Marine Sciences Program, Department of Biological Sciences, Florida International University, 3000 NE 151st Street, North Miami, Florida 33181, USA.
Ecol Appl. 2011 Mar;21(2):343-9. doi: 10.1890/10-1339.1.
We quantified how two human impacts (overfishing and habitat fragmentation) in nearshore marine ecosystems may affect ecosystem function by altering the role of fish as nutrient vectors. We empirically quantified size-specific excretion rates of one of the most abundant fishes (gray snapper, Lutjanus griseus) in The Bahamas and combined these with surveys of fish abundance to estimate population-level excretion rates. The study was conducted across gradients of two human disturbances: overfishing and ecosystem fragmentation (estuaries bisected by roads), to evaluate how each could result in reduced population-level nutrient cycling by consumers. Mean estimated N and P excretion rates for gray snapper populations were on average 456% and 541% higher, respectively, in unfished sites. Ecosystem fragmentation resulted in significant reductions of recycling rates by snapper, with degree of creek fragmentation explaining 86% and 72% of the variance in estimated excretion for dissolved N and P, respectively. Additionally, we used nutrient limitation assays and primary producer nutrient content to provide a simple example of how marine fishery declines may affect primary production. This study provides an initial step toward integrating marine fishery declines and consumer-driven nutrient recycling to more fully understand the implications of human impacts in marine ecosystems.
我们量化了近岸海洋生态系统中的两种人为影响（过度捕捞和生境破碎化）如何通过改变鱼类作为营养载体的作用来影响生态系统功能。我们在巴哈马群岛实证量化了最丰富的鱼类之一（灰鲷，Lutjanus griseus）的特定大小的排泄率，并将这些排泄率与鱼类丰度调查相结合，以估算种群水平的排泄率。这项研究是在两种人为干扰（被道路分割的河口）的梯度上进行的，以评估每种干扰如何通过消费者导致种群水平的营养循环减少。在未捕捞的地点，灰鲷种群的平均估计氮和磷排泄率分别平均高出 456%和 541%。生境破碎化导致鲷鱼的再循环率显著降低，溪流破碎度分别解释了估计的溶解氮和磷排泄量变异的 86%和 72%。此外，我们使用养分限制测定和初级生产者养分含量提供了一个简单的例子，说明海洋渔业的减少如何影响初级生产。本研究为整合海洋渔业衰退和消费者驱动的养分再循环提供了一个初步步骤，以更全面地了解人为影响对海洋生态系统的影响。
