控制作用发生在浮游动物摄食的高峰期。这些结果表明，牡蛎恢复必须达到目前生物量的 25 倍以上，才能对浮游植物生物量产生有意义的影响，达到与 50%营养负荷减少相似的效果。在这些水平上牡蛎恢复对其他消费者的意外影响代表了对逆转富营养化的期望效果的权衡。
