Surrogacy in natural patterns of benthic distribution and diversity: selected taxa versus lower taxonomic resolution

Surrogates are measures that reflect species-level community patterns, but can be more easily determined. The 2 main surrogacy methods (lowering the resolution of taxonomic identifications and selection of surrogate taxonomic groups) were first developed and widely tested in pollution impact studies. The performance of surrogates in natural benthic variability studies remains largely unexplored. The aim of the present study was to test both surrogacy methods (taxonomic sufficiency and selected taxa) in predicting benthic response (both diversity and distributional patterns) to a natural disturbance gradient produced by glacial sedimentation in an Arctic fjord. There was a strong correlation between benthic diversity and distribution patterns observed at the level of species, genus, and family. Little information was lost when the organisms were identified to the order level only. Additionally, polychaetes extracted from the basic dataset and analyzed separately were good predictors of variability throughout the macrobenthic community. The species distribution and diversity patterns observed along the glacial disturbance gradient did not persist when taxonomic resolution was lowered to the class or phylum level or when only molluscs or crustaceans were analyzed. Comparison of the current results to a number of other marine benthic studies shows that the taxonomic sufficiency of families is very high and consistent across different communities, habitats, and stress-generating factors; thus, families can be recommended as a reliable measure of benthic response to environmental gradients when species identifications are not available.