Testing the pressure‐specific invertebrate index (PSI) as a tool for determining ecologically relevant targets for reducing sedimentation in streams

Abstract

2. Five macro-invertebrate indices were calculated from 51 samples taken from 13 sampling locations across two neighbouring, but contrasting study catchments in spring and autumn 2010 and 2011. For four of these, Environmental Quality Indices (EQIs) were also calculated as a proportion of observed to expected (O:E) macroinvertebrate scores, which were predicted for a theoretical pristine invertebrate community using the River Invertebrate Prediction and Classification System model. Principal Component Analysis has shown a clear hydromorphological andsedimentation gradient within the two study catchments. A generalised hierarchical mixed model with site as a random factor and % fine bed sediment as a fixed factor found a significant relationship between PSI and O:E PSI and % fine bed sediment cover at reach-scale sampling resolution over a moderate gradient of impact. Lotic Index for Flow Evaluation (LIFE) scores and Ephemeroptera-Plecoptera-Trichoptera (EPT) % abundance were also related to % fine bed sediment cover. However, PSI was more strongly related to % fine bed sediment cover than either LIFE or EPT % abundance. While PSI and O:E PSI were correlated with LIFE and O:E LIFE, PSI was not correlated with EPT % abundance, which suggests a differentiated response of these metrics to multiple stressors. The relationship between PSI and other invertebrate metrics should be subjected to further testing along a pronounced gradient of multiple stressors, as our findings suggest that PSI and % fine bed sediment cover have the potential to provide simple, sensitive and effective tools for setting of 'twin' ecological and physical sedimentation targets and add additional explanatory power to the existing suite of macro-invertebrate indices.

Evaluation of a fine sediment biomonitoring tool across a wide range of temperate rivers and streams

“…Additionally, the strong statistically significant correlation between PSI and LIFE ( r s = 0.92, P < 0.01) may be due to the relationship between flow and fine sediment transport‐deposition (Matthaei, Piggott & Townsend, ). Similar correlations between PSI, LIFE and ASPT were also observed in two contrasting catchments in the south west of the United Kingdom (see: Glendell et al ., ). In contrast, a study of conservation priority habitats (woodland, agri‐environment schemes and organic farming) in the Upper Thames catchment reported a link between PSI and these land uses, with no such link for the LIFE index.…”

“…Being based on invertebrate faunal traits, such as morphological adaptations that result in either a sensitivity or tolerance to fine sediment, the PSI index is linked to ecological niche theory, which states that organisms are adapted to a specific range of environmental conditions (Hirzel & Le Lay, 2008). This sound biological basis is important for biomonitoring tools (Bonada et al, 2006), but until now, the PSI index has only been tested against observed fine sediment data in two catchments in the United Kingdom (Glendell et al, 2013). Other published applications of the PSI index have relied on inferred sediment values when evaluating the index in the United Kingdom and also in Guinea (Africa), based on assumed relationships between flow regime or land-use/habitat modification and fine sediment levels (Extence et al, 2011;Poole et al, 2013).…”

A sediment-specific family-level biomonitoring tool to identify the impacts of fine sediment in temperate rivers and streams

“…In application, most indices should be used within an Ecological Quality Index (EQI) framework, based on observed versus expected invertebrate community composition (Glendell et al, 2014a), particularly when being used for regulatory purposes. This requires a predictive model that is independent of the pressure of concern.…”

The three Rs of river ecosystem resilience: Resources, recruitment, and refugia

“…The listed indices in Tables and are a selection of generally acknowledged resilience traits or indices. Many more examples exist of specific resilience traits and trait‐based indices of specific disturbances in rivers such as drought (Chessman, ), flow intermittence (Leigh & Datry, ), floods (Poff et al, ), sedimentation (Glendell, Extence, Chadd, & Brazier, ), or pollution (Liess & Beketov, ). Here, we emphasize the application of a variety of taxonomic, phylogenetic, and functional traits, to be able to capture the prevailing mechanism.…”