Wastewater Treatment Plant Influences on Macroinvertebrate Assemblage, Functional Feeding Groups, and Productivity

Park, Kelli

ABSTRACT: Organic waste from municipal wastewater treatment plants can alter stream benthic communities by contributing allochthonous energy sources as well as altering stream physicochemical habitat parameters. Nutrients may have a large impact on the primary and secondary production of receiving streams. The purpose of this study is to evaluate the impacts of wastewater treatment plant effluents on headwater systems in the Southern Appalachian Mountains. To do this the biological, physical, and chemical aspects along multiple stream continuums were analyzed. Benthic macroinvertebrates and stream physicochemical parameters were measured in 5 reference and 3 effluent-impacted streams in western North Carolina. Aquatic invertebrates were collected using a modified NCDEQ macroinvertebrate sampling protocol and keyed to the lowest possible taxonomic level. Benthic invertebrate data were used to compute community BI scores, diversity indices and the percentage of trophic feeding guilds. Water chemistry and habitat integrity were assessed at all sites. Benthic communities in impacted streams did not follow the RCC predicted feeding group distributions. In contrast benthic communities in reference streams generally followed the predictions of the RCC. However, predator abundance was generally higher than predicted in reference streams, while lower than predicted in impacted streams. Overall trends among impacted sites were variable and community structure was likely affected by increased ion concentrations, increased nutrients, and increased levels of primary production at effluent-impacted sites. Increased abundance and richness of collector-gatherers, decreased abundance of Ephemeroptera, Plecoptera and Trichoptera, an increase in Diptera taxa, and lower stream BI scores downstream from effluent outfalls were found when compared to upstream control sites. Multiple regression analyses found that temperature, discharge, conductivity, pH, and elevation variables best predicted several macroinvertebrate metrics taxa in reference streams verses impacted streams. Principal component analyses using invertebrate metrics and water chemistry parameters revealed distinctions between reference and impacted streams, and non-metric dimensional scaling plots showed that temperature, conductivity, and multiple dissolved ions significantly differentiate these sites. Implications of this study are vast and applicable to water use stakeholders, planners, and management agencies. Understanding the degree to which these types of effluent sources impact headwater streams, managers can make better decisions about permitting and placement of new facilities to protect downstream ecosystems from adverse anthropogenic impacts.