Diatom communities as ecological indicators of recovery in restored prairie wetlands

Diatoms were employed to assess the recovery of northern prairie wetlands r estored after drainage. We predicted that diatom species diversity and equi tability are lower in restored wetlands than in reference wetlands and that diatom communities are similar among reference wetlands because communitie s should be relatively stable over time. Conversely, we predicted that diat om communities in restored and reference wetlands differ because species re covery after restoration may be incomplete or unattainable depending on env ironmental conditions or dispersal limits. Eight undisturbed, unrestored (r eference) wetlands were compared to eight wetlands restored after drainage. Diatom communities on artificial substrates were transplanted from restore d to reference wetlands and vice versa to test for environmental control an d dispersal limits to community composition. Species richness was similar a t restored and reference wetlands. Diversity and equitability at restored a nd reference sites were similar within a sampling period, but diversity and equitability decreased over the growing season in reference sites. Based o n multidimensional scaling analyses, restored and reference sites could not be distinguished by species composition either early or late in the season . Transplanted diatom community assemblages became similar to those in the wetlands to which they were transferred, suggesting a strong environmental control over diatom assemblages. Diatoms, as a whole, responded rapidly to environmental conditions; yet, dispersal still may limit some species' re-e stablishment, while resistance to disturbance may produce little response a mong other diatom species. Diatoms may have limited utility as ecological i ndicators in prairie wetlands because of the unique interaction between dia tom life history and the cyclic hydrology of; prairie wetlands and because diatom community structure is highly variable among reference wetlands.