Effects of different vegetative substrates on algal composition in vernal mesocosms

We investigated the response of an algal assemblage to different vegetative substrates in controlled vernal mesocosms. Litter was collected from four vascular plant communities (Deciduous Forest, Macrophyte, Old Field and Pinus stands) and the litter was used to line the benthos of the vernal mesocosms. The development and response of the algal assemblage in treatment and control mesocosms was tracked biweekly for a period of 56 days. A repeated-measure MANOVA and Bonferroni (Dunn) post-hoc test indicated that the Pinus treatment produced a significantly greater biomass than all other treatments. The Pinus treatment mesocosms had acidic (4.5–4.7) water when sampled on day 42, which continued until the completion of the study. The greatest levels of species richness and diversity were recorded from the Deciduous Forest and Old Field treatments. Algal assemblage analyses indicated that there was much overlap in community structure between various litter treatments and algae alone (no litter). Most of the vernal mesocosm treatments were dominated by the filamentous chlorophytes Mougeotia, Oedogonium and Ulothrix. These results suggest that, in this study, the vegetative litter of vernal mesocosms (with the exception of Pinus) exhibits limited independent influence on the developmental trajectories of algal communities.