ABSTRACT: Megaherbivore grazing (e.g. by turtles, and sirenians) plays a major and well-documented role in structuring seagrass meadows around the world; however, we know little about local-scale (intra- and inter-meadow) variability in megaherbivore grazing. This is surprising given that megaherbivores are highly selective eaters who may feed by targeting certain meadows, or areas within a meadow. We ran an experiment in the Great Barrier Reef to test the question: How does megaherbivory vary on a regional scale? We used megaherbivore exclusion cages in 5 meadows along a 50 km region of coastline around Gladstone in the southern Great Barrier Reef World Heritage Area to understand variability in megaherbivory between meadows. We found differences in the impacts of megaherbivore grazing on seagrass biomass and shoot heights between meadows. There were also interannual differences in grazing impacts at one meadow that had been studied previously. These differences may be due to megaherbivore population and grazing dynamics, as well as the response of seagrass to grazing pressure. Our results show that seagrass meadows grazed by megaherbivores are dynamic systems that vary on regional spatial scales as well as over time. This is important for management measures that seek to consider the seagrass-herbivore system as a whole and understand the implications of monitoring efforts based on seagrass aboveground condition.

中文翻译：

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大堡礁南部 (GBR) 海草草地绿海龟和儒艮食草动物的时空变异性

摘要：大型食草动物放牧（例如海龟和海妖）在构建世界各地的海草草甸方面发挥着重要且有据可查的作用。然而，我们对大型食草动物放牧的局部尺度（草地内和草地间）变化知之甚少。这是令人惊讶的，因为大型食草动物是具有高度选择性的食肉动物，它们可能会以某些草地或草地内的区域为目标来觅食。我们在大堡礁进行了一项实验来测试这个问题：巨型食草动物在区域范围内有何不同？我们在大堡礁世界遗产区南部格莱斯顿周围 50 公里海岸线的 5 个草地上使用了大型食草动物排除笼子，以了解草地之间大型食草动物的变异性。我们发现大型食草动物放牧对海草生物量和草甸之间的枝条高度的影响存在差异。先前研究过的一片草地的放牧影响也存在年际差异。这些差异可能是由于大型食草动物种群和放牧动态，以及海草对放牧压力的反应。我们的研究结果表明，被大型食草动物放牧的海草草甸是动态系统，在区域空间尺度上以及随着时间的推移而变化。这对于寻求将海草-食草动物系统作为一个整体考虑并了解基于海草地上条件的监测工作的影响的管理措施很重要。我们的研究结果表明，被大型食草动物放牧的海草草甸是动态系统，在区域空间尺度上以及随着时间的推移而变化。这对于寻求将海草-食草动物系统视为一个整体并了解基于海草地上条件的监测工作的影响的管理措施很重要。我们的研究结果表明，被大型食草动物放牧的海草草甸是动态系统，在区域空间尺度上以及随着时间的推移而变化。这对于寻求将海草-食草动物系统作为一个整体考虑并了解基于海草地上条件的监测工作的影响的管理措施很重要。