Award: OCE-1829993

The major goal of this project was to perform a series of comprehensive, multi-disciplinary field experiments to measure and understand the mechanisms controlling transfer of gases like carbon dioxide and oxygen between the ocean and the atmosphere in coastal and shallow water environments. Understanding of air-sea exchange in shallow environments is a critical aspect in comprehensive modeling of coastal ecosystems and subsequently for effective management of these systems.

Two field campaigns were carried out on the barrier reef flat in Kaneohe Bay, Oahu, Hawaii, including a pilot experiment in August 2019 and a full scale experiment in August 2022. Kaneohe Bay is a large tropical embayment on the east coast of the island of Oahu, Hawaii that is about 3 km wide, extending roughly 13 km alongshore. The bay features a deep (10-15 m) back-reef lagoon partly enclosed by a broad, shallow barrier reef flat (depth 1-3 m, width ~2 km).  Both experiments included an array of instruments deployed across the reef (Figure 1) including current meters, temperature, salinity, pressure, light and dissolved oxygen sensors (Figure 2). In addition, a  thermistor chain was deployed offshore. Finally, a platform was deployed on the reef flat (Figure 3) to enable atmospheric measurements.  The study also included tracer dye releases, using nontoxic Rhodamine WT fluorescent dye to measure dilution and gas exchange. The tracers were monitored over several hours from a vessel-based system.

Our analysis of the field data has shown that dissolved gas exchange is highly affected by turbulence associated with flow over the rough reef and is notably larger than that predicted from wind-driven effects. Observations of gas exchange from our pilot and full scale experiments enable new, more accurate predictions of air-sea gas exchange in shallow environments, which can have important effects on coastal ecosystems and especially on coral reefs.  These processes further have implications for study of carbonate systems in natural systems and for assessment of potential CO2 sequestration projects. This will have substantial impacts on maintaining functioning, resilient systems that have important economic and social value for coastal communities. 

Last Modified: 05/26/2025
Modified by: Eugene R Pawlak