Woods Hole's Top Expert Explains the Red Tide (Yet Another Sphere Exclusive)

Don Anderson is the scientist at Woods Hole who has been leading the research on the red tide and the Alexandrium algae. His opinion then is probably the best we're going to get on what's been happening this year. Here's what he told me in an e-mail about how it spreads and whether it will reach Long Island Sound:

In northern New England, there are huge "seedbeds" of Alexandrium cysts that serve as an inoculum for blooms when those cysts germinate. The currents then carry the germinated cells to the south, during which time the cells divide and accumulate, causing the red tides. Those currents and their associated cells are diffused and dispersed as they head south. By the time that water has rounded Provincetown on Cape Cod, the cells are usually not that abundant because of mixing, dispersal, and nutrient limitation. This year, they were quite abundant for reasons we don't fully understand yet, so we had toxicity quite far "downstream" at Nantucket and Martha's Vineyard. I expect some cells will have traveled even further and gotten to Long Island Sound this year, but I doubt enough will make it that far to be of any concern.

I thank him for responding.