waters near and far from large river mouths are compared. If anything, 

 areas right at the river mouth are low, probably due to the silt load. 

 Odum explains the unusually high productivity of Georgia offshore water 

 as follows: "so much organic matter is produced in the extensive 

 salt marshes and combined with so much sediment that much of the contained 

 nutrients can not be utilized within the estuary because of low light 

 penetration. When these nutrients reach the clearer waters offshore 

 they support a year-round plankton bloom (and presumably, also a 

 fishery not yet exploited)." (J.B.) 



Keywords: productivity, estuaries, coastal marsh, nutrient outwelling, 

 Georgia 



III-D-8 



Ho, C.L., and B.B. Barrett. 1975. Distribution of nutrients in Louisiana's 



coastal waters influenced by the Mississippi River. Louisiana Wildlife 



and Fisheries Commission Technical Bulletin 17. 39 pp. 



The objectives of this investigation were: (1) to determine the 

 concentration and distribution of the major available nutrients emptied 

 into the Gulf of Mexico by the Mississippi River at various discharge 

 stages; (2) to assess the importance of nutrient supply sources other 

 than the Mississippi River, especially in estuarine systems; and 

 (3) to provide basic information for future assessment of the Mississippi 

 River's impact on fisheries production in the Gulf of Mexico and estuarine 

 systems influenced by the river. 



It was found that during heavy flooding by the Mississippi River 

 throughout Louisiana's coastal areas large amounts of freshwater were 

 discharged into these areas. Salinities were diluted and large amounts 

 of land-derived inorganic nutrients and organic nitrogen were added 

 to the coastal waters. Differences in chemical composition indicated 

 that the influence of the Mississippi River on Barataria and Caminada 

 bays was limited to the lower region of these bays during the period 

 of study. Sources of freshwater and associated nutrients introduced 

 into the bays were largely runoff waters from the upper marshes via 

 connecting waterways, bayous and drainage canals. 



When the Mississippi River discharge was lowest, the entire nearshore 

 waters were dominated by nutrient -depleted seawater. Inorganic 

 nutrients and organic nitrogen in the estuaries and the adjacent 

 nearshore waters were much higher than at the river mouth during that 

 time, which indicates the importance of the marshlands as a source of 

 inorganic nutrients and organic matter to the estuaries and adjacent 

 nearshore waters. However, the estimated quantity of selected chemical 

 components discharged by the Mississippi River from January through 

 July 1973 was 28.4 billion pounds. Such vast amounts of inorganic 



115 



