The combined effects of treated sewage discharge and land use on rivers

Freshwater ecosystems are increasingly threatened by multiple anthropogenic stressors. Release of treated sewage effluent and pollution from agricultural or urban sources can independently reduce water quality with implications for ecological communities. However, our knowledge of the combined effects of these stressors is limited. We performed a field study to quantify the combined effect of treated sewage discharge and land use on nutrient concentrations, sewage fungus presence, and communities of macroinvertebrates and benthic algae. Over three seasons in four rivers we found that a model which included an interaction between sewage pollution and time of the year (i.e., months) was the best predictor of nutrient concentrations and the abundance of algae and sewage fungus. Both macroinvertebrate and algae communities shifted downstream of sewage input. Specifically, more tolerant groups, such as cyanobacteria and Oligochaetes, were more abundant. The EPT (Ephemeroptera, Plecoptera, an..., The study was conducted during three sampling campaigns in 2021 at four rivers in the UK. Two areas were sampled at each river: 5-10 meters upstream (controls) and 5-10 meters downstream (impacts) of sewage discharge points. Nutrient analysis and sewage fungus estimation were performed on collected water samples. Benthic algae biomass was quantified using BenthoTorch. Macroinvertebrates were collected using Surber samples and identified in the lab. Land cover classification used Sentinel-2 satellite data through Google Earth Engine, distinguishing \"agriculture\" and \"urbanisation\" types.
Water samples from upstream and downstream areas were collected on each occasion to collect sewage fungus. Nutrient concentrations (nitrate, phosphate, chloride, sulfate) were analysed, and sewage fungus abundance was enumerated using preserved samples using a FlowCam machine.
Benthic algae biomass was measured using BenthoTorch on rocks collected from streams. Macroinvertebrates were collected using Sur..., R studio was used to perform all the statistical analysis and to create the graphs.,