Thermal discharge-induced seawater warming alters richness, community composition and interactions of bacterioplankton assemblages in a coastal ecosystem

Despite accumulating evidence on the impact of global climate warming on marine microbes, how increasing seawater temperature influences the marine bacterioplankton communities is elusive. As temperature gradient created by thermal discharges provides a suitable in situ model to study the influence of warming on marine microorganisms, surface seawater were sampled consecutively for one year (September-2016 to August-2017) from the control (unimpacted) and thermal discharge-impacted areas of a coastal power plant, located in India. The bacterioplankton community differences between control (n = 16) and thermal discharge-impacted (n = 26) areas, as investigated using 16S rRNA gene tag sequencing revealed reduced richness and varied community composition at thermal discharge-impacted areas. The relative proportion of Proteobacteria was found to be higher (average ~ 15%) while, Bacteroidetes was lower (average ~ 10%) at thermal discharge-impacted areas. Intriguingly, thermal discharge-impacted areas were overrepresented by several potential pathogenic bacterial genera (e.g. Pseudomonas, Acinetobacter, Sulfitobacter, Vibrio) and other native marine genera (e.g. Marinobacter, Pseudoalteromonas, Alteromonas, Pseudidiomarina, Halomonas). Further, co-occurrence networks demonstrated that complexity and connectivity of networks were altered in warming condition. Altogether, results indicated that increasing temperature has a profound impact on marine bacterioplankton richness, community composition, and inter-species interactions. Our findings are immensely important in forecasting the consequences of future climate changes especially, ocean warming on marine microbiota.

Experimental Study on the Effect of Heat-Retaining and Diversion Facilities on Thermal Discharge from a Power Plant

In order to reduce the influence of thermal discharge from the power plant on the surrounding water environment and the operation efficiency of the power plant, a distorted physical model was presented and applied to Huadian Kemen Power Plant for studying heat transport and analyzing the effects of heat-retaining and diversion facilities near the intake/outlet on the thermal discharge for six scenarios. Field investigations were also used to validate the model. This study is unique as it is the first to elaborate on the impact of heat-retaining and diversion facilities on thermal discharge. The results indicate that the construction of heat-retaining and diversion facilities can decrease the excess temperature at intake to meet the intake requirement and improve the distribution of low temperature rise, but the area of high temperature rise has an increase. When the heat-retaining wall and diversion dike were constructed, the maximum intake temperature rise of Phase III decreased significantly by 1.0–1.3 °C with an average decrease of 0.2 °C, and the maximum value of Phase I and II was reduced by 0.3 °C with little mean change. A comparative experiment with different construction heights was also conducted. Result analysis shows that when the crest elevation was reduced from 3 to 2 m, the influence on the intake temperature rise of Phase I and II could be ignored, and the average temperature rise of Phase III only had an increase of 0.1 °C, suggesting that constructions with 2 m play an effective role in reducing heat return to the intake.