Assessing wetlands and their restoration using algae

This dissertation develops a better understanding of relationship among a variety of ecological factors within wetlands, evaluates a number of valuable ecological attributes to develop indicators for wetland bioassessment and restoration, and establishes biological and environmental criteria to protect wetland ecosystems. Ecological assessment in wetlands has to develop habitat or class specific attributes to reduce the spatial and temporal variability. I first evaluated spatial and temporal variation of environmental and algal attributes among habitats within wetlands and between restored and extant wetlands in Michigan. The results indicated non-diatom algal assemblages differed among habitats, but sediment and epiphytic diatom assemblages were not significantly different. Epiphytic assemblages in the restored and extant wetlands were relatively distinct, while both sediment and phytoplankton assemblages were not as different between restored and extant wetlands. The differences in algal assemblages among habitats within wetlands and between restored and extant wetlands were related to a number of environmental characteristics, but particularly nutrients and sediment organic matter. In my study of salt marsh restoration, organic matter in sediments and the similarity of diatom species composition between paired restored and reference salt marshes increased with age of restored marshes during spring and summer. Primary production by epiphytic and sediment algae in summer showed site-specific changes and did not change consistently with marsh age. In this study, pairwise comparison of a restored marsh and a nearby reference marsh reduced regional variation among wetlands and helped identify the successional pattern of ecological development after restoration. Because nutrients were one of the most important factors regulating periphyton growth and species composition in wetlands, experimental and field surveys were conducted to determine the limiting factors in wetlands. Experiments indicated that algae were nitrogen limited and limitation was directly related to nutrient concentrations and nutrient ratios. Although individual diatom taxa responded to nutrient additions differently, the responses of indicator taxa in the nutrient bioassays were positively correlated with natural nutrient gradients among natural wetlands indicating variation in species composition among restored wetlands was related to N-limitation. Based on the establishment of a cause-effect and stressor-sponse relationships between nutrient stressors and algal attributes, I evaluated the response of a number of valued ecological attributes to nutrient stressors. The similarity in species composition to reference conditions and the number of native species decreased and trophic index calculated with species composition increased with increasing nutrient concentrations. Diatoms as indicators of wetland nutrient pollution and human disturbance were developed using paleoecological diatom assemblages to characterize reference conditions. Biological criterion was then established based on the historic trophic status indicated by diatom species composition, and a nutrient criterion to protect or restore the biological integrity of wetlands was then established from the relationship between trophic status index and nutrients. My studies indicated that algal assemblages were valuable indicators for assessing biological condition of wetlands, monitoring restoration, and diagnosing stressors.