The unique traits of large animals often allow them to fulfill functional roles in ecosystems that small animals cannot. However, large animals are also at greater risk from human activities. Thus, it is critical to understand how losing large animals impacts ecosystem function. In the oceans, selective fishing for large animals alters the demographics and size structure of numerous species. While the community‐wide impacts of losing large animals are a major theme in terrestrial research, the ecological consequences of removing large animals from marine ecosystems remain understudied. Here, we combine survey data from 282 sites across the Caribbean with a field experiment to investigate how altering the size structure of parrotfish populations impacts coral reef communities. We show that Caribbean‐wide, parrotfish populations are skewed toward smaller individuals, with fishes <11 cm in length comprising nearly 70% of the population in the most heavily fished locations vs. ~25% at minimally fished sites. Despite these differences in size structure, sites had similar overall parrotfish biomass. As a result, algal cover was unrelated to parrotfish biomass and instead, was negatively correlated with the density of large parrotfishes. To mechanistically explore how large parrotfishes shape benthic communities, we manipulated fishes’ access to the benthos to create three distinct fish communities with different size structure. We found that excluding large or large and medium‐sized parrotfishes did not alter overall parrotfish grazing rates but caused respective 4‐ and 10‐fold increases in algal biomass. Unexpectedly, branching corals benefited from excluding large parrotfishes whereas the growth of mounding coral species was impaired. Similarly, removing large parrotfishes led to unexpected increases in coral recruitment that were absent when both large and medium bodied fishes were excluded. Our data highlight the unique roles of large parrotfishes in driving benthic dynamics on coral reefs and suggests that diversity of size is an important component of how herbivore diversity impacts ecosystem function on reefs. This study adds to a growing body of literature revealing the ecological ramifications of removing large animals from ecosystems and sheds new light on how fishing down the size structure of parrotfish populations alters functional diversity to reshape benthic reef communities.

中文翻译：

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过度捕捞和从加勒比珊瑚礁消灭大型鹦嘴鱼的生态影响

大型动物的独特特征通常使它们能够在小型动物无法发挥的生态系统中发挥功能性作用。但是，大型动物也面临着人类活动带来的更大风险。因此，了解失去大型动物如何影响生态系统功能至关重要。在海洋中，对大型动物的选择性捕捞改变了许多物种的人口统计和大小结构。尽管失去大型动物对整个社区的影响是陆地研究的一个主要主题，但从海洋生态系统中删除大型动物的生态后果仍未得到充分研究。在这里，我们将加勒比地区282个站点的调查数据与现场实验相结合，以研究改变鹦嘴鱼种群的大小结构如何影响珊瑚礁群落。我们表明，在加勒比海地区，鹦鹉鱼的种群偏向较小的个体，长度<11厘米的鱼占捕鱼最密集地区的近70％，而捕鱼最少的地区约占25％。尽管在大小结构上存在这些差异，但站点的鹦鹉鱼生物量总体相似。结果，藻类的覆盖与鹦嘴鱼的生物量无关，而是与大型鹦嘴鱼的密度负相关。为了机械地探索大型鹦嘴鱼如何塑造底栖生物群落，我们操纵了鱼类进入底栖动物的通道，以创建三个不同大小结构的截然不同的鱼类群落。我们发现，排除大型或大型和中型鹦嘴鱼不会改变总体鹦嘴鱼的放牧率，但会导致藻类生物量分别增加4倍和10倍。不料，分支的珊瑚受益于排除大型鹦嘴鱼，而堆土珊瑚的生长受到了损害。同样，去除大型鹦嘴鱼会导致珊瑚招募的意外增加，而大中型鱼都被排除在外时，珊瑚的招募就不存在了。我们的数据强调了大型鹦嘴鱼在驱动珊瑚礁底栖动力方面的独特作用，并表明大小的多样性是草食动物多样性如何影响珊瑚礁生态系统功能的重要组成部分。这项研究增加了越来越多的文献，揭示了从生态系统中删除大型动物的生态后果，并为捕捞鹦鹉鱼种群的大小结构如何改变功能多样性以重塑底栖珊瑚礁群落提供了新的思路。