The nearshore Gulf environment is generally more 

 uniform than the inland open water environment. Sa- 

 linity varies from 10 to 35%o, depending on fresh- 

 water inflow. Water temperatures are buffered by the 

 deep oceanic waters and are more moderate than those 

 of inland waters. The stirring of the water column by 

 wave energy, the lower water temperatures in summer, 

 and the living biomass effectively maintain sufficient 

 dissolved oxygen for biological activities. 



4.10.1. PRODUCERS 



Phytoplankton studies of the Gulf of Mexico 

 nearshore region are few. Selected areas have been 

 surveyed (Freese 1952, Simmons and Thomas 1962) 

 but much more work on taxonomy, ecology, and pro- 

 ductivity needs to be done. 



In a study along the southeastern Louisiana coast, 

 Green (1976) found that the predominant species 

 during the spring to summer months consisted of the 

 dinoflagellates; Ceratium, Exuviaella, Gonyaulaux, 

 and Gymnodiyiium; the diatoms: Asterionella, Bid- 

 dulphia, Coscinodiscus, Cyclotella, Lithodesmium, 



Navicula, Pleiirosigma, Surirello, Skeletonema, Stau- 

 roneis, and Thallasiosira. In the fall and winter, 

 diatoms were the dominant phytoplankton (table 

 4.20). 



Studies of benthic marine algae in Louisiana have 

 centered on the Chandeleur Islands off the south- 

 eastern Louisiana coast. Kapraun (1974), however, 

 has conducted field and culture studies of the seasonal 

 periodicity and distribution of the benthic marine 

 algae along the Louisiana coast including the Calcasieu 

 region (table 4.21). 



Of the species observed by Kapraun, most devel- 

 oped maximum growth in winter or early spring. 

 Polysiphonia subtilissima exhibited the greatest abun- 

 dance in the summer. Giffordia m!(c/i(?//!ae, primarily 

 a tropical form, failed to develop as part of the sum- 

 mer flora; instead, it appeared inconspicuously at 

 other times of the year. Cladophora dalmatka, Ecto- 

 carpus intermedius, Enteromorpha clathrata, and E. 

 ramulosa formed extensive blooms during February 

 and March on the mudflats flanking the Calcasieu 

 River. 



Table 4.20. Collections of phytoplankton by taxa and month from nearshore Gulf 

 waters in southeastern Louisiana (Green 1976). 



Month 



Month 



208 



