Abstract

Freshwater input into Texas estuaries is critical to maintaining habitat, and foraminiferal populations can provide a means for assessing the effects of natural inflow as well as mandated releases. Nueces Bay receives freshwater from the Nueces River, which enters on the southwest shore. From 2002–2007 foraminifera were sampled on a mid-bay, north-south transect at five different stations. The populations were sampled during periods of low inflow (2002), high inflow (2003), and then low/moderate inflow (2007). During low inflow, the Central Power and Lighting Plant (CPL) was in operation at the south shore, pumping heated, more saline coolant water into the bay. Salinities were nearly constant, ranging from 23–27 at the stations, population densities were low, and there was a high incidence of shell dissolution. The high-inflow samples were taken after the CPL closed and the area received abundant precipitation, with salinities in the bay varying from 12 at the south shore to 21 at the north shore. Foraminiferal abundance was 6–98× greater than it was during low inflow, and there was a low percentage of shell dissolution. With lowmoderate inflow, salinities were from 21–30, densities were somewhat higher than those observed during low inflow, and shell dissolution again increased. Statistical analysis of all three discharge periods shows that population density varies with flow regime. At low and low/moderate discharge there are pronounced density differences among the stations, with higher densities near river input. At high discharge, population density is high at each station. This study establishes the receptivity of foraminifera to relatively short-term changes in freshwater inflow, and highlights their value for monitoring the effects of inflow on biota in Texas estuaries. The unique geographic distribution of each species may be a characteristic that imparts species resilience through time.

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