Surface water quality of the major drainage basins of Big Thicket NationalPreserve, Texas

Surface water quality was monitored at 19 stations (2-4 week intervals) in six drainage basins of Bit: Thicket National preserve of east Texas between 1996 and 1999. The parameters monitored were temperature, dissolved oxygen , pH, conductivity, current speed, light attenuation, chlorophyll a and con centrations of ammonium, ortho-phosphate, nitrate and nitrite. The best wat er quality (low nutrients and chlorophyll a; no hypoxia) was found in the B ig Sandy Creek, Turkey Creek and Village Creek systems. Water quality in th e Neches River was also generally good except for instances of moderate alg al blooms. The: pint Island Bayou system, however, typically showed poor wa ter quality. Very low current velocities and high concentrations of nutrien ts: promoted massive spring plankton blooms (chlorophyll a in excess of 100 mug L-1) and subsequent hypoxia/anoxia (dissolved oxygen less than 5 mg L- 1). In this system, hypoxia occurred as early as April and as late as Decem ber.