PARENT SESSION
Contributed Oral Session 23: Aquatic Ecology: Plankton Communities
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 515 A, Level 5, Palais des congrès de Montréal
Changes in local conditions do not influence zooplankton community responses to immigration.
Forrest, Jessica*,1, Arnott, Shelley1, 1 Queen's University, Kingston, Ontario, Canada
ABSTRACT- Theory and experiments have shown that diversity of local communities can be influenced by local conditions and by dispersal from the surrounding region, although the relative importance of these factors is debated and likely context-dependent. Local and regional processes also have the potential to affect community variability, but this has been less studied. We conducted a two-factor mesocosm experiment with pelagic zooplankton to test the effects of a disturbance (a nutrient pulse) and dispersal (from other lakes in the region) on local community diversity and variability. We expected that nutrient addition would change local conditions and facilitate establishment of new species, and, also, that dispersal would mitigate some of the destabilizing effects of nutrient enrichment. Although increased immigration did increase species richness in both our enriched and unenriched treatments, most added species showed no evidence of population growth in the enclosures. The nutrient pulse had no significant effect on diversity, but it increased zooplankton abundance and increased the variability of several (though not all) species. Dispersal tended to increase community stability, but this effect was independent of the nutrient treatment. We conclude that community invasibility was not influenced by productivity, and, despite the relatively low diversity of our experimental zooplankton community, dispersal-limitation did not constrain its response to our applied disturbance. This indicates an unexpected resistance to change in species composition and diversity in spite of disturbance and suggests that, in our study system, changes in abundance of resident species are more important than introductions of new species in the community response to short-term environmental change.
Key words: dispersal, nutrient pulse, diversity, variability