PARENT SESSION
Contributed Oral Session 98: Marine Ecology: Feeding Strategies and Food Webs
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 518 C, Level 5, Palais des congrès de Montréal
Different feeding strategies in healthy and bleached reef-building Hawaiian corals.
Palardy, James*,1, 2, Rodrigues, Lisa2, Grottoli, Andréa2, 1 Brown Univeristy, Providence, RI, USA2 University of Pennsylvania, Philadelphia, PA, USA
ABSTRACT- Mass coral bleaching events have occurred on a global scale throughout the world's tropical oceans, and can result in large-scale coral mortality. When bleached, corals lose their endosymbiotic zooxanthellae and their supply of of photosynthetically fixed carbon, and must rely on either energy reserves and/or heterotrophy (feeding on zooplankton) to meet their daily metabolic needs. Here, we report the effect of bleaching on feeding rates of three coral species at 1 and 6 m on a fringing reef in Kaneohe Bay, Hawaii. Experimentally bleached and healthy fragments of Porites compressa (branching, 1.2 mm polyp diameter), Porites lobata (mounding, 1.3 mm polyp diameter), and Montipora capitata (branching, 0.8 mm polyp diameter) were allowed to feed for one hour in situ, collected, and their gut contents dissected and recorded. Five pairs of bleached and healthy coral fragments from each species were exposed to naturally occurring zooplankton at ambient zooplankton concentrations. Relative to rates in healthy corals, bleached M. capitata fed 328% more, bleached P. compressa fed 37% less and bleached P. lobata feeding rates did not differ. These results were similar at both depths. Our results show that M. capitata can substantially enhance its input of fixed-carbon through heterotrophy when bleached. Evidence from a companion study shows that M. capitata rebuilds its energy reserves while still bleached. Together, these results suggest that bleached M. capitata may be able to meet its daily metabolic carbon requirements through heterotrophic input alone. Additionally, our results provide evidence that responses to bleaching events are species specific, and that coral species may increase, decrease, or not alter feeding rates in response to the loss of photosynthetically derived products during bleaching events. As such, our results suggest that corals exhibit multiple response strategies that may be used to survive stressful conditions.
Key words: coral bleaching, coral feeding, zooplankton capture, feeding strategies