Thresholds of ecosystem response to nutrient enrichment from fish aggregations.
Thresholds of ecosystem response to nutrient enrichment from fish aggregations.
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生态系统对鱼类聚集营养富集的响应阈值。
DOI：
10.1890/12-0705.1
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发表时间：
2013
期刊：
影响因子：
4.8
通讯作者：
Elizabeth W. Stoner
中科院分区：
文献类型：
--
作者：
C. Layman;Jacob E. Allgeier;L. Yeager;Elizabeth W. Stoner
生物地球化学热点可以由动物聚集通过排泄物驱动，这为初级生产者提供了限制营养的集中来源。在亚热带海草生态系统中，我们表征了与人工礁生境周围这些热点相关的生态变化阈值。我们部署了三种大小的珊瑚礁，聚集不同密度的鱼类（因此通过排泄的营养供应水平不同），并研究了反映生态系统过程的海草特征。响应随着珊瑚礁大小的变化而变化，更高的鱼类密度（在更大的珊瑚礁上）与更明显的生态阈值相关。例如，毗邻较大珊瑚礁的海草叶片P含量百分比（%P）显著高于本底浓度；较小珊瑚礁上的鱼类密度不足以支持%P的急剧转变。叶片高度是唯一以较小珊瑚礁附近的阈值为特征的变量，但较小珊瑚礁上较低的鱼类密度（因此，营养输入）不足以满足海草的奢侈营养储存。识别生态阈值中的这种复杂性对于描述生物地球化学热点在景观尺度上可能影响生态系统功能的程度至关重要。
Biogeochemical hotspots can be driven by aggregations of animals, via excretion, that provide a concentrated source of limiting nutrients for primary producers. In a subtropical seagrass ecosystem, we characterized thresholds of ecological change associated with such hotspots surrounding artificial reef habitats. We deployed reefs of three sizes to aggregate fishes at different densities (and thus different levels of nutrient supply via excretion) and examined seagrass characteristics that reflect ecosystem processes. Responses varied as a function of reef size, with higher fish densities (on larger reefs) associated with more distinct ecological thresholds. For example, adjacent to larger reefs, the percentage of P content (%P) of seagrass (Thalassia testudinum) blades was significantly higher than background concentrations; fish densities on smaller reefs were insufficient to support sharp transitions in %P. Blade height was the only variable characterized by thresholds adjacent to smaller reefs, but lower fish densities (and hence, nutrient input) on smaller reefs were not sufficient for luxury nutrient storage by seagrass. Identifying such complexities in ecological thresholds is crucial for characterizing the extent to which biogeochemical hotspots may influence ecosystem function at a landscape scale.