Davenport Andrew C, Anderson Todd W
Department of Biology, San Diego State University, San Diego, California 92182-4614, USA.
Ecology. 2007 Jun;88(6):1548-61. doi: 10.1890/06-0880.
It has been suggested that microcarnivorous reef fishes may play an important role in giant kelp forest communities by preventing infestations of mesograzers that could severely impact or potentially destroy recovering kelp forests after extreme disturbance events. However, these trophic linkages, specifically the direct and indirect effects of fishes on the biomass of mesograzers, grazing intensity, and the performance of giant kelp, have not been sufficiently quantified and evaluated as to their importance and in the absence of such disturbance events. We examined experimentally the effects of mesograzers on the growth and performance of giant kelp in the presence and absence of their fish predators near Santa Catalina Island, California (U.S.A.). Mesograzer biomass and grazing intensity were significantly higher when fishes were excluded from giant kelp, which in turn, lowered kelp performance. This pattern was consistent both on experimental plots of kelp as habitat isolates, and on a continuous reef. Moreover, the abundance of mesograzers was inversely related to the abundance of kelp perch among several kelp-forested reefs, suggesting that these effects can occur at larger spatial scales. Because of differences in the diet and behavior of two microcarnivorous fishes, the kelp perch and señorita, we conducted an experiment manipulating each species and its density independently to determine their separate effects on mesograzers and kelp performance. Concurrently we examined the growth and mortality of juvenile kelp. Grazing intensity decreased, estimates of kelp performance increased, and the growth of juvenile kelp increased with increasing densities of fish but with no detectable effects between fishes. Our results demonstrate that these microcarnivorous fishes have positive indirect effects on kelp performance by reducing mesograzer biomass and grazing intensity, and the early life stages of other fishes also may be important. More specifically, these fishes have a positive effect on the density of fronds of giant kelp that can result in greater recruitment success and the abundance of kelp-associated invertebrates and fishes. Indeed, this study suggests that mesograzers have the potential to be one of the most important herbivores in kelp forest ecosystems.
有人认为，微型肉食性礁鱼可能在巨型海带森林群落中发挥重要作用，它们能防止中型食草动物大量繁殖，而这些中型食草动物可能会在极端干扰事件后严重影响或潜在破坏正在恢复的海带森林。然而，这些营养联系，特别是鱼类对中型食草动物生物量、啃食强度以及巨型海带生长状况的直接和间接影响，在没有此类干扰事件的情况下，其重要性尚未得到充分量化和评估。我们在美国加利福尼亚州圣卡塔利娜岛附近，通过实验研究了在有和没有鱼类捕食者的情况下，中型食草动物对巨型海带生长和生长状况的影响。当鱼类被排除在巨型海带区域之外时，中型食草动物的生物量和啃食强度显著更高，这反过来又降低了海带的生长状况。这种模式在作为栖息地孤立区域的海带实验地块以及连续的礁石上都是一致的。此外，在几个海带森林覆盖的礁石中，中型食草动物的数量与海带鲈的数量呈负相关，这表明这些影响可能在更大的空间尺度上发生。由于两种微型肉食性鱼类——海带鲈和多带豆娘鱼在饮食和行为上存在差异，我们分别对每种鱼类及其密度进行了实验操作，以确定它们对中型食草动物和海带生长状况的单独影响。同时，我们研究了幼年海带的生长和死亡率。随着鱼类密度的增加，啃食强度降低，海带生长状况的评估指标提高，幼年海带的生长也加快，但不同鱼类之间没有可检测到的差异。我们的结果表明，这些微型肉食性鱼类通过减少中型食草动物的生物量和啃食强度，对海带生长状况产生了积极的间接影响，并且其他鱼类的早期生命阶段可能也很重要。更具体地说，这些鱼类对巨型海带叶片的密度有积极影响，这可能导致更高的补充成功率以及与海带相关的无脊椎动物和鱼类的数量增加。实际上，这项研究表明，中型食草动物有可能成为海带森林生态系统中最重要的食草动物之一。
