Invertebrates inputs into tropical lakes, Minas Gerais, south-eastern Brazil, 2018.

Ecotones between tropical forests and lakes compose an ecosystem interconnection with a high abundance of terrestrial invertebrates, which represent an outstanding resource for the aquatic fauna. However, there is still little quantitative information on tropical forest contribution in terms of invertebrate inputs into lacustrine systems and the factors controlling this flux. To quantify the terrestrial invertebrate contribution into tropical lakes, we selected six lakes located in the Atlantic rainforest, south-eastern Brazil, and used pan traps placed in the lakeshore. We focused on total abundance, biomass, and richness of insect orders. To assess the influence of forest and lake morphometry on terrestrial invertebrate inputs into lakes, we measured the forest–lake distance and considered the morphometric characteristics of each lake.Distance from forest negatively affected the invertebrate biomass reaching the lakes. The dissimilarity across different ecotones also increased with distance from the forest. Perimeter-to-area ratio negatively affected the invertebrate abundance, suggesting that more dendritic lakes receive more invertebrates from the forest.We estimated that annually, on average 21 tons of terrestrial invertebrates fall into the studied lakes, representing a massive food resource for the aquatic ecosystem. Hence, if the distance from the forest increases due, for instance, to severe drought or deforestation, it will create an herbaceous environment unable to provide such a quantity of insects to the water ecosystems, compromising aquatic and terrestrial trophic webs dynamics.热带森林与湖泊之间的生态交错带（ecotones）构成了一类生态系统联结带，其中陆生无脊椎动物（terrestrial invertebrates）种群丰度极高，是水生动物群的优质食物资源。然而，目前关于热带森林向湖泊生态系统（lacustrine systems）输入无脊椎动物的贡献量，以及调控这一物质通量的相关因素，仍缺乏定量研究数据。为量化陆生无脊椎动物向热带湖泊的输入量，本研究选取巴西东南部大西洋雨林区域内的6个湖泊，在湖岸布设盘式诱捕器（pan traps）开展采样。研究聚焦于昆虫纲各目的总个体丰度、生物量及物种丰富度。为评估森林与湖泊形态特征对陆生无脊椎动物入湖输入的影响，本研究测量了森林与湖泊之间的距离，并考量了各湖泊的形态学参数。森林与湖泊的距离对抵达湖泊的无脊椎动物生物量存在显著负向影响；不同生态交错带的群落异质性亦随森林-湖泊距离的增加而升高。湖岸周长-面积比对无脊椎动物的个体丰度存在显著负向影响，这表明形态更呈树状分枝的湖泊能够接收更多来自森林的陆生无脊椎动物。本研究估算显示，年均共有约21吨陆生无脊椎动物沉降至本次研究的湖泊中，构成了水生生态系统的海量食物资源。因此，若因严重干旱或森林砍伐等因素导致森林与湖泊的距离增加，将形成无法向水生生态系统提供足量昆虫的草本环境，进而破坏水生与陆生食物网的动态平衡。