Assessing ecosystem integrity of restored prairie wetlands from species production-diversity relationships

We assessed ecosystem integrity in restored prairie wetlands in eastern Sou th Dakota, U.S.A., by examining the relationship between and diatom diversi ty and production. We asked three questions: (1) Is production related to s pecies diversity? (2) Can production-diversity relationships be used to dis tinguish between restored and reference wetlands with the purpose of assess ing ecological integrity? (3) Are production-diversity relationships influe nced by species composition? Eight undisturbed, unrestored wetlands were ch osen as references to compare to eight wetlands restored after drainage. Di atoms were collected from artificial substrates that allowed communities to be transplanted from restored to reference wetlands and visa versa. Produc tion was measured as total cell biovolume and diversity as species richness . Neither diversity nor production alone differed between restored and refe rence wetlands. However, production was negatively related to diversity at restored wetlands, whereas production at reference wetlands was not. Commun ities transplanted from reference to restored wetlands exhibited a producti on-diversity relationship like that observed among control samples in resto red wetlands. Likewise, communities transplanted from restored to reference wetlands apparently lost any such relationship after they were relocated. Production was dependent on species composition. Furthermore, production of some species differed by restored and reference wetland type. The negative relationship observed between diversity and production was strongly influe nced by Rhopalodia gibba and Epithemia species, suggesting that these speci es were superior competitors under the conditions found in some restored we tlands. We consider restored wetlands displaying the highest production:div ersity ratio to be the most impaired sites, based on the extreme deviation from reference wetlands. We conclude that the relationships between diversi ty and production provided a rapid measure of restored wetland integrity wi th respect to baseline conditions observed in reference sites.