School of Biology, Georgia Institute of Technology, Atlanta, Georgia, United States of America.
PLoS One. 2010 Jan 29;5(1):e8963. doi: 10.1371/journal.pone.0008963.
Herbivory is an important top-down force on coral reefs that regulates macroalgal abundance, mediates competitive interactions between macroalgae and corals, and provides resilience following disturbances such as hurricanes and coral bleaching. However, reductions in herbivore diversity and abundance via disease or over-fishing may harm corals directly and may indirectly increase coral susceptibility to other disturbances.
In two experiments over two years, we enclosed equivalent densities and masses of either single-species or mixed-species of herbivorous fishes in replicate, 4 m(2) cages at a depth of 17 m on a reef in the Florida Keys, USA to evaluate the effects of herbivore identity and species richness on colonization and development of macroalgal communities and the cascading effects of algae on coral growth. In Year 1, we used the redband parrotfish (Sparisoma aurofrenatum) and the ocean surgeonfish (Acanthurus bahianus); in Year 2, we used the redband parrotfish and the princess parrotfish (Scarus taeniopterus). On new substrates, rapid grazing by ocean surgeonfish and princess parrotfish kept communities in an early successional stage dominated by short, filamentous algae and crustose coralline algae that did not suppress coral growth. In contrast, feeding by redband parrotfish allowed an accumulation of tall filaments and later successional macroalgae that suppressed coral growth. These patterns contrast with patterns from established communities not undergoing primary succession; on established substrates redband parrotfish significantly reduced upright macroalgal cover while ocean surgeonfish and princess parrotfish allowed significant increases in late successional macroalgae.
This study further highlights the importance of biodiversity in affecting ecosystem function in that different species of herbivorous fishes had very different impacts on reef communities depending on the developmental stage of the community. The species-specific effects of herbivorous fishes suggest that a species-rich herbivore fauna can be critical in providing the resilience that reefs need for recovery from common disturbances such as coral bleaching and storm damage.
食草动物是珊瑚礁的重要自上而下的力量，它调节大型藻类的丰度，调节大型藻类和珊瑚之间的竞争相互作用，并在飓风和珊瑚白化等干扰后提供恢复力。然而，通过疾病或过度捕捞导致食草动物多样性和丰度减少，可能直接伤害珊瑚，并可能间接增加珊瑚对其他干扰的敏感性。
在两年的两项实验中，我们在佛罗里达群岛的一个 17 米深的珊瑚礁上，用重复的、4 平方米的笼子，将单一物种或混合物种的食草鱼类的密度和质量等量包围起来，以评估食草动物身份和物种丰富度对大型藻类群落的定殖和发展的影响，以及藻类对珊瑚生长的级联效应。在第一年，我们使用红带鹦嘴鱼（Sparisoma aurofrenatum）和海洋医生鱼（Acanthurus bahianus）；在第二年，我们使用红带鹦嘴鱼和公主鹦嘴鱼（Scarus taeniopterus）。在新的基质上，海洋医生鱼和公主鹦嘴鱼的快速摄食使群落处于早期演替阶段，以短而丝状的藻类和壳状珊瑚藻为主，这些藻类不会抑制珊瑚生长。相比之下，红带鹦嘴鱼的摄食导致高大的丝状藻类和后来的演替大型藻类的积累，从而抑制了珊瑚的生长。这些模式与不经历初级演替的已建立群落的模式形成对比；在已建立的基质上，红带鹦嘴鱼显著减少了直立大型藻类的覆盖率，而海洋医生鱼和公主鹦嘴鱼则允许后来演替的大型藻类显著增加。
这项研究进一步强调了生物多样性在影响生态系统功能方面的重要性，即不同种类的食草鱼类对珊瑚礁群落有非常不同的影响，这取决于群落的发育阶段。食草鱼类的种特异性影响表明，丰富的食草动物群落在为珊瑚礁从珊瑚白化和风暴破坏等常见干扰中恢复提供所需的恢复力方面至关重要。
