Scientists from the National Centers for Coastal Ocean Science (NCCOS) recently completed the annual Gulf of Maine cyst sampling cruise aboard the NOAA Ship Gordon Gunter (February 17 – March 2, 2026). The research cruise is conducted annually to measure Alexandrium catenella cyst abundance in seafloor sediment samples, which helps inform the red tide forecast for the Gulf of Maine.
Alexandrium is a dinoflagellate species that alternates between a planktonic, swimming phase and a resting benthic (sediment) cyst phase. Alexandrium survives the cold winter months by forming dormant, seed-like cysts each fall that overwinter on the seafloor. When water temperatures warm in the spring, the cysts germinate into free swimming algae that repopulate the water column. These motile cells can grow in excess, causing harmful algal blooms.
Blooms of Alexandrium can produce potent neurotoxins that can accumulate in marine shellfish, and consumption of shellfish contaminated with these toxins can cause a serious, and potentially fatal, illness called paralytic shellfish poisoning (PSP). PSP poses a serious risk to commercial and non-commercial shellfish harvesting and aquaculture in the Gulf of Maine region, so the forecast products are provided to the states of Massachusetts, New Hampshire and Maine as well as an array of other regional stakeholders to help guide PSP monitoring and mitigation efforts.
The scientists collected sediment samples using a Craib corer along an array of 70 stations throughout the Gulf of Maine. Once a core is collected from the bottom of the Gulf, the team cut the top centimeter from each core and processed the mud to isolate the cysts into sample tubes. The cysts collected in each sample will be counted under a microscope at the NCCOS Beaufort Laboratory in North Carolina. Samples will also be used to investigate molecular methods that may replace visual counting of cysts and speed up the cyst quantification process.
These data will be used to produce a map of the distribution and abundance of cysts across the Gulf of Maine. Cyst distribution data are combined with meteorological data from the National Weather Service to forecast severity of the spring Alexandrium bloom. In addition to the seasonal forecast, weekly forecasts will be produced and available online throughout the spring and summer months.
This work is authorized under the Harmful Algal Bloom and Hypoxia Research and Control Act (33 U.S.C. §§ 4001 et seq.).
