A catchment scale evaluation of multiple stressor effects in headwater streams

Abstract

Mitigation activities to improve water quality and quantity in streams as well as stream management and restoration efforts are conducted in the European Union aiming to improve the chemical, physical and ecological status of streams. Headwater streams are often characterised by impairment of hydro-morphological, chemical, and ecological conditions due to multiple anthropogenic impacts. However, they are generally disregarded as water bodies for mitigation activities in the European Water Framework Directive despite their importance for supporting a higher ecological quality in higher order streams.We studied 11 headwater streams in the Hove catchment in the Copenhagen region. All sites had substantial physical habitat and water quality impairments due to anthropogenic influence (intensive agriculture, urban settlements, contaminated sites and low base-flow due to water abstraction activities in the catchment). We aimed to identify the dominating anthropogenic stressors at the catchment scale causing ecological impairment of benthic macroinvertebrate communities and provide a rank-order of importance that could help prioritising mitigation activities. We identified numerous chemical and hydromorphological impacts of which several were probably causing major ecological impairment, but we were unable to provide a robust rank-ordering of importance suggesting that targeted mitigation efforts on single anthropogenic stressors in the catchment are unlikely to have substantial effects on the ecological quality in these streams.The SPEcies At Risk (SPEAR) index explained most of the variability in the macroinvertebrate community structure, and notably, SPEAR index scores were often very low (< 10 % SPEAR abundance). An extensive re-sampling of a subset of the streams provided evidence that especially insecticides were probably essential contributors to the overall ecological impairment of these streams.Our results suggest that headwater streams should be considered in future management and mitigation plans. Catchment-based management is necessary because several anthropogenic stressors exceeded problematic thresholds, suggesting that more holistic approaches should be preferred.

Effects of neonicotinoids and fipronil on non-target invertebrates

“…Pesticide exposure was identified to strongly reduce the amount and abundance of vulnerable invertebrate species in streams using the SPEAR approach (Liess and von der Ohe 2005 ). The approach was extended from German streams to Australian, Danish, French and Finnish streams revealing the same effects of pesticide exposure on vulnerable invertebrate species (Rasmussen et al 2013 ; Liess et al 2008 ; Schäfer et al 2012 ). Beketov et al ( 2013 ) analysed the effect of pesticide presence on invertebrate species richness in European (Germany and France) and Australian streams.…”

Legacy of a Chemical Factory Site: Contaminated Groundwater Impacts Stream Macroinvertebrates

“…According to the EU Water Framework Directive (Directive 2008/105/EC), member states are obliged to assess the risk of all contaminated sites that may impact chemical and ecological quality of streams and lakes via groundwater transport. Ideally, the ecological impairment in streams caused by contaminated sites should be disentangled from the effects of other stressors, such as diffuse source pollution from agricultural and urban settings, in order to evaluate their importance (McKnight et al 2012;Rasmussen et al 2013; Roy and Bickerton 2012;Tesoriero et al 2013).…”

Pesticide risk assessment and management in a globally changing world—report from a European interdisciplinary workshop

“…However, monitoring results show that in practice, aquatic ecosystems are exposed to a cocktail of pesticides at the same time (e.g. (Beketov et al 2009 ; Rasmussen et al 2013 ). These concentrations are quite often relatively low and usually do not exceed the individual EQS or probable no-effect concentrations (PNECs).…”