Date of Award

Spring 5-5-2016

Degree Type



Marine Science

First Reader

Ronald Benner

Second Reader

Yuan Shen


Dissolved organic matter (DOM) is an important source of carbon and energy for microbial food webs in estuaries. The export of DOM from estuaries to the coastal ocean influences shelf productivity and biogeochemical cycles. Chromophoric dissolved organic matter (CDOM) is an important component of the DOM pool that absorbs light, and is photoreactive. There are various optical properties of CDOM that can be used to indicate the sources of DOM, such as whether or not it is derived from terrestrial or marine environments. In this study, the sources and bioavailability of DOM were characterized in the North Inlet estuary near Georgetown, South Carolina. Samples were collected from North Inlet for a full tidal cycle during three different times of the year. Water samples were incubated in the dark for a period of 45 to 75 days to determine the bioavailability of DOM. The DOM in the incubations was degraded by bacteria and the rate of degradation was calculated by periodically sampling to incubations for the concentration of dissolved organic carbon (DOC) as well as for optical properties of CDOM. It was found that composition, concentration, and bioavailability of DOM varied considerably on both a daily and seasonal timescale in North Inlet. During periods of ebbing and low tides, there was a higher concentration of DOM and its composition had a larger component that was derived from terrestrial plants. The bioavailability of DOM was highest during low tides when there had not been much precipitation prior to sampling, indicating the DOM was primarily marsh derived. Periods of high runoff from the surrounding forested watershed exported much higher concentrations of DOM into the estuary, but this DOM was less bioavailable than the marsh derived DOM. It was also found 3 that there was a greater abundance of DOM during the summer relative to the fall and it was more terrestrially derived and bioavailable. The bioavailability of DOM in North Inlet was high when compared to other studies of DOM bioavailability in Southeastern United States estuaries and two Danish estuaries. However, the measured rate of degradation in North Inlet indicated that very little DOM is degraded while in the estuary. These findings show that the North Inlet estuary is a major source of DOM to the coastal ocean and other studies indicate the majority of its degradation occurs on the continental shelf.

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