Diatom communities as ecological indicators of recovery in restored prairie wetlands

Abstract

Diatoms were employed to assess the recovery of northern prairie wetlands restored after drainage. We predicted that diatom species diversity and equitability are lower in restored wetlands than in reference wetlands and that diatom communities are similar among reference wetlands because communities should be relatively stable over time. Conversely, we predicted that diatom communities in restored and reference wetlands differ because species recovery after restoration may be incomplete or unattainable depending on environmental conditions or dispersal limits. Eight undisturbed, unrestored (reference) wetlands were compared to eight wetlands restored after drainage. Diatom communities on artificial substrates were transplanted from restored to reference wetlands and vice versa to test for environmental control and dispersal limits to community composition. Species richness was similar at restored and reference wetlands. Diversity and equitability at restored and reference sites were similar within a sampling period, but diversity and equitability decreased over the growing season in reference sites. Based on 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-establishment, while resistance to disturbance may produce little response among other diatom species. Diatoms may have limited utility as ecological indicators in prairie wetlands because of the unique interaction between diatom life history and the cyclic hydrology of prairie wetlands and because diatom community structure is highly variable among reference wetlands.