Measuring water motion around corals and its relationship to nutrient transfer. How water movement affects coral reef organisms: Dr. Christopher Finelli (Louisiana Universities Marine Consortium) and Dr. David Wethey (University of South Carolina).

This project represents a continuation of studies started by Dr. Wethey in 1999, and builds on results obtained last year during Aquarius Mission 9918. Studies related to nutrient pollution on Florida's reefs are of paramount importance. This mission will investigate how large scale patterns of water movement driven by ocean currents (like the Gulf Stream) and wave action (which can impact the bottom) are translated to small scale patterns (specifically turbulence) that can directly affect coral surfaces. A multiscale approach will help identify how large scale flow conditions that bring nutrients in bulk to the reef effect local conditions, and ultimately how the shapes and sizes of corals themselves influence turbulent mixing and nutrient exchange at their surfaces (microscale results).

Special, high spatial resolution, velocity sensors will be deployed at various distances off the bottom to measure water motion and turbulence at scales measured in meters and centimeters. Additionally, oxygen micro-electrodes will be used to measure properties of flow 0.5 - 5.0 millimeters above coral surfaces. Measurements will also be made to estimate how fast materials are transferred to and from corals under different flow conditions. Large spatial scale patterns will be measured using plaster models placed in a wide range of habitats around the reef; the plaster models dissolve at rates proportional to the rate of moving water around them. Small spatial scale patterns will be measured by heat transfer between the brass models of different shape and texture and the surrounding water; this technique was successfully used in 1999 and will be expanded in this mission to include more complicated models. Finally, micro-oxygen electrodes will be used to measure changes in oxygen concentration quite close to living corals as a function of flow, colony morphology, and surface texture of the corals. Taken together, the suite of measurements made during this mission will help scientists understand how materials dissolved in the water are ultimately absorbed by corals on the reef. A specific product of this project will be the development of predictive models that help us understand how reefs respond to chemicals in the water (like nutrient pollution), natural system variation (for example, upwelling events), and possibly even climate change.