Scientists and State Officials Work Together to Study, Monitor Toxic Algae

Maine shellfisheries faced an unexpected challenge this fall when a toxic algae bloom caused regulators to halt harvesting along the coast. Maine's Department of Marine Resources (DMR) first closed the fishery near the Canadian border, and closures steadily spread south as the bloom intensified. Before the event was over, shellfish harvesting was put on hold as far south as Rhode Island.

These widespread closures were the result of the sudden proliferation of an algal genus known as Pseudo-nitzschia, which has long plagued West Coast fisheries but normally occurs in much lower abundance on the East Coast.

As the scope of the situation emerged, scientists quickly realized that it was a rare opportunity to investigate how and why Pseudo-nitzschia blooms occur. A team of scientists formed and successfully applied for special Rapid Response funds from NOAA to study the bloom. Scientists at Woods Hole Oceanographic Institution partnered with us to sample the waters along the Maine coast. Scientists at Florida Fish and Wildlife Conservation Commission worked with us and our current Colby College students to conduct genetic analysis of the collected samples.

"The collaboration was essential to collecting the data needed to hopefully tease out what triggered the bloom and develop methods of predicting similar events in the future," said Senior Research Scientist Steve Archer. "When you have the opportunity to study something in depth like this, you have the chance to get out ahead of it."

Algal blooms are a part of the seasonal marine cycle. Different phytoplankton species "bloom," or greatly increase in abundance, during specific times of the year and then return to a more normal state. Most of the time, this just results in a massive feast at the bottom of the food chain, but blooms of certain species can negatively impact human health.

"DMR monitors coastal waters for spikes in abundance of harmful algal bloom species," Archer said. "Once their counts reach an established threshold, DMR sends us shellfish tissue samples, and we test to see how much phytoplankton toxin is accumulating in the shellfish."

Scientists working with Archer as part of the Bigelow Analytical Services team use a technique called high-performance liquid chromatography (HPLC) to analyze shellfish samples. Bigelow Laboratory is the only facility approved by the FDA to use this method to test for the toxins that cause paralytic shellfish poisoning, and we recently received preliminary FDA approval to test for amnesic shellfish poisoning. The HPLC method provides reliable, quantitative results in less than 24 hours, which offers significant advantages over less-sensitive, non-quantitative tests on mice.

"When we tested the first samples this fall, we were surprised to see such elevated toxin levels, and the toxicity of samples just kept going up after the fisheries were closed," Archer said. "In addition to its extraordinary abundance and potency, the duration of the bloom was also remarkable. It's normal to see a brief spike or two during the fall, but this one just kept going."

There are several strains of Pseudo-nitzschia, some are harmless and others can produce domoic acid, a neurotoxin that can cause life-threatening amnesic shellfish poisoning when consumed. Even the strains that can produce the toxin don't do so all the time, and the exact conditions that cause them to become toxic aren't yet fully understood.

One condition that has induced Pseudo-nitzschia to become toxic in laboratory experiments is a rapid change in nutrient availability. Archer sees a possible connection between those experiments and two significant blooms of Pseudo-nitzschia on the East Coast – the one this summer and one near Prince Edward Island in 1987.

When there are hot, dry summers – like we had this year and PEI experienced in 1987 – they affect the ocean as well as the land. The water stratifies, separating the warmer water on top from the cooler water below and allowing very little exchange between the two. Phytoplankton, which remain near the surface, can then experience a shortage of nutrients when they use up the finite supply contained in the top layer of water. When nutrients suddenly return, through river run-off from heavy rains or wind-driven ocean mixing, the rapid change in nutrient availability can mirror the toxin-triggering conditions scientists have studied in laboratories.

"There's an environmental cue, or a combination of environmental cues, that caused Pseudo-nitzschia to become much more abundant and toxic than normal," Archer said. "Once we figure that out, we hope to develop mathematical models that enable us to predict similar blooms and alert DMR and shellfish harvesters before they occur."