92 



Mississippi River delta area to a climax grade on the south Texas continental shelf. The result is a complex of 

 sediment regimes with a decrease in the silt/clay content in the nearshore regions to the west and south where 

 the percentage of sand increases (U.S. Dept. of the Interior, Minerals Management Service 1983). In general, 

 the sediment sand content decreases across the shelf. There are exceptions to this, associated mostly with 

 topographic features and the allochthonous sedimentary regime near the Mississippi River delta. 



Baker et al. (1981) studied the benthic macrofauna and Fitzhugh (1983) re-examined the polychaete fauna around 

 oil and gas platforms on the Louisiana shelf in an area extending 320 km west from the Mississippi River delta 

 in 6 to 98 m depth. Information on the benthic fauna of the inner shelf of the northwest Gulf (10 to 20 m depth) 

 is available from brine disposal monitoring studies (Harper and McKinney 1980; Weston and Gaston 1982) and 

 the Buccaneer Gas and Oil Field study (Harper et al. 1981b). The macroinfauna of the south Texas shelf is 

 described by Flint and Holland (1980), Flint (1981) and Flint and Rabalais (1981). More recently the benthic 

 fauna of the inner shelf off southeastern Louisiana has been examined by Neff et al. (1989) and Rabalais et al. 

 (in press). Polychaetes dominate the macrobenthos in all of the areas studied. Several genera {Paraprionospio, 

 Sabellides, Magelona, Mediomastus) are numerically dominant. In most of the areas studied, benthic community 

 composition closely corresponded to sediment patterns and depth zonation. Variability in the community 

 structure was attributed to spatial variability due to the patchiness of macrobenthic organisms and temporal 

 variability due to a period of larval recruitment. Hypoxic events account for significant changes in the benthic 

 community structure (Harper et al. 1981a, b; Gaston 1985; Rabalais et al., in press). 



REFERENCES 



Baker, J.H., K.T. Kimball, W.D. Jobe, J. Janousek, C.L. Howard, and P.R. Chase. 1981. Part 6, Benthic biology, 

 pp. 1-137. In CA. Bedinger, Jr., ed. Ecological Investigations of Petroleum Production Platforms in the 

 Central Gulf of Mexico. Pollutant Fate and Effects Studies, Volume I. Rept. to Bur. Land Management, 

 Contract No. AA551-CT8-17, Southwestern Research Institute, San Antonio, Texas. 



Curray, J.R. 1965. Quaternary history, continental shelves of the United States, pp. 723-735. I_n H.E. Wright 

 and G. Frey, eds. The Quaternary of the United States. Princeton University Press, Princeton, New Jersey. 



Emery, K.O. and E. Uchupi. 1972. Western North Atlantic: topography, rocks, structure, water, life, and 

 sediments. American Assoc. Petrol. Geologists, Tulsa, Oklahoma. 532 pp. 



Fitzhugh, J. K. 1983. Factors determining the distribution and abundance of polychaetous annelids on the central 

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 286 pp. 



Flint, R.W. and J.S. Holland. 1980. Benthic infaunal variability on a transect in the Gulf of Mexico. Estuar. 

 Coast Mar. Sci. 10:1-14. 



Flint, R.W. 1981. Gulf of Mexico outer continental shelf benthos: macroinfaunal environment relationships. 

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Flint, R.W. and N.N. Rabalais. 1981. Environmental studies of a marine rcosystem: south Texas Outer 

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Gaston, G.R. 1985. Effects of hypoxia on macrobenthos of the inner shelf off Cameron, Louisiana. Estuar. 

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Harper, D.E., Jr. and L.D. McKinney. 1980. Benthos, chapter 5. In R.W. Harm, Jr. and R.E. Randall, eds. 

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Harper, D.E., Jr., L.D. McKinney, R.R. Salzer, and R J. Case. 1981a. The occurrence of hypoxic bottom water 

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