Negative effects of the sea lice therapeutant emamectin benzoate at low concentrations on benthic communities around Scottish fish farms.

Emamectin benzoate is used as an in-feed treatment for the control of sea lice parasites in all of the main farmed Atlantic salmon (Salmo salar) facilities worldwide (Norway, Chile, Scotland and Canada). Investigations into its effect on non-target benthic fauna resulting from its excretion from farmed fish and uneaten feed have been limited. This paper presents the findings from a study that intended to assess the impact of emamectin benzoate on benthic fauna using a new low detection method for emamectin benzoate. Eight fish farms in the Shetland Isles, Scotland were surveyed, with sediment sampled along transects radiating from the farms analysed for benthic ecology, sediment chemistry and sediment veterinary medicine residues (analysed for emamectin benzoate and teflubenzuron). Canonical Correspondence Analysis (CCA) and Generalised Linear Mixed Modelling (GLMM) were used to assess which environmental parameters observed during the survey had the biggest effect on benthic community composition and abundance, and more specifically crustacean abundance and richness. Emamectin benzoate was found in 97% of samples, demonstrating widespread dispersion in the sediments sampled. The CCA showed that species composition was predominantly ordinated along a gradient of particle size, with a secondary axis dominated by a change in emamectin benzoate and organic carbon enrichment. Peaks in abundance of crustacean species were predicted to be organised along a gradient of emamectin benzoate concentration. The GLMM corroborated this by showing that emamectin benzoate had the strongest negative effect on total crustacean abundance and species richness, though there was some degree of collinearity with organic carbon, that had a smaller effect. Overall, this study shows that, following its use as an in-feed treatment for sea lice, emamectin benzoate residues are more widely distributed in the benthic environment than previously thought, and have a statistically significant effect on benthic ecology at the concentrations observed in this study.

Developing a multi-pollutant conceptual framework for the selection and targeting of interventions in water industry catchment management schemes.

In recent years water companies have started to adopt catchment management to reduce diffuse pollution in drinking water supply areas. The heterogeneity of catchments and the range of pollutants that must be removed to meet the EU Drinking Water Directive (98/83/EC) limits make it difficult to prioritise areas of a catchment for intervention. Thus conceptual frameworks are required that can disaggregate the components of pollutant risk and help water companies make decisions about where to target interventions in their catchments to maximum effect. This paper demonstrates the concept of generalising pollutants in the same framework by reviewing key pollutant processes within a source-mobilisation-delivery context. From this, criteria are developed (with input from water industry professionals involved in catchment management) which highlights the need for a new water industry specific conceptual framework. The new CaRPoW (Catchment Risk to Potable Water) framework uses the Source-Mobilisation-Delivery concept as modular components of risk that work at two scales, source and mobilisation at the field scale and delivery at the catchment scale. Disaggregating pollutant processes permits the main components of risk to be ascertained so that appropriate interventions can be selected. The generic structure also allows for the outputs from different pollutants to be compared so that potential multiple benefits can be identified. CaRPow provides a transferable framework that can be used by water companies to cost-effectively target interventions under current conditions or under scenarios of land use or climate change.