Biogeochemical changes of chemical signals in the Georgia "land-to-ocean continuum"

Major portion of this dissertation concentrated on interpreting and analyzing temporal and spatial variability of the CO2 system in the Georgia land-to-ocean continuum, which consists of Georgia marsh-influenced riverine and non-riverine estuaries and their adjacent continental shelf up to the shelf-break. Chapter 2 described an improved fiber optic pCO2 sensor based on a long pathlength liquid-core waveguide made by Teflon AF 2400. Three pronounced characteristics of the sensor are short response time, high sensitivity and long-time stability. Chapter 3 discussed the spatial and temporal variability of distributions of nitrogen nutrients in the five Georgia riverine estuaries. Estuarine nitrification and marsh denitrification are likely two major processes that modify spatial distributions of inorganic nitrogen within these estuaries. Seasonality of river discharge and temperature are apparently responsible for observed seasonal changes in distribution patterns of inorganic nitrogen. Chapter 4 examined CO2 dynamics in the South Atlantic Bight (SAB). The study found that this shelf region is a strong atmospheric CO2 source annually and an exporter of inorganic carbon to the open ocean. The carbon budget of the region indicated that the system is net heterotrophic annually. The annual CO2 source of the system to the atmosphere is likely maintained as a combined result of net heterotrophy, more intensive heating, and high discharge of inorganic carbon from coastal salt marshes. The research in Chapter 5 was centered on the seasonal variations of the CO2 system in Georgia estuary-marsh complexes. CO2 degassing and inorganic carbon export from a marsh-dominated tidal creek, the Duplin River, were quantified on a monthly basis in order to examine seasonality of marsh-estuary interaction. The study concluded that marsh export of inorganic carbon primarily supports CO2 degassing and inorganic carbon export in the marsh-dominated estuaries. Extrapolation of the Duplin River’s result to the entire SAB salt marshes indicated that marsh export of inorganic carbon likely has significant influence on the CO2 dynamics in the SAB. As a summary of carbon cycle in the Georgia “land-to-ocean continuum”, a carbon mass balance and transport model and an “extended continental shelf pump” hypothesis were presented in Chapter 6.