The evaluation of invertebrate communities living in a river or stream is an effective method for assessing the impacts of environmental stress on the health of an aquatic ecosystem. Invertebrates that spend all or part of their lifecycle living in a river are continually exposed to changes in the volume and chemical composition of water in the river and of the structural composition of the habitat around them.
Between 2014 and 2019, the Wessex Rivers Trust (WRT) developed and delivered multiple Catchment Invertebrate Fingerprinting (CIF) studies on river catchments within the Trust working area. Catchments have included the Rivers Test and Itchen, the Hampshire Avon, and the River Meon. The aim of the project has been to identify pollution hotspots within the catchments, providing focal areas in which the Trust and partners can deliver targeted mitigation works.
The first phase of the studies comprised collection of samples by WRT staff and volunteers. Samples were collected in spring and autumn seasons using the standardised three-minute kick sample methodology and later identified to species level. Analysis of the community structure at each sample site was undertaken utilising the following five biometric indices: PSI (fine sediment), TRPI (total reactive phosphorous index), Saprobic (organic pollution), LIFE (low-flow impacts) and SPEAR (pesticide impacts), each of which is used to identify a separate water quality pressure. This provided a current baseline condition against which future monitoring could be measured. The second phase of the studies subjected historic (multiple decade) invertebrate monitoring data supplied by the Environment Agency (EA) to statistical analysis to obtain a picture of long-term change in the data. This allowed historic trends in water quality pressures to be assessed at a catchment scale.