Tracking Tiny Critters That Have a Big Economic Punch
From the gulfs of Maine to Alaska scientists research how to predict and combat harmful algae blooms.
ABOARD THE GULF CHALLENGER, GULF OF MAINE
Lightning stabs a nearby hilltop and sends thunder rumbling through the mist lifting from the New Meadows River, just north of Portland, Maine.
It's nearly 10 a.m., and for half an hour the downpour has beaten a tattoo against the deck of our 50-foot research vessel. As the rain eases, the Gulf Challenger slows. Marine biologist Jefferson Turner and a young assistant slip a fine-mesh net over the stern.
The work under way here in the Gulf of Maine is one of two inaugural field projects this year under the ECOHAB program, a multi-agency effort to get a better handle on the ecological and oceanographic features that promote explosive growth in harmful algae and to look for ways to predict and combat the blooms.
The Gulf Challenger makes intense day-long sampling runs along a series of tracks in Casco Bay. Farther out in the gulf, larger oceanographic vessels sample waters stretching from Cape Cod to the southern tip of Nova Scotia.
Their quarry: tiny aquatic creatures that later will be tested for evidence of an algae-borne toxin that closes shellfish beds to commercial fishing, kills fish and marine mammals, and, researchers add, has been linked to illnesses in humans.
Although marine biologists have identified a few dozen types of algae that are known to produce toxins, from an economic standpoint, one of the most damaging is Alexandrium, which appears from the Gulf of Maine to the Gulf of Alaska.
Sixteen scientists from eight universities and three federal agencies in the United States and Canada lead the Gulf of Maine study, with help from Maine's Department of Marine Resources.
Their work is part of a new, five-year, $5-million research effort to gather enough information on a group of algae known as Alexandrium to allow scientists to predict when outbreaks are likely to occur and to find ways to blunt their effects.
"People tend to think of the oceanography as glamorous," muses Don Anderson, a senior scientist at the Woods Hole Oceanographic Institution, as the Gulf Challenger cuts through Casco Bay toward our first sampling site at Harpswell Sound. But, he says, it can be anything but glamorous.
Although ideally suited to the distances and intensity of the sampling runs in Casco Bay, the vessel is small enough to send much of the science team below decks in rough weather.
This past spring, the first field season for the project, was stormier than usual. In heavy seas, those fit enough to continue working had to wrestle on a pitching deck with a heavy array of eight sampling bottles as it was hoisted from the deck, lowered into the water, and returned with its load of water samples.
Instruments attached to the bottom of the array's frame return data on salinity, temperature, and depth, as well as the amount of light available for photosynthesis.
In addition to taking samples of zooplankton, which feed on algae, and water, the science team takes core samples of the sediment at the river's bottom.
Over 12 hours, we visit 16 sampling points ranging along a line from upriver to about 14 miles offshore. The run follows one of six parallel sampling tracks designed to give a picture of how currents and microscopic critters move along that section of the coast.
At two stations, Woods Hole oceanographer Jim Churchill dons a wet suit and swims to a buoy with a mesh bag filled with live mussels. He attaches the bag and returns with one previously hung there. Its occupants will later be analyzed for the presence of Alexandrium's toxins. Dr. Churchill and a graduate student also run the instruments at the base of the array of sampling bottles.
Meanwhile, the team led by Dr. Turner of the University of Massachusetts at Dartmouth continues to sift out zooplankton from its sampling net, trying to establish how Alexandrium's toxin works its way up the food chain. Later, dozens of samples packed in an ice chest will be sent to Gregory Doucette, a research oceanographer at the National Oceanic and Atmospheric Administration's National Ocean Service and the Medical University of South Carolina in Charleston, S.C., for toxicology studies. It will take several months to analyze some 800 samples sitting in his lab freezer, he says.
Such work is vital if state and federal officials are to devise measures to control outbreaks. Often, algae outbreaks are associated with man-made nutrients flushed down rivers and into coastal waters.
In the Gulf of Maine, however, pollution does not seem to trigger the blooms, Anderson says. First, he says, when outbreaks occur, "you don't get massive blooms. They are very toxic, but they're not very abundant."
Second, the blooms "do not occur in polluted areas, but in pretty clear water" associated with the outflow from the Kennebeck and Androscoggin Rivers, which empty into Casco Bay. "There's something about that river water that is special," he says.
Based on lab studies, one suspected nutrient is humic acid, a byproduct of plant decay found in "plain old dirt," he continues. When the spring thaw or heavy rains flush the rivers, they bring the nutrient along with fresh water plumes that, combined with appropriate winds and currents, can trap the plumes along the coast. Developed through years of smaller scale studies he's conducted, the "plume advective hypothesis" is holding up well as the ECOHAB group gathers more detailed data. Anderson says he's gratified.
"We have years when there's little or no algae activity," says Dr. Doucette, but this year "we have cause for optimism that we are seeing the toxic algae," based on the mussel analyses. Although it may sound perverse to wish for toxic blooms, he adds, you can't study what isn't there.
Noting that some of the results from the Gulf of Maine study could provide insights into Alexandrium blooms elsewhere, Doucette adds, "The real importance of this program is that it gives us our first chance to go into the environment and look in detail at the different aspects of algal blooms outside the lab. It will be very helpful in trying to address what's going on in other areas."