Discharge waters from a power plant as an influent of phytoplankton in adjacent estuarine waters.

The effects of Houston Lighting and Power Company's Cedar Bayou Generating Station on phytoplankton were investigated during the period from January 1976 through January 1977. Measurements of chlorophyll a concentrations and primary productivity rates and counts of numerically dominant phytoplankton were made from samples collected monthly at ten stations. Stations were set up to monitor intake and discharge of waters of the power plant, adjacent Trinity Bay waters receiving power plants effluents, and waters at a control station in Trinity Bay near Smith Point. Bioassays were conducted with water samples from the 10 stations mentioned above to determine the suitability of water for the growth of natural mixed phytoplankton populations and Skeletonema costatum, a cultured diatom. Measurements of surface water temperature, salinity, and pH were made monthly at each station. The chlorophyll a concentrations in samples from the discharge outfall area in Trinity Bay were significantly higher than in samples from the control station. No overall effects of power plant operations on primary productivity rates were detected, but primary productivity rates varied significantly between the two intake water sources. Primary productivity was higher in samples from lower Cedar Bayou intake waters than those from upper Cedar Bayou intake waters. Assimilation numbers calculated from chlorophyll a and C14 uptake data indicated no significant variations among the areas sampled. The diatom, Coscinodiscus pygmaeus var. micropunctatus was the most frequently dominant phytoplankton species. It occurred in samples from at least one station during 6 of the 9 months that species counts were made. Dominance by blue-green algae species was noted in the study area during the warmer months, but the occurrence of these species could not be associated with the heated discharge of the power plant. Bioassay results indicated that sample water from a station at the discharge outfall into Trinity Bay and from a station 500 m from the outfall in Trinity Bay was more suitable for the growth of natural phytoplankton populations and Skeletonema costatum than sample water from the control station. Water suitability for the growth of natural phytoplankton populations was similar for samples from the intake, discharge, and discharge outfall areas. The similarity in water quality of these areas indicated that no substantial alterations in water quality for phytoplankton growth resulted from power plant operations.