Meeting Abstract

S1-1.15  Jan. 4  Coral ensembles: their swan song, or a CaCO3phony? SEBENS, Kenneth P.; Univ. of Washington, Seattle

Corals have suffered unprecedented mortality during two decades of elevated sea surface temperature, and many more decades of human perturbation, on a global scale. The basic biology and functional morphology of corals is becoming better understood just as their populations are declining. What happens next, and is there any hope for the future of corals and coral reefs? Will there be widespread reduction in reef area, or chaotic species replacement in coral communities? Scleractinian corals use diverse resources to grow and calcify in habitats with scarce and potentially limiting resources. Species display a wide range of colony and polyp morphologies related to resource capture, water flow, and irradiance. On shallow reefs, zooxanthellae translocate more than enough photosynthate to meet metabolic demands, yet nutrients needed for tissue growth can still be scarce. In light limited reef locations, photosynthesis does not meet energetic needs. Zooplankton and other particulate material can be important sources of nutrients and energy to reef corals, and dissolved nutrient uptake can also be significant. Experimental results show that plankton capture rate can control calcification and tissue growth in several coral species; this effect is often greater than that of other known controls, such as available bicarbonate concentrations, aragonite saturation state, and water flow. Branch size and spacing, polyp size, tentacle size and shape, all affect light and particle capture and alter the local flow environment in coral aggregations. Understanding interspecific differences in morphology, and differential utilization of diverse resources, can help explain patterns of coral diversity, zonation, and abundance on reefs. Such information can be useful in interpreting changes in growth rate and survivorship, with predicted changes in habitat quality, temperature, and seawater chemistry over the next decades.