Ecological Indicators (Oct 2021)
Comparative assessment of macroinvertebrate communities within three Afromontane headwater streams influenced by different land use patterns
Abstract
Headwater streams in Afromontane ecoregions harbour locally adapted aquatic communities. However, across many regions in Africa, these ecosystems and their unique aquatic biodiversity have been severely impacted by unsustainable land use practices. We tested the hypothesis that land use disturbances were the primary drivers of community dynamics by comparing spatial and temporal dynamics together with trait-environment relationships of macroinvertebrate communities in three headwater streams influenced by different land use practices. The three headwater streams were distinguished based on high conductivity, total dissolved solids and alkaline pH in the agriculture-disturbed stream, and low temperature in a stream whose riparian zone was invaded by non-native vegetation compared to a near-natural stream. Macroinvertebrate taxonomic diversity was, nevertheless, comparable among these three streams. Constrained canonical ordination revealed that seasonality was a major driver of macroinvertebrate dynamics that was reflected mostly by the abundances of six macroinvertebrate taxa (Baetis, Dicentroptelum, Afronurus, Tricorythus, Simulium and Cheumatopsyche), whereas land use contributed a small but significant difference. Trait-environment relationships reflected seasonal changes that included the importance of benthic substratum in winter, the occurrence of collector-gatherer invertebrates in spring and aerial breathing traits in summer. Land use-related traits were, nevertheless, reflected by gill respiration and grazer feeding traits represented by Afronurus in the near-natural stream, predator traits represented by Aeshna and Lestes in the invaded stream, and aerial respiration represented by Enithares, Orectogyrus and Rhagovelia in the agriculture-disturbed stream. Our results suggest that environmental variability associated with seasonality probably played a deterministic role within which land use disturbances operated. Overall, our study suggest that importance of using multiple metrics to unpack the patterns associated with land use disturbances in headwater streams.
