Tuesday, June 07, 2005

Alexandrium the Great: Is the Red Tide on its Way to the Sound?

Alexandrium fundyense, a toxic species of alga that is responsible for so-called red tides, has been spreading throughout coastal waters, from Massachusetts through Maine, over the past couple of weeks. Shellfish feed on the algae, and if you happen to eat a quart of steamers in which the toxins have accumulated, it could well be your last meal.

News accounts, as well as information from the Woods Hole Oceanographic Institute, indicate that this year's red tide is more widespread than at any time since 1972. Generally it does not affect Cape Cod, and a toxic red tide in Buzzard's Bay is all but unheard of. And yet there it is, forcing health and environmental officials to shut down shellfish beds throughout the region. If you're heading to Nantucket or the Cape any time soon, the shellfish you eat won't be local.

The outbreak, and its spread into waters where it's usually not found in great numbers, has made me wonder why Alexandrium fundyense has not bloomed in Long Island Sound. The answer seems to be that Alexandrium isn’t found in the Sound in great numbers to begin with and the winds and currents haven’t pushed it here from the east.

Here's what Oceanus, Woods Hole’s magazine, reports:

In most years, natural current and wind patterns keep the cells from flowing into the coastal waters of southern New England. But during a spring marked by unusual amounts of rain and snowmelt and steady stream of northerly and easterly winds—capped by nor’easters on May 7-8 and May 24—ocean conditions developed almost perfectly for a massive bloom.

Anderson and McGillicuddy [two WHOI scientists] offered several possible explanations for the widespread algae bloom. The first is that the unusual weather patterns this spring—particularly the wind-driven currents from the north—pushed an abundance of Alexandrium cells south into Massachusetts Bay and Cape Cod Bay. Another idea is that there was a larger source of cells in the Gulf of Maine, following an intense bloom off western Maine in autumn 2004. Or perhaps the record-setting precipitation of this winter and spring flushed more fresh water and nutrients into the coastal region, creating better conditions for the cells to grow and reproduce. Finally, ocean conditions this year may have favored a particular strain, or genotype, of Alexandrium in the western Gulf of Maine.

So it seems that this strain of Alexandrium is usually confined to waters north and east. Darcy Lonsdale, an ecologist at Stony Brook's Marine Sciences Research Center, told me in an e-mail:

Apparently there are some cells of Alexandrium in Long Island waters but to my knowledge this alga has not bloomed here. Why I really can't say, except that this particular alga has a history of only blooming in waters north of here.

For it to move south and west, it needs unusual conditions to push it in that direction: Unusual winds and currents, nutrients to act as fertilizer, lots of rainwater and snowmelt to wash the nutrients into the sea.

Phil Colarusso, a marine biologist with EPA:

This is primarily circulation driven. The stuff has just made it down around Cape Cod, so any sustained wind out of the east would drive it into Narragansett Bay and Long Island Sound. Fortunately for them, the winds tend to come out of the southwest this time of the year.

But his colleague, Eric Nelson, says:

It's moving in that general direction. With many beds in Nantucket and Buzzards Bay now closed, towns in RI, CT, and NY might be getting nervous. How far it gets will probably depend on longshore currents, wind direction and speed, water temperatures, and sunlight.

New York officials don’t seem especially worried but they are on the lookout. Newsday reports today that the waters around Fishers Island will be tested for Alexandrium.

If it happens, it’s clearly a no-win situation. Alexandrium seems to affect steamers and mussels, even when they’re cooked, more than quahogs and oysters, but all shellfish beds will be closed (not that many shellfish beds aren’t already closed permanently or occasionally because of sewage). Finfish and lobsters aren’t affected (not that there are many lobsters left).

If you should happen to make the mistake of eating a pot of infected mussels, you’re in big trouble. Here’s what happened to a half dozen fishermen working George’s Bank in 1990:

After a hard day of fishing, the fishermen settled down in the ship's galley to eat a pot of steamed mussels that they had incidentally caught in their nets. The Captain, who had joined the meal later than the rest of the crew, witnessed his fellow fishermen become incapacitated due to the paralytic effects of the toxin. He himself also became ill, but was capable of sending an urgent radio message to the US Coast Guard. The Coast Guard airlifted the men to the nearest hospital located on Nantucket Island, MA where they were treated using respiratory therapy to sustain their breathing and prevent them from dying due to paralysis of the lungs.

Late night update: About a half hour after I posted this, I got an e-mail from Professor Sandra Shumway of UConn's Department of Marine Sciences, at Avery Point. Here's what she said:

The red tide hasn't affected Long Island Sound quite simply because it
hasn't reached the Sound. Same with Rhode Island waters. These areas have been blissfully unaffected by red-tides and this latest bloom is huge. It's not a matter of environmental conditions, right now it's a matter of a unique set of circumstances -- meteorological andoceanographic -- that have driven the red-tide laden waters around Cape Cod and through the CC Canal. Check out a map that is regularly updated at: http://www.mass.gov/dfwele/dmf/programsandprojects/psp_notice.htm#shelsani

(Thanks to Mel Cote, Kathy Rhodes, Susan Maresco, and Sherrill Baldwin for helping put me in touch with the experts on this.)


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