Four reactors at France’s Gravelines nuclear power plant, located along the English Channel, were temporarily shut down over the weekend after a swarm of jellyfish threatened to clog critical water intake systems.

One of the largest French nuclear power plants was temporarily shut down after a swarm of jellyfish entered the water intake systems used to cool the coastal reactors, on Monday its operator said.

Four reactors at France’s Gravelines nuclear power plant were shut down late Sunday due to a swarm of jellyfish in the cooling systems, operator EDF said on Monday, likely due to rising water temperatures because of global warming.