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Cells may forecast next outbreak
June 8, 2005
By DOUG FRASER STAFF WRITER - Cape Cod Times
There is no good news for fishermen in the massive red tide bloom that has shut down shellfishing from Maine to Nantucket.
| An Alexandrium cell found Friday in a sample of water taken 17 miles northeast of Provincetown. (Staff photo by KEVIN MINGORA) |
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In early May, Woods Hole Oceanographic Institution scientist Deana Erdner was on board the WHOI research vessel Oceanus when the first of two northeasters blew in with high winds and big waves. The storms stirred up ocean waters, bringing nutrients from lower layers up to the red tide Alexandrium algae on the surface, feeding it like Miracle-Gro on a garden.
Suddenly, scientists on the Oceanus had a bonanza of the toxic cells to sample and analyze. Erdner, a specialist in genetics, is attempting to catalog the distinct signature of each strain of the algae. The genes combine in configurations that scientists believe may be unique to the cyst bed where each originates in the spring and fall.
Knowing the origin of the cells that help create algae blooms might help solve the puzzle of why they occur and what triggers massive ones like the current one. Genetic research on Alexandrium algae only recently became a reality after scientists figured out its gene map.
''We're really hopeful,'' Erdner said yesterday. ''We're hoping these samples are the ones that give us the answers.''
The last big red tide bloom in Massachusetts was in 1972 when Hurricane Carrie passed slowly through the Gulf of Maine, hitting a huge bloom in the Bay of Fundy. The strong winds blew the algae toward the Maine coast, where a southerly coastal current pulled the cells into waters off Maine, New Hampshire and Massachusetts.
Substitute May's two northeasters for that hurricane and you have an identical scenario this year.
The 1972 red tide bloom initiated the modern era of Alexandrium research and monitoring that has safeguarded public health for more than 30 years. Since then, there have been no fatalities reported in Massachusetts from red tide toxin. But that big bloom also seeded the ocean bottom with red tide cysts that awaken every spring, or sometimes in the fall, when water temperatures and sunlight are favorable for growth.
Explosive growth
Once they emerge, Alexandrium cells are capable of explosive growth, with each dividing into two cells every two or three days. A million cells can become 2 million in 24 hours under the right conditions.
The cells are shaped like basketballs with whiplike tails. These propel toward the surface when they hatch out of the tough cyst case that protects them through a winter or two on the ocean floor. The cysts form as the previous summer's bloom wanes, after surface nutrients have been consumed or the temperature gets too warm.
There may be a dozen or more cyst fields on the ocean bottom from Maine to Massachusetts that have been created during particularly dense blooms. Scientists worry that another may be forming in the western end of Cape Cod Bay right now.
Samples taken from some of the cyst fields last year indicate there are a lot more of them than indicated in a previous survey in 1997, said WHOI associate scientist Dennis McGillicuddy. That may be one reason that the current bloom is so large.
Another hypothesis is that conditions were favorable for growth this spring. Most of the nutrients that the algae need come from plankton.
However, the largest cyst fields are located near the mouth of Maine's largest rivers. A strong spring snow melt combined with heavy spring rains dumped more river water than usual into the ocean - fresh water that was heavy with the organic sediment that algae love.
The northeasters also fed the bloom. As plankton die off, they sink and are eaten or fall to the nutrient-rich bottom. When this layer gets stirred up by wave action, it also feeds the bloom.
Computer model
McGillicuddy, and other WHOI scientists working under senior scientist Don Anderson, are trying to build a computer model that can predict blooms based on environmental conditions.
The key question, McGillicuddy said, is how rich in nutrients the surface waters must be to trigger the bloom. The sampling done during this bloom may provide an answer.
An even deeper mystery is why the Alexandrium algae produce a toxin at all. It is a phytoplankton that uses sunlight to produce the food it needs. Some theorize it acts as a deterrent to the microscopic predators who graze on it. ''There's really no concrete ideas of why the toxin is there,'' Erdner said. But there must be a reason because ''it costs them energy to make it.''
Doug Fraser can be reached at dfraser@capecodonline.com.
(Published: June 8, 2005)