Assessing the extent and relative risk of aquatic stressors on stream macroinvertebrate assemblages in the neotropical savanna

作者：Silva Deborah R O^*; Herlihy Alan T; Hughes Robert M; Macedo Diego R; Callisto Marcos

来源：Science of the Total Environment, 2018, 633: 179-188.

DOI：10.1016/j.scitotenv.2018.03.127

• Bioassessment
• Probabilistic survey design
• Land use
• Physical habitat
• Water quality
• Cerrado

Freshwater ecosystems are among the most threatened by human activities, influencing losses of biodiversity. To efficiently address management practices to conserve and restore those ecosystems it is important to correctly identify and quantify the severity and magnitude of anthropogenic stressors degrading freshwater biota. In this study we assessed seven stressors describing poor water quality, physical habitat alteration, and land use by means of the relative risk (RR) and relative extent (RE) approach. The RR measures the co-occurrence probability of high stressor condition and poor biological condition. The RE measures the proportion of stream length in the region in high stressor condition. To obtain accurate estimations of RR and RE we used a probabilistic survey design to select a representative sample of perennial, wadeable and accessible streams within four hydrologic units in the neotropical savanna. Results were evaluated at two spatial scales: local-within each of the four hydrologic units, and regional-all four units combined. From 143 randomly selected sites we inferred our results to a target population of 9466 km of streams. Regionally, we found turbidity, % fine sediments and % agriculture as key stressors associatedwith poor biological condition. At the local scale, we also found that % pasture and total nitrogen were key stressors of biological condition, but their extent was relatively small. By evaluating both RR and RE we conclude that reducing excess sedimentation on streambeds should be the most effective means of improving biological condition over the region. That finding should guide decision makers and land managers to better focus their efforts and resources on improving biological condition of savanna streams.

• 出版日期2018-8-15