Integrative assessment of ecological responses and chemical contamination of urban wastewater outfalls on soft bottom sediments of an estuarine system

Abstract

Sewage outfalls are one of the main anthropogenic impacts to coastal systems. Linking the chemical analysis in sediment, and changes in the ecological responses is one of the main tasks in ecosystem assessment for the protection of the marine environment. A three-tiered approach to evaluate the impact of the sewage of a recently built and obsolete Urban Waste Water Treatment Plants (UWWTPs) was performed. The sewage from each UWWTP differentially affected surrounding sediments. Macrobenthic community changes were influenced by the chemical composition in the sediments but also by grain size and organic matter. Abundance of the different families of the macrobenthic communities were correlated with most of the chemicals analyzed. On the contrary, toxicity bioassays were correlated with Zn and PCB concentrations but not with environmental variables. The toxicity tests linked the effect of chemical contamination on macrobenthic communities. A joint assessment of both chemical concentrations and their ecological effects is recommended.

Keywords: Benthic indicators; Galician rias; Marine pollution; Metals; Organic compounds; Sea urchin bioassay.