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

Abstract

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 and Tricoptera) water quality score was best explained by an interaction between month and agriculture in the surrounding landscape. Overall, our results show that sewage discharge has a significant impact on water quality and benthic riverine communities, regardless of the surrounding land uses. Agricultural inputs, however, could be more important than treated sewage discharge in reducing the abundance of sensitive invertebrate taxa. We need both improvements to wastewater treatment processes and reductions in agricultural pollution to reduce threats to vulnerable freshwater communities.

Environmental Factors Shape the Differences in Biodiversity-Area Relationships in Riverine Macroinvertebrates of Two Rivers in the Tibetan Plateau in China

“…Unlike other freshwater organisms such as fish and algae, macroinvertebrates are highly sensitive to anthropogenic disturbance, and their community composition is strongly influenced by changes in river habitat and water quality. Consequently, they are often used to assess river ecological health and biodiversity [41][42][43][44]. Furthermore, spatial and temporal changes in benthic-macroinvertebrate species diversity represent the integration of ecological and evolutionary processes operating at different spatiotemporal scales [45].…”

Temporal patterns in multiple stressors shape the vulnerability of overwintering Arctic zooplankton

“…These stressors have the potential to significantly impact biodiversity, ecosystem functioning and the provision of ecosystem services (Reid et al., 2019 ; Scherrer et al., 2023 ). Recent progress has been made in understanding the combined effects of multiple stressors (Albini et al., 2023 ; Jackson et al., 2016 ). However, quantifying interactions amongst multiple stressors remains a complex challenge, representing a key problem in ecology and conservation (Dinh et al., 2021 ; Rhind, 2009 ).…”