SPATIAL HETEROGENEITY OF ORGANIC AND INORGANIC CARBON FROM SURFACE WATERS ON EOGENETIC CARBONATE ISLANDS—SAN SALVADOR ISLAND, BAHAMAS
Samples were collected over a three-day period in January 2016. In this abstract, we consider measurements of non-purgeable organic carbon (NPOC), dissolved inorganic carbon (DIC), specific ultraviolet absorbance (SUVA), and the stable isotopes of carbon (d13C). DIC concentrations ranged from 3.4–5.1 mM/L. Values of d13C were largely depleted in the heavier isotopes (min = -10.3‰), except for Little Lake with a positive d13C of +1.3‰. Respiration of organic matter likely influences the water chemistry at all sites. For example, excluding Inkwell and the unnamed ponds, d13C is inversely proportional to DIC; organic respiration leads to additional DIC. Additionally, NPOC ranged from 1.8–5.0 mM/L and is directly correlated to DIC; waters with greater concentrations of organic carbon undergo enhanced respiration. This is supported by an inverse relationship between NPOC and d13C. SUVA values ranged from 0.1–1.3 and is directly proportional to NPOC; surface waters with more concentrated organic carbon are less degraded and thus closer to their source. Finally, an inverse relationship between d13C and SUVA suggests that waters with more concentrated and ‘fresher’ organic matter are experiencing the greatest rates of respiration.