Aquatic Sciences Meeting, Albuquerque 2001

PC17 Phytoplankton Physiology and Ecology

Date: Thursday, February 15, 2001

Location: Southwest Hall

Findlay, D, L, FRESHWATER INSTITUTE, WINNIPEG, Canada, FINDLAYD@DFO-MPO.GC.CA

Kasian, S, E, FRESHWATER INSTITUTE, WINNIPEG, Canada, KASIANS@DFO-MPO.GC.CA

RESPONSE OF DINOFLAGELLATES TO ACIDIFICATION AND CLIMATE INDUCED DOC DECREASE

Dinoflagellate populations from unmanipulated Lake 239 and experimentally acidified Lake 302 south (Experimental Lakes Area) were examined for responses related to decreased DOC due to climatic changes and acidification (1974-98). ELA meteorological records (1968-99) indicated the region experienced a 2° C increase in air temperature and a significant decrease in precipitation (1980-89). Lake 302S, which was subjected to this climate regime, was acidified from 1982-1992 (pH 6.8 to 4.5). During the extended drought and acidification, DOC decreased and light extinction increased in Lakes 239 and 302S. Although nutrient loading (C, N, and P) decreased during the drought there was no significant decrease observed in epilimnetic concentrations. With increased light and deepening of the euphotic zone, dinoflagellate abundances increased. However, species dominance appeared to be perturbation specific. These species are mixotrophic and capable of cycling through the deeper, less light-intense, nutrient-rich waters to consume bacteria and picoplankton as an alternative source of carbon, nitrogen and phosphorus. These species are generally large and slow growing and therefore suspended nutrients were held in the water column for a longer period of time.

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Aquatic Sciences Meeting, Albuquerque 2001

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