Study On Sources And Trajectories Of Giant Jellyfish In Coastal Waters Nearby Hongyanhe Power Plant

The structure and function of marine ecosystems have experienced significant changes due to climate changes and human activities.Following the green tide and red tide,jellyfish as a colloidal zooplankton has attracted more and more attention for its explosive population.Jellyfish bloom would lead amounts of jellyfish entering the cooling system water intakes of power plants and clogging them,imposing a potential threat to the safe operation of the coastal power plants.At present,jellyfish has become a typically disaster-causing organism at the water intake of coastal nuclear power plants.To solve this problem,it is fundamental to determine the sources and trajectories of jellyfish and explore the process of jellyfish aggregation.Taking Hongyanhe Power Plant as a case,this study constructs a backward particle-tracking model based on particle-tracking method and coupled with a hydrodynamic model,to trace the sources and trajectories of giant jellyfish in waters nearby Hongyanhe Power Plant and analyze the seasonal changes and interannual differences of jellyfish sources and trajectories.To determine the jellyfish sources more realistically,physiological characteristics of jellyfish are also considered.This would be of instructive significance for preventing and controlling of jellyfish disasters in coastal waters.The results indicate that:(1)the jellyfish nearby the power plant come from different sources,including the western and northern parts of the Liaodong Bay and the north and south sides of the power plant;(2)affected by water temperature and circulation,the main sources and trajectories of jellyfish migration during June to September are different.The jellyfish that appeared in June is likely generated locally,while the high-risk jellyfish disasters in July to September mainly result from the physical aggregation of jellyfish from different sources in the Bohai Sea;(3)there is a significant interannual differences in the sources and trajectories of jellyfish nearby Hongyanhe Power Plant.The jellyfish that appeared in the power plant waters in July2013 mainly came from the coastal waters in the north of Bohai Bay,while mainly from the western coastal area of Liaodong Bay in 2014;(4)Both wind field and river runoff influence the circulation pattern in the Bohai Sea,and then affect the sources and trajectories of jellyfish nearby Hongyanhe Power Plant.The wind field is an important factor affecting the circulation and jellyfish trajectories,and the impact of the Liaohe runoff on the cyclonic circulation in the Liaodong Bay is weak;(5)According to main trajectories of jellyfish,it is suggested that a closed monitoring section should be conducted in the area about 15 km from the power plant intake for real-time jellyfish monitoring.Another section can be set up in the area about 30 km away from the intake,in which a fixed-point trawl survey was conducted every 5 days from the early July to mid-August.In the southwest direction 15-20 km from the power plants,intercepting and cleaning up jellyfish.Besides,the wind field can be used as an important indicator of monitoring and predicting,which can provide reference for the seasonal prediction of jellyfish gathered in waters nearby power plant.