Natural phytoplankton collected from the Yueqing Bay was exposed to a series of heat shock temperatures and chlorine dosages in a laboratory for simulating its passage through coastal power plant cooling systems. A short-term thermal shock (30 min) had no appreciable effect on the microalgae community for temperature elevation of 4-12°C in all seasons. However, the adverse effects of chlorination on the microalgae were considerably more severe than those of a thermal shock in terms of dominant succession, species richness, diversity, evenness, and community composition. Moreover, chlorination strongly influenced the diversity indices throughout a 15-d culture period, indicating an evident lagging effect on the injured cells of entrained microalgae. The dominance of small phytoplankton species (r-strategists, e.g., Melosira moniliformis, Nitzschia longissima, and Skeletonema costatum) gradually increased during chlorine dosage range from 1.0 to 3.2 mg L-1. A typical chlorine dosage of 1-2 mg L-1 in cooling systems was found to influence the entrained subtropical phytoplankton community structure.

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