ABSTRACT: Herbivory is a key ecological process that often determines the composition and abundance of plants. Estimates of herbivory in seagrass meadows are typically lower than those in other vegetated coastal ecosystems, but herbivory can be intense when large herbivorous vertebrates are abundant. We surveyed rates of herbivory on 2 species of tropical seagrasses (Thalassia hemprichii and Enhalus acoroides), the abundance of herbivorous vertebrates, and the diet of 2 abundant herbivorous vertebrates (the green turtle Chelonia mydas and the rabbitfish Siganus lineatus) in lagoons adjacent to remote islands off northwestern Australia. Rates of herbivory in some deployments of tethered seagrass were more than 1000 times higher than rates of production and were among the highest recorded. Consumption exceeded production in half the deployments (9 of 18). Remote underwater video revealed that S. lineatus was the most abundant herbivore. Stomachs of S. lineatus contained mostly seagrass, and models based on stable isotopes indicated that seagrass was the primary source of nutrition. Stomach contents of C. mydas were more variable, containing seagrass and macroalgae (although the sample size was low), but models based on stable isotopes indicated that seagrass was likely the primary source of nutrition. Multiple lines of evidence suggest that the high rates of herbivory on the seagrasses T. hemprichii and E. acoroides are mainly due to direct consumption by the abundant S. lineatus, and perhaps also C. mydas. Seagrass is the primary contributor to the nutrition of both species.

中文翻译：

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兔子鱼和绿海龟在澳大利亚西北偏远海草草地上的高草食性

摘要：食草是关键的生态过程，通常决定植物的组成和丰度。海草草甸的草食性估计通常低于其他植被繁茂的沿海生态系统，但当大型草食性脊椎动物丰富时，草食性可能会很强。我们调查了2种热带海草（Thalsia hemprichii和Enhalus acoroides）的草食率，草食性脊椎动物的丰富度以及2种丰富的草食性脊椎动物的饮食（绿海龟Chelonia mydas和兔子鱼Siganus lineatus）在与澳大利亚西北部偏远岛屿相邻的泻湖中。系留海草的某些部署中的草食率比生产率高1000倍以上，是有记录以来的最高水平。在一半的部署中，消费超过了生产量（18个部署中的9个）。远程水下录像显示，S。lineatus是最丰富的草食动物。线虫的胃中主要含有海草，基于稳定同位素的模型表明海草是主要的营养来源。C. mydas的胃内容物它们的变化更大，包含海草和大型藻类（尽管样本量很小），但是基于稳定同位素的模型表明，海草可能是主要的营养来源。多种证据表明，海草T. hemprichii和E. acoroides上的高食草性主要是由于大量的S. lineatus以及C. mydas直接食用。海草是这两种物种营养的主要贡献者。