The Bangor Daily News

Saturday, July 11, 1998

Partial lifting of red tide ban announced

By Mary Anne Clancy, Of the NEWS Staff -- MACHIAS - The Maine Department of Marine Resources lifted the first red tide warnings of the season Thursday after tests on clams in Cobscook Bay and mussels in Harpswell and Cape Elizabeth showed no danger to public health.

A red tide mussel closure remains in effect from the southern tip of Petit Manan to Schoodic Island, and Cobscook Bay remains closed to mussel harvesting as is typically the case during the summer months.The DMR permits mussel harvesting in Cobscook Bay only during the winter, according to John Hurst, the DMR's director of toxins and monitoring. In some parts of Canada, mussel harvesting has been prohibited since 1947, he said.

Red tide is weather-related and occurs from April through October, he said.Hurst said the DMR's lifting of the red tide closure for clams in Cobscook Bay coincides with the Canadian government's lifting of a red tide clam closure near St. Andrews, New Brunswick. It appears the water in eastern Maine and eastern Canada is getting cleansed of the toxic algae that cause paralytic shellfish poison, commonly referred to as PSP or red tide, he said.

The question of why red tide conditions appear to be diminishing after increasing earlier in the season is one Hurst and others are investigating. All agree water temperature plays a large role in the blooms. As fresh water, which is warmer than salt water, enters the ocean in the spring from rainfall and land runoff, it floats on top of the salt water. Algae float up and down in the water column, he said.The type of algae that causes PSP is Alexandrium tanarense. Hurst said Alexandrium reproduces by dividing. During the process, the algae develop seedlike cysts. The cysts drop to the bottom of the ocean floor and sprout. When conditions are right, the sprouts rise to the top of the water column. If there isn't enough competition from other types of algae, the Alexandrium proliferates.

Hurst is also a co-investigator in the ECO-HAB project, a federal research program on harmful algal blooms.Working with the Woods Hole Oceanographic Institute in Woods Hole, Mass., and the Island Institute in Rockland, Hurst and others are trying to determine the causes and potential solutions to the growth of harmful algae in Maine, Chesapeake Bay and Florida.Recent federal legislation sponsored by Sen. Olympia Snowe will expand the scope of that project to other coastal areas of the country by increasing funding for the program to $7 million. The Senate Committee on Commerce, Science and Transportation gave unanimous support to the legislation Thursday.

Hurst said mussels tend to be the first species to react to PSP. Mussels, which are filter feeders that survive by pumping water in and out of their systems, pump in more water than do clams. As a result, they take in more paralytic shellfish poison, Hurst said. While other states close areas to all harvesting once PSP shows up in a species, Maine approaches the problem differently, he said.''We tend to make closures on what shellfish are toxic,'' Hurst said. ''There is no reason to deny a clam digger a living because mussels are a problem.''In order to close harvesting of some species and not others, Maine conducts weekly testing throughout the summer months and into September, he said.Such testing indicated the need to close clam flats from Moose Cove at Trescott to the Canadian border on June 27. As of May 15, testing closed mussel harvesting from the New Hampshire border to Cape Elizabeth and Basin Point in Harpswell to Fort Popham in Phippsburg. Those were the warnings lifted Thursday.

Hurst said the mussel harvest closures probably don't have much of an economic impact because few people pick mussels in Cape Elizabeth and he is aware of only a few harvesters who have a small market in Harpswell. There is an economic impact to closing the Cobscook Bay clam flats for the 12-day period but it is hard to quantify, he said. As part of the ECO-HAB project, Hurst said investigators placed bags of mussels offshore in Casco Bay and have been sampling them since April. Originally there was no toxin in the mussels but then it began to build up. In the last few weeks, the toxin has gone away. The highest level of toxin was in the bag farthest offshore, an indicator that PSP's origin is out in the ocean and then moves toward shore, he said.

Philip Conkling, director of the Island Institute, said the type of algae that produces PSP is naturally occurring and has been in the ocean for thousands of years, but no one knows what causes it to proliferate at some times and not others. One hypothesis the ECO-HAB project is testing is whether ocean currents or pollution in the Gulf of Maine spread or feed the algae, Conkling said.Maine has two basic coastal currents, Conkling said. The western current begins between the Penobscot and Kennebec rivers, and water flowing from the rivers is the engine that drives this current. Many people believe pollution from these rivers - in the forms of nitrates and phosphates from sources including sewage treatment plants - provide nutrients that feed the toxic algae, he said.The eastern ocean current originates from upwellings off Grand Manan Island and the currents move to Lubec and down the coast. Here, the hypothesis is that the current brings up the many Alexandrium cysts that lie in the sediment mud, and then the currents spread the spores south along the coast to the mouth of Penobscot Bay.

Conkling said there historically have been a large number of closures on both the Canadian and U.S. sides of the St. Croix River. The St. Croix has many land-based discharges and discharges from big industries, he said.The research project is in its second year, and another hypothesis being tested is whether ballast water in ships spreads toxic algae from one part of the world to another, Hurst said. Modern ships take on and discharge ballast water in order to stabilize the vessel after loading or unloading, he said.