Application of the Proportion of Sediment‐sensitive Invertebrates (PSI) biomonitoring index

Abstract

Sedimentation of river beds is a key pressure impacting riverine ecological communities. Research has identified the need for new approaches to help demonstrate and quantify the impacts of excessive fine-sediment deposition on benthic macroinvertebrate populations. To help meet this requirement, the Proportion of Sediment-sensitive Invertebrates (PSI) methodology was developed and has been in operational use in the United Kingdom for several years. This paper presents a number of case studies, at both national and local scales, showing how the method can be used to identify point and nonpoint fine-sediment pollution, as well as demonstrating the analysis of a national dataset to describe the relationship between PSI and a channel substrate index.A novel approach to displaying PSI data alongside local ecological and hydrological information is also presented and interpreted, to illustrate how improved understanding of biotic and abiotic relationships and interactions can be readily accomplished. Excessive fine-sediment accumulation on river beds results in impaired ecosystem health globally. The case studies and examples presented here will provide confidence that the PSI method can form the basis for evidence gathering and analysis, both within and beyond the United Kingdom. The paper concludes with an overview of the use of PSI in catchment research and management, a consideration of the relationship of the metric with other macroinvertebrate indices, and a summary of refinements recently applied to the index.

Can Macroinvertebrate Traits Be Explored and Applied in Biomonitoring Riverine Systems Draining Forested Catchments?

“…The differential distribution of traits generally indicates their value for biomonitoring. It is suggested that the trait-based approach can be further explored, with a view to developing trait-informed indices such as the proportion of sensitive invertebrate (PSI) (Extence et al, 2017) and species at risk (SPEAR) (Verberk et al, 2013) models for Afrotropical riverine systems.…”

The scope for a system-based approach to determine fine sediment targets for chalk streams

“…There also exists a number of biomonitoring indices within the UK, where the extent of fine sediment stress can be inferred from the assemblage of benthic macroinvertebrate found instream using biotic indices (e.g. Murphy et al, 2015Murphy et al, , 2017Turley et al, 2016;Extence et al, 2017). Although biomonitoring indices offer a potential way towards setting sediment targets, they lack the explicit link to the causation of elevated fine sediment loads and accumulation and thus, suitable mitigation strategies.…”

The fine sediment conundrum; quantifying, mitigating and managing the issues

“…A number of biological indices that relate the structural responses of macroinvertebrates to fine sedimentation have been proposed (e.g., Murphy et al, ; Relyea, Minshall, & Danehy, ; Turley et al, ). Extence, Chadd, England, and Naura () evaluate one such biological index, the proportion of sediment sensitive invertebrates. They demonstrate its potential application as a national screening and catchment management tool in the identification of priority areas for sediment management practices and for post‐management appraisals.…”