Effect of Climatic Variability on Freshwater Inflow, Benthic Communities, and Secondary Production in Texas Lagoonal Estuaries: FY 2007
Montagna, Paul A.
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This is the final report for a 2-year project (TWDB contract numbers 07-483-0672 and 08-483-0791) with the objective to complete implementation of an ecological model to predict system-wide secondary production for two trophic groups of benthic organisms in response to different freshwater inflow regimes that result from the climatic ecotone along the Texas coast. The bioenergetic model was calibrated using an 11-year dataset (from 1988 to 1999) and validated with a 20-year data from (1988 to 2008) from four estuaries in South Texas: Lavaca-Colorado (LC), Guadalupe (GE), Nueces (NE) and Laguna Madre Estuaries (LM). The estuaries lie in a climatic gradient where LC and GE receive more rainfall than NE, and NE receives more rainfall than LM. Consequently inflow decreases along the gradient and salinity increases. In addition there is year-to-year variation in rain and inflow that results in wet and dry years. Therefore, this combination of the climatic gradient and temporal variability can be used to identify the effects of inflow on estuarine productivity. Among Texas estuaries, increased salinity (and thus decreased inflow) benefited deposit feeders, while suspension feeders were harmed, but the net overall effect is a decrease in functional diversity when salinity is increased. Within estuaries, the benthic community of secondary bays is harmed by reduced inflow, whereas, the community in primary bays appears to benefit in biomass increase by reduced inflow. This is because lower salinity regimes are required to support food production for suspension feeders, and there are more polyhaline deposit feeding species. Freshwater inflow is important in to maintain productivity and functional diversity; and required to maintain functional, healthy estuarine ecosystems.