Abstract
Dissolved Inorganic Carbon (DIC) is an important indicator of climate change and global warming. The four major species of DIC in the marine carbonate system (CO (sub 2) , H (sub 2) CO (sub 3) , HCO (sub 3) (super -) and CO (sub 3) (super 2-) ) act as major buffers in the ocean, making them integral in the study of ocean acidification. The short-lived radium isotopes ( (super 223) Ra and (super 224) Ra) can be used to track the residence times, mixing rates and transport fluxes of water and associated DIC as well as nutrients in the coastal marine environments. In this study, we used radium isotopes to track the transport of DIC and nutrients (nitrate, nitrite, nitrogen, ammonia, and orthophosphate) from the Caloosahatchee River to the Gulf of Mexico. Due to the lack of research in Southwest Florida regarding DIC and nutrients transport and several environmental problems faced by this region, it is important to identify whether the influx of nutrients and DIC from the river plume has an effect on the Gulf. Moreover, utilization of radium isotopes facilitates the development of river-gulf mixing models. We collected water samples for DIC, total alkalinity, and nutrients from 20 sites along two transects throughout the Caloosahatchee and the Gulf of Mexico. For radium isotope analysis at each site, 40 liters of water samples were collected and then gravity filtered through manganese fibers. The Mn fibers were analyzed using a Radium Delayed Coincidence Counter (Radecc) for (super 223) Ra and (super 22) 4Ra. The activities of (super 223) Ra and (super 224) Ra varied respectively from 3.2 to 40.70 dpm/100L, and 8.35 to 126.25 dpm/100L. Similarly, the concentrations of total nitrogen, total phosphorus, and DIC varied from 1.60 to 0.25 mu g/L, 94.90 to 18.05 mu g/L, and 23.28 to 26.70 mg/L, respectively. While we are still working on further lab analyses, the preliminary results show that this region of the SWFL is very spatially and temporally dynamic system. The radioisotopes showed mixed results by location, indicating that both the groundwater influx and river discharge play important role in DIC and nutrients loading in this region. Upon completion, the results from this study will help determine the importance of freshwater plume discharge in transporting DIC.
