Temporal variation in algal communities in an intermittent pond

We examined the algal communities in an intermittent pond in southern Ontario, Canada, at one permanently wetted site and two that dried up. Samples were collected from decomposing leaves and from the water column from ice-out in April to late August. Most of the algae present were attached forms. While there were some differences at the genus level, both temporary and permanent sites were largely dominated by filamentous chlorophytes (e.g., Oedogonium genera) immediately after ice-out. Subsequent to this early season bloom, the communities became more taxon rich, with diatoms (especially Pinnularia spp.) predominating at the permanent site, which also supported the highest diversity (30 genera). At the genus level, the community composition at the intermittent sites were subsets of that found at the permanent site. Many of these genera are known to produce a gelatinous matrix, or have a partially gelatinous structure - both advantageous to surviving drought. Using cell counts, the Cyanophyta (Cyanobacteria) appeared to be the most important community constituents; however, biovolume showed that the Chlorophyta and Bacillariophyta were the dominant groups.