Rutgers Today:What has caused the huge phytoplankton bloom off the New Jersey coast?
Kohut: The bloom, first detected in mid-July, appears to be related to upwelling, a phenomenon that occurs often off the New Jersey coast in the summer. It’s set up by the big temperature difference between the warm surface water and the cold bottom water. When we get prolonged periods – a week or so -- of south and southwesterly winds, the surface currents move the warm surface water offshore, and the cold bottom water rises up near the coast to replace this warm water. This makes for colder water temperatures at the beach, but it also brings up a lot of nutrients. These nutrients, when combined with sunlight in the surface layer, lead to phytoplankton blooms.
Rutgers Today: Is the bloom dangerous to humans or to marine life?
These phytoplankton will turn the water green, and that makes for pretty striking satellite imagery. But if you were in a boat in the middle of the bloom, the water might not look all that different to you. And the bloom may be good news for marine organisms because it produces food and oxygen for many of the animals that live in our coastal waters. Phytoplankton blooms like this support the zooplankton and other grazers that are consumed by animals further up the food web. This could change, however, if the decay of algae rapidly depletes oxygen in the water. When algae dies and sinks to the ocean floor, it is consumed by bacteria. This process consumes oxygen in the water, and if the levels drop very low, it can stress and potentially kill some fish and shell fish. The forecast is for the winds to continue blowing from the south, at least early in the week, which will keep the bloom away from beachgoers at the shore. But that means that upwelling will continue, allowing the bloom to grow in size and thickness. We will continue to monitor the situation along with the Environmental Protection Agency and the state Department of Environmental Protection.
Rutgers Today: Is the bloom connected to climate change, or to the very warm weather we had recently?
We had a very warm July with plenty of south and southwesterly winds and not many storms, and that always helps cause upwelling. So, in that sense, yes, the bloom is related to our recent warm weather. As for the link to climate change, that’s very hard to answer. Climate change is something you can track by looking at decades of data, but it’s hard to link a particular weather or ocean event, like a phytoplankton bloom, to global climate change.
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