The abundance and distribution of macro-invertebrates in the cooling water canal system of the P.H. Robinson Generating Station located on Galveston Bay, Texas, with emphasis on the effect of supplemental cooling towers.




Margraf, F.J.

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Texas A&M University.


Trawl collections were taken from June 1974 to September 1975 to determine the abundance, distribution and survival rate of macro-invertebrates present in the cooling-water canal system of Houston Lighting and Power Company's P.H. Robinson Generating Station. Surface and bottom, day and night collections were taken from two stations in the intake canal, two stations in the discharge canal afferent to the cooling towers and one station in the discharge canal efferent to the cooling towers. A total of 11,655 specimens of 14 species were taken in 464 collections. Abundant species included white shrimp, Penaeus setiferus; brown shrimp, P. aztecus; blue crabs, Callinectes sapidus; and the grass shrimps, Palaemonetes pugio and P. vulgaris. Catches of macro-invertebrates in the intake canal were strongly influenced by seasonal aspects of the life history and migratory patterns of each species. Most captured in the discharge canal were recruited from the intake canal via impingement on the plant's revolving intake screens and subsequent sluicing to the discharge. The number of organisms captured was dependent on their survival rates and retention times. During the summer, catches were generally quite small afferent to the cooling towers and were generally large efferent to the towers. Prior to construction of the cooling towers, catches from both areas of the canal were small during the summer. The cooling towers increased survival rates of macro-invertebrates efferent to the towers by reducing temperatures during the summer. Based on the presence or absence of live and dead individuals in the trawl collections, the estimated upper lethal temperature was 37 C for brown shrimp, 38 C for white shrimp, and 40 C for blue crab. It appears that the supplemental cooling towers have been generally effective in promoting the survival of macro-invertebrates in the heated discharge efferent to the cooling towers.


82 p., Thesis


power plants, cooling ponds, invertebrate zoology, Penaeus aztecus, brown shrimp, Penaeus setiferus, white shrimp, blue crab, Callinectes sapidus, grass shrimp, Palaemonetes pugio, Palaemonetes vulgaris, abundance, ecological distribution