Yes, it is coincidence that these have been found right now. Please notice that the beach water at Oak Island and Caswell is not clear like Wrightsville Beach water. This turbidity is the natural result of the sediment that flows out of the Cape Fear River. And as there are many industries,the State Ports with International Shipping, etc, I think the source is much closer to home than the Gulf of Mexico.
I moved to Long Beach in 1979. You see these every so often, it wasn't something that was freakish or a cause for alarm.
Regarding the cooling system, the inlet to the cooling channel is located in the Cape Fear River. But as this cooling system is a closed loop system, essentially a big heat exchanger, like your car's radiator. The engine oil and coolant don't mix, so what flows into the channel, flows right back out.
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