Comparison of the planktonic diatom community and net diatom community of Neureclipsis crepuscularis.

Abstract

The caddisfly Neureclipsis crepuscularis (Polycentropodidae) filters the water column downstream of lake effluents. Although they are predaceous, algal communities commonly thrive on their nets. I analyzed the diatom communities in these nets on two branches of a river in northern Michigan, USA. The net community was compared to the local plankton community, and at least one taxon per site was significantly different (n=2, p<0.05), and the abundance of many other taxa was noticeably different. Shannon-Weiner species diversity indices supported the observed differences in taxa, and also gave an overall analysis of difference between the two study sites. The results do show a difference in diatom community composition, but we can only speculate about the mechanism of the difference. Behavioral considerations (i.e., gardening) are a possibility, but the difference can also be explained in terms of diatom morphology, net mesh size, and the ecology of the specific diatom flora. A lack of statistical power limited the thoroughness of the study, as most of the data indicated that more differences in taxa could exist. Neureclipsis crepuscularis nets have the potential to be important in lotic diatom community assessments and as bioindicators, and this unique phenomenon deserves further study.