Tuesday Morning: Stepping Stones for Red Tide, and New England's Jump on Coal Burning

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two models show how red tide might move
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Two circulation models show that wind direction during an Alexandrium bloom can be crucial. Red colors indicate higher concentrations of Alexandrium. Left: after northeasterly winds, cells concentrate in Massachusetts Bay, as happened in 2005. Right: southwesterly winds sweep cells out into the open ocean. (Courtesy Don Anderson, WHOI)

Organic pollutants fall from air into freshwater
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When wood burns, carbon-14 values in organic pollutants like PAH are much higher than when fossil fuels like coal or oil burn. The compounds get into lakes and bays mainly by falling from the atmosphere. (Jayne Doucette, WHOI)

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2005: Northeaster Sweeps Red Tide into Massachusetts Bay
A perfectly timed northeaster made a bad situation worse, pushing already high concentrations of Alexandrium up against the New England coast. The red zigzag line shows the sampling course of the research vessel.
Courtesy Don Anderson, WHOI
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Related Links

» Harmful Algae and Red Tides
A WHOI Coastal Ocean Institute topic page, with links to articles and Web sites.

» Red Tide - Gone for Now, But Back Next Year?
More about the prognosis for another Alexandrium bloom next year. From Oceanus magazine.

» Seeing Red in New England Waters
WHOI researchers detect a massive bloom of algae before it hits the coast. From Oceanus magazine.

Prospects look mixed for a New England red tide in 2006

Although last summer ended with hurricanes battering the Gulf Coast, New Englanders remember it starting with the most severe outbreak of harmful algae—often called red tide—on record for the area. With summer 2006 approaching, people are wondering whether last year’s bonanza has set the seeds for another record bloom.

On Monday morning, Don Anderson gave a talk that revisited the 2005 bloom and outlined why it was so bad. Citing new survey results, he cautiously suggested that southern New England may not have to go without local clam chowder for another summer.

The culprit, Alexandrium fundyense, is a microscopic sea plant that makes tiny amounts of toxin. When concentrated by filter feeders such as clams, the toxin can paralyze or kill humans. Each fall as the growing season ends, Alexandrium cells turn into cysts that drop to the sea floor and lie dormant, like seeds, until the next year.

In Anderson’s view, three crucial events coincided last year to create the epic bloom: unheard-of numbers of cysts, a skim of freshwater runoff for the cysts to float in, and a bitter northeast storm to blow the water - and the cysts -into the cul-de-sac of Massachusetts Bay.

Anderson, a WHOI senior scientist, led a team that surveyed the sea floor in Massachusetts Bay and south of Cape Cod for dormant Alexandrium cysts last November. He took his first look at the data a few days before the meeting.

The good news: cyst numbers are about half what they were in 2004, the winter before the bloom. The bad news: that’s still two to three times higher than in normal years.

Anderson calculates that there may be as many cysts in New England waters as in 2004, but spread over a wider area. The big worry is that cysts from southern areas may form a stepping stone for a bloom to develop south of Cape Cod again and perhaps drift even farther west.

Or, Anderson said, the weather in May and June may deliver different winds that sweep cells out into the open ocean and away from shellfish beds.

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Century-old pollutants finger their source

It took a trip to the middle of Lake Superior to find out, but it appears New Englanders may have been burning fossil fuels well before the official beginning of the Industrial Revolution. That’s what Ana Lima suggested yesterday after presenting results collected from the mud of Isle Royale, Mich., and Rhode Island.

Lima, an MIT/WHOI Joint Program graduate who works at ExxonMobil, examined organic pollutants made up of carbon rings (called polycyclic aromatic hydrocarbons, or PAHs) that had built up on the floor of a lake and a rivermouth. Lima studied them because their molecular makeup allows her to track the kinds of fuel that people burned in the past.

The technique works because fossil fuels are much, much older than firewood. So when researchers carbon-date their samples, the values they get for wood vs. fossil-fuel PAHs are nowhere near each other. The difference is so great, in fact, that scientists can look at intermediate carbon-date values for a particular place and estimate the ratio of fossil fuels to wood that was being burned there.

PAHs are also useful because it’s very rare for them to be produced by any process other than burning, so their carbon scores can’t be muddled by factors other than the fuel type.

Lima and her co-authors, Chris Reddy and Tim Eglinton of the WHOI Marine Chemistry and Geochemistry Department, sampled a Rhode Island rivermouth and found PAHs with a 70% fossil-fuel signature as early as about 1850, several decades before the Industrial Revolution began in earnest.

The values indicated much more fossil fuel burning than during the same period at a remote location—a lake on an island in the middle of Lake Superior. But the signatures still suggested about 20 percent of the PAH came from fossil fuels. Results like these may be of use in determining how far industrial smoke can travel on the winds before settling out.

Lima, who is Brazilian, said she had hoped to analyze lakes in the Amazon Basin, as a means of augmenting the sparse records of energy consumption in her country. But her samples produced very small amounts of PAH. Despite the large amount of burning in Brazil, not much of the residue seems to fall back on Brazilian soil, perhaps because they get carried off by the strong trade winds.


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Last updated February 23, 2006
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