Multivariate techniques relating macroinvertebrate and environmental data from a river catchment

Macroinvertebrates were collected over 4 years by standard sampling procedures used within the UK Environment Agency (EA). Contemporary environmental data were used to “explain” biological variation using multivariate techniques provided by the program CANOCO. Variations in macroinvertebrate taxa composition, Biological Monitoring Working Party (BMWP) score and average score per taxon (ASPT) primarily reflected changes in habitat across the Mole catchment. When the analysis was restricted to sites overlying the dominant geological stratum (Weald clay) the principal variation in taxa composition, BMWP score and ASPT was most correlated with variation in water quality. Significant correlations between the presence of certain taxa and measurements of dissolved oxygen (DO) provided support for the relative scores attributed to these taxa by the BMWP. The month in which a macroinvertebrate sample was collected was relatively unimportant as an influence on taxa composition.