Macroinvertebrate community structure as an indicator of phosphorus enrichment in rivers

Nutrient enrichment represents one of the most important causes of detriment to river ecosystem health globally. Monitoring nutrient inputs can be particularly challenging given the spatial and temporal heterogeneity of nitrogen and phosphorus concentrations and the indirect and often lagged effects on instream communities. The objective of this paper was to explore the association between family level macroinvertebrate community data and Total Reactive Phosphorus (TRP). To achieve this, a biological index for phosphorus sensitivity (Total Reactive Phosphorus Index – TRPI) was developed and tested utilising invertebrate community and chemical data from two datasets, one consisting 88 sites across England and the other 76 sites, both sampled in spring and autumn using the same methodology between 2013 and 2015. There was a significant association between TRPI and TRP concentrations that was stronger than other biological indices of elevated phosphorus, including the TDI (diatoms) and MTR (macrophytes), currently available in the UK. Additional testing and validation are presented via local case studies, where results indicate that macroinvertebrate family sensitivity is dependent upon a range of abiotic factors including season (time of year), benthic substrate composition, altitude, and water alkalinity.