Distribution, abundance, and species diversity of macrobenthic and meiobenthic invertebrates in relation to Houston Ship Channel pollution in upper Galveston Bay and Tabbs Bay, Texas.




Gillard, R.M.

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Texas A&M University.


Benthic collections were made with a modified Ekman dredge over a period of 18 months from August 1970 through January 1972 at 17 stations in Tabbs Bay and upper Galveston Bay, Texas. A total of 87 species, including 24 polychaete worms, 10 gastropod snails, 11 pelecypod clams, and 26 crustaceans, were collected. The total number of species, number of individuals, and the Shannon and Weaver species diversity index were used as benthic community parameters in relation to the environmental parameters of sediment composition, temperature, salinity, dissolved oxygen, seasonal, areal, and pollution effects. There was no significant community change as the southernly distance increased to 5 miles or 7,810 meters from the inflow of pollutants into upper Galveston Bay. It was hypothesized that most of the pollutants within the deep channel sediments remain in channel sediments and do not become incorporated within the sediments of the more shallow regions of the bay because of the large 10 m depth difference between these regions. A gradual rise and stabilization of salinities at approximately 20 o/oo is believed to have been responsible for a rise in the number of species and diversity index over the study period. Based on the benthic communities, the study area was divided into the following 4 areas; area 1-upper Tabbs Bay had few species, a low diversity index and inconsistently large populations of the polychaetes Streblospio benedicti. This area was apparently adversely affected by pollution from the Houston Ship Channel. Area 2-lower Tabbs Bay was dominated by the polychaete Mediomastus californiensis and had greater numbers of the oligochaete Peloscolex gabriellae than any other area. Lower salinities during periods of increased runoff reflected the inflow of Cedar Bayou waters and possibly the close proximity to Trinity Bay itself. Area 3-stations approximately 75 meters from the Houston Ship Channel had a distinctive community. Many Diopatra cuprea (polychaete) tubes acted as substrate for epifauna and other


186 p., Dissertation


ecological distribution, abundance, species diversity, benthos, marine invertebrates, channels, pollution, Ekman dredge, meiobenthos, environmental impact