Influence of Water Allocation and Freshwater Inflow on Oyster Production: A Hydrodynamic–Oyster Population Model for Galveston Bay,Texas, USA |
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Authors: | ERIC N POWELL JOHN M KLINCK EILEEN E HOFMANN MARGARET A McMANUS |
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Institution: | (1) Haskin Shellfish Research Laboratory, Rutgers University, 6959 Miller Ave., Port Norris, New Jersey 08349, USA, US;(2) Center for Coastal Physical Oceanography, Crittenton Hall, Old Dominion University, Norfolk, Virginia 23529, USA, US;(3) Ocean Sciences Department, University of California Santa Cruz, 1156 High St., Santa Cruz, California 95064, USA, US |
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Abstract: | A hydrodynamic–oyster population model was developed to assess the effect of changes in freshwater inflow on oyster populations
in Galveston Bay, Texas, USA. The population model includes the effects of environmental conditions, predators, and the oyster
parasite, Perkinsus marinus, on oyster populations. The hydrodynamic model includes the effects of wind stress, river runoff, tides, and oceanic exchange
on the circulation of the bay. Simulations were run for low, mean, and high freshwater inflow conditions under the present
(1993) hydrology and predicted hydrologies for 2024 and 2049 that include both changes in total freshwater inflow and diversions
of freshwater from one primary drainage basin to another.
Freshwater diversion to supply the Houston metropolitan area is predicted to negatively impact oyster production in Galveston
Bay. Fecundity and larval survivorship both decline. Mortality from Perkinsus marinus increases, but to a lesser extent. A larger negative impact in 2049 relative to 2024 originates from the larger drop in fecundity
under that hydrology. Changes in recruitment and mortality, resulting in lowered oyster abundance, occur because the bay volume
available for mixing freshwater input from the San Jacinto and Buffalo Bayou drainage basins that drain metropolitan Houston
is small in comparison to the volume of Trinity Bay that presently receives the bulk of the bay's freshwater inflow. A smaller
volume for mixing results in salinities that decline more rapidly and to a greater extent under conditions of high freshwater
discharge.
Thus, the decline in oyster abundance results from a disequilibrium between geography and salinity brought about by freshwater
diversion. Although the bay hydrology shifts, available hard substrate does not. The simulations stress the fact that it is
not just the well-appreciated reduction in freshwater inflow that can result in decreased oyster production. Changing the
location of freshwater inflow can also significantly impact the bay environment, even if the total amount of freshwater inflow
does not change. |
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Keywords: | : Oyster Estuary Channelization Salinity Freshwater inflow Larval survivorship Fecundity Perkinsus marinus |
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