The development and application of mean trophic rank (MTR)

Abstract

For many decades macro-invertebrates have been used to assess water quality, with the Trent Biotic Index being one of the earliest developed in the UK. Whilst such biological monitoring of rivers has a long history, it is only relatively recently that the use of macrophytes has been added to the suite of existing systems. To help the UK implement the European Union's Urban Wastewater Directive, the Mean Trophic Rank (MTR) was developed. Like many of the biological quality indices based on macro-invertebrates, macrophyte species are assigned a Species Trophic Rank (STR) of 1-10, depending on their tolerance to eutrophication. Assessing the water quality at a site requires recording the abundance of species on a checklist as this affects the water quality score. Initially the MTR system was used in the UK to assess differences in nutrient status upstream and downstream of sewage discharges, but it has since been developed to be applied to detecting diffuse sources of enrichment from agricultural and other land-uses in catchments. A system has also been developed to identify potential stresses on macrophytes resulting from abstraction. Use of the method in several other European countries has resulted in a slightly modified system being adopted in Poland where the checklist of taxa has been modified to reflect the species present there. With macrophytes being an integral part of the ecological status assessment for implementing the Water Framework Directive, the MTR method is set to have wider applications in both the UK and mainland Europe. © Springer Science+Business Media B.V. 2010.