Toxicity of sediments in eight urban stormwater management ponds: bioassessment by an oligochaete community metrics used in the sediment quality triad

Implemented for decades as part of the "best management practices (BMPs)' for controlling urban runoff impacts on receiving waters, storm water ponds (SMPs) have been increasingly viewed as potential habitats for urban wildlife. However, since SMPs are subject to a lot of environmental constraints, research toward assessing their ecological quality and their actual benefits as habitats for biota is needed. In this study, the sediment toxicity of eight SMPs located in Southern Ontario, Canada was assessed using the sediment quality triad (SQT) approach. Sediment samples were collected for chemical, ecotoxicological and biological analyses. An oligochaete-based index approach (Oligochaete Index of Lake Bioindication (IOBL) and percentage of pollution-sensitive species) was used as the biological endpoint and integrated into a weight-of-evidence approach to assessing the general sediment quality of the ponds. Our results showed that (i) heavy metals in the sediment and (ii) chloride concentrations in the sediment interstitial water were responsible for detrimental effects on the ecological quality of the sediments in the ponds studied. The oligochaete indices applied in this study showed value as biological endpoints to be integrated into the SQT and used for setting up sediment ecological quality goals.