Benthic macrofauna community response to salinity in the San Antonio and Matagorda Bay systems, Texas

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Ehrmann, Hannah thesis.pdf (1.29 MB)

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2017-05

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Ehrmann, Hannah

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http://hdl.handle.net/1969.6/5636

Abstract

The aim of this study was to quantify the effects of salinity on ecosystem health in Matagorda and San Antonio Bay systems, using benthic macrofauna communities as biological indicators of ecosystem integrity. Benthic and discrete water quality samples were taken monthly at five stations in the San Antonio and Matagorda Bays. Benthic macrofauna community dynamics were linked to salinity to infer the effects of freshwater inflow on the estuarine biotic communities. The benthic communities were classified into two groups based on different salinity habitat zones when salinity was above or below 11. Benthic metrics were significantly correlated with salinity, one-month lag, or two-month lag salinity in all bays. Peak abundances were observed in Carancahua and San Antonio Bays when salinities were 5 and 7 respectively, and peak diversity was observed in San Antonio Bay when salinity was 4. Diversity (Hill’s N1) increased throughout the salinity gradient in Tres Palacios and San Antonio Bays, as did abundance in Tres Palacios Bay. Overall, salinity was a driving factor for these communities. There is a need for hydrological restoration in many areas, and resources for restoration have been made available by the RESTORE Act. However, only small flows may be available to be set aside to maintain ecological health. The present study gives evidence that benthic communities are supported by low salinity habitats within the upper reaches of the San Antonio and Matagorda Bay Systems.

Description

The aim of this study was to quantify the effects of salinity on ecosystem health in Matagorda and San Antonio Bay systems, using benthic macrofauna communities as biological indicators of ecosystem integrity. Benthic and discrete water quality samples were taken monthly at five stations in the San Antonio and Matagorda Bays. Benthic macrofauna community dynamics were linked to salinity to infer the effects of freshwater inflow on the estuarine biotic communities. The benthic communities were classified into two groups based on different salinity habitat zones when salinity was above or below 11. Benthic metrics were significantly correlated with salinity, one-month lag, or two-month lag salinity in all bays. Peak abundances were observed in Carancahua and San Antonio Bays when salinities were 5 and 7 respectively, and peak diversity was observed in San Antonio Bay when salinity was 4. Diversity (Hill’s N1) increased throughout the salinity gradient in Tres Palacios and San Antonio Bays, as did abundance in Tres Palacios Bay. Overall, salinity was a driving factor for these communities. There is a need for hydrological restoration in many areas, and resources for restoration have been made available by the RESTORE Act. However, only small flows may be available to be set aside to maintain ecological health. The present study gives evidence that benthic communities are supported by low salinity habitats within the upper reaches of the San Antonio and Matagorda Bay Systems.

Keywords

benthic, bioindicator, ecosystem health, inflow, macrofauna, salinity

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