Table 4.21. Monthly relative abundance of benthic marine algae near the Calcasieu River jetty (Kapraun 1974). 



Month 



4.10.2 CONSUMERS 



Zooplankton populations in the nearshore Gulf 

 habitat were studied by Bouchard and Turner (1976) 

 off Bay Champagne in southeastern Louisiana. A taxo- 

 nomic listing is shown in appendix 6.3. According to 

 these workers, salinity is a major influence in species 

 distribution. Calanoid copepods, particularly Acartia 

 tonsa, are the dominant zooplankton in saline and 

 brackish water, Bouchard and Turner's study covered 

 the period from October to March only, so seasonal 

 differences are not clear; but in another study (Gilles- 

 pie 1971), peak abundance of zooplankton was found 

 to occur in coastal waters in April, August, and 

 September (tig. 4-37). 



Zooplankton abundance generally follows the 

 cyclic pattern of phytoplankton abundance; however, 

 zooplankton peaks lag behind those of phytoplank- 

 ton by about one month. This lag is expected since 

 zooplankton depend heavily upon phytoplankton for 

 food. 



Penaeid shrimp dominate the nektonic inverte- 

 brate macrofauna throughout the summer, fall, and 

 winter. Five species of penaeid shrimp are commonly 

 found.but white and brown shrimp are by far the most 



abundant. In addition, several non-penaeid shrimp 

 and several species of crab are common (table 4.22). 



Benthos collected with a grab sampler along the 

 southeastern Louisiana coast were dominated by poly- 

 chaetes (fig. 4-38) on all collecting dates except in 

 December (Ragan 1976). Population density seems to 

 decrease with water depth (fig. 4-39). A taxonomic 

 list of benthos described by Ragan (1976) is included 

 in appendix 6.3. 



Excluding fish, vertebrate species richness is 

 lowest in the nearshore Gulf habitat. There are no 

 amphibians, and the reptiles are represented by sparse 

 populations of four species of sea turtles. Two of 

 these, the Atlantic hawksbill and the Atlantic logger- 

 head, are on the endangered species list. Birds using 

 the nearshore Gulf habitat are primarily fish-eating 

 species. There are often very large concentrations of 

 overwintering lesser scaup in the immediate offshore 

 area. The only mammal which regularly occurs in 

 the nearshore Gulf habitat is the Atlantic bottlenosed 

 dolphin. Although there are records of other dolphins 

 and whales from the Gulf, most of these mammals are 

 found in deep water. 



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