Rapid assessment of headwater stream macroinvertebrate diversity: an evaluation of surrogates across a land-use gradient

Implementation of policies about the conservation and restoration of aquatic ecosystems' biodiversity and ecological integrity requires rapid assessment methods. The landscapes of the Carpathian Mountains, spanning an unusually steep gradient of land-use intensity from a European perspective, offer great opportunities for evaluating such methods. Focusing on the orders Ephemeroptera, Plecoptera and Trichoptera (EPT), we evaluated three approaches for assessing macroinvertebrate species richness in second and third order streams: (1) the use of data at higher taxonomic levels, (2) the use of species-level data, and (3) the use of abundance data. The number of families was a reliable indicator of species richness within EPT. Species richness of Trichoptera was strongly correlated to species richness in Ephemeroptera and Plecoptera, and thus in the EPT group as a whole, whereas species richness in Ephemeroptera and Plecoptera did not perform as well. We found little evidence for the usefulness of abundance data as a surrogate for species richness within orders, except in Plecoptera. Taxa richness in EPT was generally positively related to forest cover in the catchments and negatively related to the proportion of agricultural land. EPT taxa richness could be used to distinguish between High/Good quality classes and those of lower ecological quality according to the EU Water Framework Directive. Our results suggest that assessments focusing on the family level provide a cost-efficient alternative to species-level assessments in second and third order streams, and point at Trichoptera as a potential indicator group.