Air-Sea Gas Exchange and CO2 Fluxes in a Tropical Coral Reef Lagoon

Coral reefs are found predominately in tropical and subtropical areas and are sites of active carbon cycling. Knowledge of gas transfer velocities is necessary for carbon cycle studies in coral reef environments, and past studies in these environments have used wind speed/gas exchange parameterizations intended for the open ocean. In order to determine the relationship between wind speed and gas exchange, and to assess the suitability of open ocean wind speed/gas exchange parameterizations for this environment, two He-3/SF6 tracer release experiments were conducted during two separate years in a tropical coral reef lagoon in Kaneohe Bay, Hawaii. The results show that because water depth is relatively deep in much of Kaneohe Bay, some parameterizations intended for the open ocean can be used to predict gas transfer velocities in that environment. The bay was a source of CO2 to the atmosphere during both studies, and the residence times of water in the bay during the two studies differed by a factor of two. Plain Language Summary In order to study carbon cycling in coral reef ecosystems, scientist need to know the rate at which gases move between the ocean and the atmosphere, called the gas transfer velocity. Geochemical tracers are used to investigate the relationship between wind speed and gas transfer velocity in Kaneohe Bay in Hawaii, a tropical coral reef lagoon. The study determined that relationships between wind speed and gas transfer velocity developed for the open ocean could be applied in coral reef ecosystems, if the water is sufficiently deep.