Evaluation of Nearshore Carbonate Chemistry Within Major Navigational Inlets of the Southeast Florida Coral Reef Ecosystem Conservation Area

The absorption of atmospheric carbon dioxide (CO₂) by ocean surface water is causing ocean acidification (OA), a process by which the reaction between water and CO₂ changes ocean carbonate chemistry. While predictions of future OA impacts modeled by the Intergovernmental Panel on Climate Change (IPCC) are valuable, they may not accurately predict changes to nearshore ecosystems which experience intense variability. The dynamic nature of nearshore ocean chemistry and prevalence of OA vulnerable species and ecosystems within its boundaries complicates the process of making accurate OA impact predictions within the coastal zone. The Florida reef tract is a nearshore ecosystem vulnerable to the effects of OA, whose chemistry dynamics are influenced by the anthropogenically polluted and environmentally modified effluent carried out of its nearby inlets and waterways. Field samples collected in this investigation provide spatiotemporal data from nine navigational inlets and five wastewater outfalls affecting the nearshore carbonate chemistry dynamics of the northern Florida reef tract over the course of a year. Several notable trends have been identified involving the carbonate system and associated environmental conditions. The concentrations of solutes in the freshwater endmembers were predicted through linear regressions with salinity and indicate that all inlets and outfalls within our sample region export greater amounts of inorganic carbon compared to alkalinity. The low ratio of alkalinity to dissolved inorganic carbon indicate that freshwater mixing will exacerbate ocean acidification in the nearshore coasts of South Florida. Furthermore, there was a trend between biogeochemical properties of the inlets with latitude, indicating diverse drivers of carbon chemistry related to fundamental differences in the way the inlets function. These results are intended to inform local and regional environmental management strategies with current and accurate carbonate chemistry measurements and may serve as environmental baselines by which future impact assessments may compare against. Regional environmental management plans should remain conscious of the growing threat OA poses on its nearby natural resources.