Allison Rober

Ph.D. Candidate, Michigan State University

Conference Travel Grant Type 2 (North American Benthological Society)

Algal community responses to experimental and interannual variation in hydrology in an Alaskan boreal fen

“We examined algal community structure following a flooding event at sites previously exposed to a long-term water table manipulation, including both drought (lowered water table treatment) and flooding (raised water table treatment) conditions in an Alaskan fen. After rewetting, water-column concentrations of SRP and DIN were significantly greater in the lowered water table treatment compared to control or raised water table treatments. Average algal cell density (104cells cm-2) peaked immediately following the maxima in nutrient concentrations, and was consistently higher in the lowered water table treatment (21.14 ± 2.9) compared to control (6.76 ± 1.31) or raised (8.39 ± 1.02) water table treatments. Filamentous taxa Oedogonium, Spirogyra, and Microspora composed 43-74% of the total cell density in the lowered water table treatment. Nostoc, a nitrogen-fixing cyanobacteria, was consistently more abundant in raised (11-44%) and control (5-19%) treatments but increased in the lowered water table treatment (3-33%) as nutrients declined. The observed changes in algal taxonomic composition in response to fluctuations in water table suggests that increased frequency of drought and flooding events expected with climate change may significantly alter algal structure and function in boreal wetlands.“