Collaborative Research: Coupled Carbon and Phosphorus Cycling

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ABSTRACTOCE-0453117Although the relationship between carbon and nutrient fluxes, and the resulting elemental ratio of dominant biomass has been reasonably well-studied for planktonic systems, little is known about the extent to which carbon and different nutrient cycles are coupled in benthic ecosystems. Coral reefs are excellent examples of benthic-dominated ecosystems in which coupling of carbon and nutrient cycles, in particular phosphorus, could be very strong or very weak. Thus, the fundamental question arises of whether the kinetics of net carbon production and phosphorus assimilation by reef communities are independently forced, resulting in widely varying C:P on reefs, or whether net carbon production simply follows rates of phosphorus assimilation through the C:P ratio of the dominant biomass in a classic model of nutrient limitation. This project combines the expertise of two coral reef biogechemists from the University of Hawaii, with that of a hydrodynamicist from Stanford University, in an interdisciplinary approach to resolve this issue. Over a year-long period, carbon and phosphorus fluxes will be measured from changes in the chemical composition of seawater moving through a control volume on a reef flat on the Kaneohe Bay Barrier Reef, Hawaii. The secondary objective is to better understand the fundamental role of wave-driven currents and Stokes drift in the net transport of water across coral reefs. These results would extend knowledge gained from prior work using flumes, with their defined flow characteristics, to the field where there has only been limited data taken prior to the advent of modern instrumentation capable of resolving water flows across the control volume boundaries. The broader Impacts of this project include improving understanding of how the productivity and composition of benthic reef communities vary under different conditions and will, therefore, provide useful knowledge to agents and agencies responsible for their management as natural resources. The project will also find mutual support with an existing NOAA program for which the University of Hawaii scientists are participants that promotes and develops the exchange of technological expertise between coastal marine scientists throughout the entire Pacific region. Finally, this project will provide valuable field experience to graduate and undergraduate students at the University of Hawaii and Stanford University.