Effects of thermal effluents from a power station on bacteria and heterotrophic nanoflagellates in coastal waters

Abstract

To investigate effects of thermal effluents from a coastal power station on bacteria and heterotrophic nanoflagellates (HNF) in adjacent coastal waters, surface distributions of bacteria and HNF and interrelations between microbial and environmental variables were studied in November 1998 and July, August and November 1999 near Hadong Power Station, Korea. In addition, manipulation experiments with treatments of high temperature (40°C; temperature in the cooling system of the power station) and additions of hypochlorite and dilution experiments of thermal effluents with intake seawaters were carried out. Water temperature in the discharge-channel was always 5 to 10°C higher than the ambient temperature, but bacterial production, HNF abundance and grazing rates on bacteria, as well as chlorophyll a concentrations, were always lower there and increased with distance from the power station. Manipulation experiments showed that addition of hypochlorite had much more deleterious effects on bacteria and HNF (95 to 98% inhibition of bacterial production and 25 to 45% decrease in HNF abundance at 0.13 ppm of residual chlorine) than high temperature (9 to 39% inhibition of bacterial production but no inhibition of HNF abundance at 40°C). Dilutions of thermal effluents from the outlet and condenser tube with intake seawater would bring < 0.03 ppm of residual chlorine, but inhibitory effects of thermal effluents on bacterial production and HNF grazing activity (23 to 69% inhibition of bacterial production and 31 to 36% inhibition of HNF grazing) were shown, indicating inhibitory potential of chlorination by-products in the discharged water on coastal microbes. Analyses of horizontal distributions of microbial variables, manipulation and dilution experiments gave consistently similar results of inhibitory effects of thermal effluents on bacteria and HNF. Our work suggests that a microbial ecological approach is useful in estimating influences of thermal pollution on microbes in aquatic environments.

Temperature effects on the heterotrophic bacteria, heterotrophic nanoflagellates, and microbial top predators of the NW Mediterranean

“…Sea surface temperatures in the Bay of Blanes (NW Mediterranean) can vary by ~10°C over the usual annual seasonal cycle (Alonso-Sáez et al 2008), and additional sources of variability may change the sea surface temperature of coastal ecosystems by several degrees Celsius in shorter periods of time, such as during extreme heat waves or in the vicinity of the thermal effluents of power stations (Choi et al 2002). In addition, global sea surface temperatures have been increasing at rates near 0.01°C yr −1 since the 1860s (Levitus et al 2000, Vargas-Yañez et al 2005, Mackenzie & Schiedek 2007, and some climatic models predict an increase in atmospheric temperatures ranging between 2.5 and 5°C in the Mediterranean region by the end of the century (Christensen et al 2007).…”

Abundance and bacterivory of heterotrophic nanoflagellates in the meromictic Lake Suigetsu, Japan

“…These HNF abundances were within the range of those in anoxic hypolimnia of stratified lakes (Bloem et al 1989, Hadas & Berman 1998, Kopylov et al 2002, Saccà et al 2008. Previous studies demonstrated that abiotic factors regulate HNF abundance (McManus & Fuhr man 1990, Choi et al 2002. Therefore, our data using Spearman's rank correlation analysis suggest salinity and temperature are the factors that affect HNF abundance in the oxic and suboxic layers, respectively, whereas no significant correlation was found between the abundances of HNF and bacteria (Table 1).…”

Thermal effects on heterotrophic processes in a coastal ecosystem adjacent to a nuclear power plant

“…Servias & Billen (1989) showed that bacteria could tolerate higher temperatures than phytoplankton near the Muse power plant. Near the Hadong power station (Korea), Choi et al (2002) demonstrated that a temperature of 40°C inhibited BP by 23 to 69%, but had no effect on heterotrophic nanoflagellates. This indicated that larger heterotrophs might endure a higher magnitude of thermal stress than phytoplankton and bacteria.…”

“…Related studies of thermal stress on planktonic activities have been conducted elsewhere, but with limited measurements. For example, Servais & Billen (1989) studied the thermal effects on primary and bacterial production, and Choi et al (2002) worked on the influence of thermal stress on the activity of heterotrophic bacterioplankton and nanoflagellates. The system characteristic CR was not analyzed in either study.…”