Department of Life Sciences, Roehampton University, London, UK.
Centre for Environment, Fisheries and Aquaculture Science, Lowestoft Laboratory, Suffolk, UK.
J Anim Ecol. 2019 Aug;88(8):1146-1157. doi: 10.1111/1365-2656.13000. Epub 2019 May 17.
Litter breakdown in the streambed is an important pathway in organic carbon cycling and energy transfer in the biosphere that is mediated by a wide range of streambed organisms. However, most research on litter breakdown to date has focused on a small fraction of the taxa that drive it (e.g. microbial vs. macroinvertebrate-mediated breakdown) and has been limited to the benthic zone (BZ). Despite the importance of the hyporheic zone (HZ) as a bioreactor, little is known about what, or who, mediates litter breakdown in this compartment and whether breakdown rates differ between the BZ and HZ. Here, we explore the relationship between litter breakdown and the variation in community structure of benthic and hyporheic communities by deploying two standardized bioassays (cotton strips and two types of commercially available tea bags) in 30 UK streams that encompass a range of environmental conditions. Then, we modelled these assays as a response of the streambed compartment and the biological features of the streambed assemblage (Prokaryota, Protozoa and Eumetazoa invertebrates) to understand the generality and efficiency of litter processing across communities. Litter breakdown was much faster in the BZ compared with the HZ (around 5 times higher for cotton strips and 1.5 times faster for the tea leaves). However, differences in litter breakdown between the BZ and the HZ were mediated by the biological features of the benthos and the hyporheos. Biomass of all the studied biotic groups, α-diversity of Eumetazoa invertebrates and metabolic diversity of Prokaryota were important predictors that were positively related to breakdown coefficients demonstrating their importance in the functioning of the streambed ecosystem. Our study uses a novel multimetric bioassay that is able to disentangle the contribution by Prokaryota, Protozoa and Eumetazoa invertebrates to litter breakdown. In doing so, our study reveals new insights into how organic matter decomposition is partitioned across biota and streambed compartments.
河床中的垃圾分解是生物圈中有机碳循环和能量转移的重要途径，它由广泛的河床生物介导。然而，迄今为止，大多数有关垃圾分解的研究都集中在驱动它的少数分类群上（例如微生物与大型无脊椎动物介导的分解），并且仅限于底栖区（BZ）。尽管潜流区（HZ）作为生物反应器非常重要，但人们对在该隔室中介导垃圾分解的物质或生物知之甚少，并且不知道 BZ 和 HZ 之间的分解速率是否存在差异。在这里，我们通过在 30 个英国溪流中部署两个标准化的生物测定法（棉条和两种类型的市售茶袋）来探索垃圾分解与底栖和潜流社区结构变化之间的关系，这些溪流涵盖了一系列环境条件。然后，我们将这些测定法建模为河床隔室以及河床生物群集的生物特征（原核生物、原生动物和后生动物无脊椎动物）的响应，以了解整个社区中垃圾处理的普遍性和效率。与 HZ 相比，BZ 中的垃圾分解速度快得多（棉条快 5 倍，茶袋快 1.5 倍）。然而，BZ 和 HZ 之间的垃圾分解差异是由底栖生物和潜流生物的生物特征介导的。所有研究的生物类群的生物量、后生动物无脊椎动物的α多样性和原核生物的代谢多样性都是重要的预测因子，它们与分解系数呈正相关，表明它们在河床生态系统的功能中很重要。我们的研究使用了一种新颖的多指标生物测定法，能够区分原核生物、原生动物和后生动物无脊椎动物对垃圾分解的贡献。通过这样做，我们的研究揭示了有关有机物分解如何在生物区系和河床隔室之间分配的新见解。
