content of the ocean, but little to date in estuarine areas. Since 

 primary production alone does not account for the amount of carbon 

 contained in the open sea, it may be assumed that the Gulf of Mexico 

 receives some of its carbon supply from fringing estuaries in the form 

 of detritus. These estuaries are supported by a watershed of 919,000 

 acres of marsh and open water and more than 50,000 acres of freshwater 

 swamp. 



The concentration and distribution of detritus in the coastal waters 

 of the Barataria hydrological unit were measured using organic carbon 

 analysis. Dissolved organic carbon (DOC), total organic carbon (TOC), 

 and chlorophyll a^ (Chi a_) were measured monthly from November 1972 to 

 November 1973 at stations from the upper, middle, and lower areas of 

 Caminada and Barataria bays and in the Gulf of Mexico. 



DOC was highest in the marsh areas, averaging 6.7mg/l, and decreased 

 toward the middle and lower bay where the average DOCs were 5.7mg/l 

 and 4.7mg/l, respectively. The average DOC for Gulf water was 2.6mg/l. 

 Bay levels were highest in winter and lowest in the spring, while off- 

 shore concentrations were lowest in the winter and increased toward 

 fall. TOC values closely followed those for DOC. There were three 

 TOC peaks: in winter, early spring, and late summer. The winter 

 peak corresponded to high DOC. The spring and summer peaks probably 

 represent particulate organic carbon (POC). Chi a^ was highest in the 

 bay areas and had seasonal peaks in late January and July. 



Low temperature and north and easterly winds of 6-10 mph were posi- 

 tively correlated with DOC. The winds could have stirred up the bottom 

 sediments, causing release of interstitial DOC into the water column. 

 Organic carbon concentration in the bays is controlled by seasonal 

 phenomena related to organic production and release, by water level, 

 by influx of Gulf water, and possibly by influx of river water. 



Input of primary production to an estuary originates from three 

 sources: macrophytes (marsh grass, sea grass, mangrove, and macroalgae); 

 benthic microalgae (benthic and epibenthic diatoms, dinoflagellates, 

 and filamentous algae); and phytoplankton. Although each estuary has 

 its own characteristic proportions of these three inputs, macrophytes 

 tend to be most important in shallow marsh-fringed estuaries and 

 phytoplankton least important. 



Some of the primary producers in the region studied were Spartina 

 alterni flora (the most abundant), Distichlis spicata , Juncus roemerianus , 

 Salicornia virginica , and Avicenhia germinans . ^Four genera of macrophytic 

 algae were found regularly: Bostricha and Polysiphonia in the summer 

 and Enteromorpha and Ectocarpus in the winter. Major epiphytic diatoms 

 found were Amphora , Cocconeis , Melosira , Denticula , and Nitzschia . 

 Through estimates of marsh production, with proper allowances for 

 consumption by such fauna as copepods, shrimp, oysters, and other 



110 



