Richness of primary producers and consumer abundance mediate epiphyte loads in a tropical seagrass system

Consumer communities play an important role in maintaining ecosystem structure and function. In seagrass systems, algal regulation by mesograzers provides a critical maintenance function which promotes seagrass productivity. Consumer communities also represent a key link in trophic energy transfer and buffer negative effects to seagrasses associated with eutrophication. Such interactions have now been well documented in literature from temperate systems, however, it is not clear if the same relationships hold in tropical systems. This study aimed to identify if the invertebrate communities within a tropical, multispecies seagrass meadow moderated epiphyte abundance under natural conditions. This was done by comparing algal abundance across two sites at Green Island, Australia. At each site, paired plots were established where the invertebrate assemblages were perturbed via insecticide manipulation, and compared to un-manipulated plots. An 89% increase in epiphyte abundance was seen after six weeks of experimental invertebrate reductions within the system. Using generalized linear mixed effects models and path analysis we found that the abundance of invertebrates was negatively correlated with epiphyte load on seagrass leaves. Habitat species richness was seen to be positively correlated with invertebrate abundance. These findings mirror those of temperate systems, suggesting this mechanism operates similarly across latitudinal gradients.The full methodology will be made available in the Open Access publication listed in the Related Publications link below.

消费者群落（consumer communities）在维持生态系统结构与功能方面发挥着关键作用。在海草生态系统中，中型牧食者（mesograzers）对藻类的调控作用是一项核心维持功能，可有效提升海草生产力。消费者群落同时是营养级能量传递的关键纽带，还能缓冲富营养化作用对海草带来的负面影响。此类种间相互作用在温带生态系统的相关研究中已有充分记载，但目前尚不清楚热带生态系统中是否存在相同的生态关联。本研究旨在探究自然条件下，热带多物种海草床内的无脊椎动物群落（invertebrate communities）是否能够调控附生藻类（epiphyte）的丰度。研究通过对比澳大利亚绿岛两处采样点的藻类丰度开展实验：在每个采样点均设置配对样地，一组通过杀虫剂处理降低无脊椎动物群落丰度以扰动其组成，另一组为未施加干预的对照样地。实验进行六周后，系统内无脊椎动物丰度降低的样地中，附生藻类丰度提升了89%。本研究采用广义线性混合效应模型（generalized linear mixed effects models）与通径分析（path analysis），发现无脊椎动物丰度与海草叶片上的附生藻类负载量呈显著负相关；栖息地物种丰富度与无脊椎动物丰度呈显著正相关。本研究结果与温带生态系统的相关发现高度一致，表明该藻类调控机制在不同纬度梯度下的运作模式相似。完整的研究方法将在下文"相关出版物"链接所指向的开源获取期刊论文中公开。