The effect of climate on estuarine benthos at regional scales along the Texas coast
Hardegree, Meagan Nichol
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Climate variability plays a key role in estuary structure and function. Fresh water is delivered to estuaries as inflows driven by precipitation. The amount of precipitation an area receives could be affected by climate change. Precipitation along the Texas coast is variable from year to year and linked to the El Niño Southern Oscillation (ENSO). A previous study demonstrated decreasing long-term trends in benthos abundance and biomass in response to changes in hydrologic conditions in the Lavaca-Colorado Estuary. The purpose of this study is to investigate whether the previous findings are unique to the Lavaca-Colorado Estuary or if these effects are regional in scale. Six stations in the Lavaca-Colorado Estuary, four stations in the Guadalupe Estuary and five stations in the Nueces Estuary, representing a salinity gradient in each estuary, were sampled quarterly for benthic macrofauna and hydrography from 1986-2009. The Ocean Nino Index (ONI) was analyzed for relationships between estuarine conditions and climate. In all three estuaries, ONI was positively correlated with salinity, inflow and dissolved oxygen. Long-term declining trends in benthos abundance were found in all three estuaries; however, biomass trends varied by bay system. A second purpose was to compare infauna and epifauna trends. Epifauna data was obtained by the Texas Parks and Wildlife Department. In some of the bays, benthic abundance and biomass was positively correlated with trends in epifauna, which are potential infauna predators. Epifauna abundance and benthic abundance were correlated with bay salinity, temperature and dissolved oxygen (DO), so overall, infauna and epifauna had similar responses over time. In contrast inverse responses would be expected if epifauna preyed on infauna, so climate change appears to be the dominant driver of long-term trends in both groups.