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首页> 外文期刊>Marine ecology progress series >Trophic cascades in seagrass meadows depend on mesograzer variation in feeding rates, predation susceptibility, and abundance
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Trophic cascades in seagrass meadows depend on mesograzer variation in feeding rates, predation susceptibility, and abundance

机译：海草草甸的营养级联取决于中度放牧者摄食率，捕食敏感性和丰度的变化

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Seagrasses provide important habitat for fishes and invertebrates but are declining around the globe, often due to overgrowth by algae. One hypothesis for this overgrowth is that overfishing of top consumers has led to greater numbers of small predatory fishes that reduce the abundance of mesograzers. This trophic cascade hypothesis requires that the same species that control algal biomass are also susceptible to fish predation. While mesograzers are known to vary in their feeding rates on algae and seagrasses, much less is known about variation in predation susceptibility and how this is related to grazing abilities. For 6 common mesograzers from Bodega Harbor, California, USA, we assessed feeding rates on macroalgae (Ulva spp.), epiphytic micro-algae, and eelgrass. We then assessed predation susceptibility using juvenile cabezon Scorpae-nichthys marmoratus in tanks of eelgrass habitat with and without Ulva. We found that the fastest consumers of all 3 primary producers were the least susceptible to predation. This appeared to be due to predator avoidance strategies; fish consumed visible caprellids at a higher rate than the larger consumers, which were either better camouflaged or able to avoid predation by building tubes within the macroalgae. Using our feeding and predation rates, along with relative abundances from field surveys, we calculated the expected trophic cascade effect with and without grazer species differences. Because fish predation was skewed towards the most abundant but least important (per capita) grazers, incorporating trait variation led to a 50 to 80% reduction in expected trophic cascade effects. Examining other seagrass communities for either similar grazer species or a similar mismatch between feeding rates and predation susceptibility may improve our understanding of the variation in trophic cascade effects across systems.
机译：海草为鱼类和无脊椎动物提供了重要的栖息地，但由于藻类的过度繁殖，全球范围内的海草正在减少。这种过度增长的一个假设是，顶级消费者的过度捕捞导致了更多的小型掠食性鱼类，这些鱼类减少了中食者的数量。这种营养级联假设要求控制藻类生物量的相同物种也容易受到鱼类捕食。尽管已知中食杂食动物对藻类和海草的摄食率会有所不同，但对捕食敏感性的变化及其与放牧能力的关系知之甚少。对于来自美国加利福尼亚州博德加港的6种常见中型放牧动物，我们评估了大型藻类（Ulva spp。），附生微藻类和鳗草的摄食率。然后，我们在有或没有Ulva的鳗鱼栖息地鱼缸中使用幼稚的赤松天蝎座-nichthys marmoratus来评估捕食敏感性。我们发现，所有三个主要生产者中最快的消费者最不容易受到掠夺。这似乎是由于避免了捕食者的策略。与较大的消费者相比，鱼类消耗可见的钩rel鱼的比率更高，而较大的消费者则伪装得更好，或者能够通过在大型藻类中筑管来避免捕食。使用我们的摄食率和捕食率以及实地调查的相对丰度，我们计算了有无放牧者物种差异的预期营养级联效应。由于鱼类的捕食偏向最丰富但最不重要的（人均）放牧者，因此纳入性状变异会导致预期的营养级联效应降低50％至80％。检查其他海草群落是否存在相似的放牧者物种或摄食率与捕食敏感性之间的相似失配，可能会增进我们对整个系统的营养级联效应变化的了解。

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