How Will Changes in Freshwater Inflow (Frequency versus Magnitude) Impact the Ecosystem Health of Galveston Bay?
Thronson, AM; Hsiu-Ping, L; Davis, SE; Roelke, DL; Quigg, AS
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With a rapidly expanding urban population in Texas coastal municipalities, water regulators and managers are faced with the challenge of meeting human needs, potentially by freshwater diversions, while maintaining critical freshwater inflows to estuaries to preserve their overall health. We used a flow-through boat-mounted Dataflow unit and a PHYTO-PAM (Phytoplankton Pulse Amplitude Modulated fluorometer) to map various water quality parameters and primary productivity respectively across Galveston Bay throughout 2006. Tightly gridded transects took two days to complete. An integrated GPS allowed us to reference all measurements for each variable. Discrete water samples were collected for nutrient analysis and light/dark bottle primary productivity measurements. We found complex relationships between the freshwater inflow (frequency, magnitude), water quality (temperature, salinity, dissolved organic matter, chlorophyll, nutrients) and phytoplankton responses (productivity, community structure). Spatial and temporal patterns were deconvoluted with seasonality and the magnitude of a freshwater inflow event being the two principal driving factors regulating primary productivity. Understanding these relationships will provide scientists and regulators with information to assess estuary health in Galveston Bay as well as other estuaries along the Texas coast.