The Link Between Marine Thermal Discharges and Nemopilema Nomurai Blooms Around Nuclear Power Plants

Abstract

Recent research has shown that jellyfish blooms occur more frequently near nuclear power plants (NPPs), and a relationship between thermal discharges from the NPPs and the blooms has been hypothesized. There is, however, no direct evidence that links the thermal discharges with jellyfish blooms. In this study, we conducted 3 cruises (pre-bloom, bloom, and post-bloom) during July to September 2017 in the area surrounding the largest NPP in northern China. The water temperature near the cooling water outfall rose by 2 °C. Although we found no significant impact on phytoplankton abundance or community composition near the outfall, a broader analysis of monitoring data revealed significant correlations between temperature and the abundance of Nemopilema nomurai, cyanobacteria, and haptophytes. Temperature increases may have a stimulatory effect on key stages in the life history of jellyfish, and the abundance of jellyfish prey may be the factor that triggers jellyfish blooms. Blooms of jellyfish were accompanied by a decline of diatom dominance and an increase of the concentrations of small phytoplankton such as cyanobacteria and haptophytes. This study revealed for the first time a significant positive correlation (R2 = 0.39, P < 0.001) between jellyfish abundance and concentrations of dissolved organic nutrients. This correlation suggested that the blooms of jellyfish resulted in the release of large amounts of organic nutrients. The results provided a comprehensive perspective and suggested a need for further study of the dynamics of planktonic ecosystems to link thermal discharges and jellyfish blooms.