Meeting Abstract

P3.67  Friday, Jan. 6  Effects of Nutrient Enrichment on Competition between the algae Microdictyon marinum and the sponge Aplysina cauliformis EASSON, Cole/G*; THACKER, Robert/W; OLSON, Julie/B; SLATTERY, Marc; WILLETT, Kristie/W; GOCHFELD, Deborah/J; University of Mississippi; University of Alabama at Birmingham; University of Alabama; University of Mississippi; University of Mississippi; University of Mississippi

Coral reefs are impacted by runoff from local population centers, including nutrients from fertilizers and sewage. Previous studies have documented that increasing the nutrient load on a coral reef can lead to a phase shift from a coral-dominated to an algal-dominated system. While many species are affected by increased algal cover, one of the more important species found on Bahamian reefs is the rope sponge Aplysina cauliformis. At our study site in the Exuma Cays, Bahamas, 28% of A. cauliformis are in direct contact with the alga Microdictyon marinum. The primary goal of this study was to understand the effects of direct contact between these two species, and assess how this interaction is affected by elevated nutrient levels. In field experiments, sponges and algae were subjected to enhanced nutrient levels separately and in contact with one another in order to examine the impacts of competition and eutrophication on a number of physiological factors. The results show that nutrients positively affected the sponge’s chlorophyll concentration, but algal contact resulted in negative effects to the sponge. Nutrients had a positive effect on the algae in all experimental treatments. Understanding the effects of nutrients on interactions between reef species will help us to better understand coral reef population changes in the face of anthropogenic impacts.