This project is to study hypoxia in a tropical embayment in Panama (Bahia del Amirante) using a combination of ongoing monitoring data, new observations, and a numerical model. The project will focus on physical processes unique to tropical systems. Hypoxia, whereby marine waters become severely depleted in oxygen content, is a widespread deleterious anthropogenic influence on estuarine and coastal waters and is increasing in coastal regions globally. Hypoxia in tropical marine systems is poorly understood and understudied, despite the important implications for tropical ecosystems which sustain important fisheries habitats and coastal biodiversity. The project will include a field campaign to observe the physical and chemical parameters of the Bay as well as a modeling component to simulate the dynamic and biogeochemical responses and interpret the observational data. The project is expected to provide new understanding of the dynamics that initiate and control hypoxia in tropical systems. The results of this project will be disseminated through presentations at scientific meetings, seminars at universities, public talks, websites, and peer-reviewed journal articles. Communication of results to the broader scientific community will include a workshop on "Understanding hypoxia in the Caribbean" to be held in Panama in the third year of the grant. This workshop will bring together researchers from throughout the Caribbean working on diverse hypoxic systems with local Panamanian researchers and other stakeholders.<br/><br/>This project includes an observational campaign and numerical simulations that will address the dynamics of hypoxia in shallow tropical systems. Physical and chemical measurements are designed to identify the important physical processes throughout the evolution of a seasonal hypoxic event in the Bay. Bahia Almirante is a tropical embayment in the Bocas del Toro region of Panama that has experienced repeated, seasonal hypoxia resulting in widespread bleaching and mortality of corals and other invertebrates. A fully-coupled physical biogeochemical model will be developed for the bay to test the dynamical understanding. The project will also leverage a historical record of weekly observations (temperature, salinity and oxygen) by the Smithsonian Tropical Research Institute (STRI) since 2010 to give historical context to our observations and to provide validation for the simulations. The physical processes regulating the ventilation of low-oxygen bottom waters in temperature coastal regions include inflow of fresh water and atmospheric fluxes, which affect density stratification, advection, and wind, wave, and tidal-driven turbulent mixing. A better understanding of the physical mechanisms and environmental conditions responsible for oxygen variability in tropical bays will yield rich insight into benthic ecology, turbulent mixing, larval connectivity, coastal hypoxia, ocean acidification and cross-shelf exchange of nutrients, pollutants, hypoxic waters.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.