WHOI & Bowdoin College Leverage SeaTrac for Harmful Algae Blooms

The Gulf of Maine supports productive shellfisheries that are frequently impacted by harmful algal blooms (HABs), causing annual shellfishing closures along a broad swath of the New England coast. Traditional toxin monitoring involves harvesting shellfish, testing the meat for toxins in a lab, and then shutting down fisheries when levels are too high. This approach is labor-intensive and after the fact. Scientists at WHOI and Bowdoin College collaborated with SeaTrac to deploy heavy-duty sensors that directly detect HAB species in the water, thereby improving shellfish monitoring and enabling proactive responses that better protect the coastline and its marine inhabitants.

Base Platform and Equipment 

The team relied on SeaTrac’s SP-48 USV, designed to operate in offshore waters while hosting a variety of payloads, to power the sensors and make them mobile. As the boat traveled down the sound, the sensors continued to sample and push data to a WHOI server, which classified images of individual phytoplankton cells into different taxonomic categories, identifying HABs in near real-time. Similarly, SeaTrac USV data were streamed to a shore-based server through both cellular and satellite links.

Substantial Sensors

The sensors included the Imaging Flow CytoBot (IFCB) and the Environmental Sample Processor (ESP), manufactured by McLane Labs. Relatively large and power-hungry, most testing to date has been done with these sensors moored at fixed locations or deployed from piers. Researchers placed their confidence in the SP-48 to mobilize the sensors and allow them to sample a larger body of water, thereby providing sufficiently detailed data over much larger areas.

Mutually Beneficial

The results provided information about how the instrument and the SP-48 work together, sampling in confined passages close to shore in Harpswell Sound and in the open ocean in the Gulf of Maine. It also helped determine which changes should be incorporated into SeaTrac’s production model.

The SP-48 typically runs at a cruise speed of 3 kts. With the IFCB mounted externally, the platform ran at roughly 2.75 kts. Fighting the tidal current, speed over the ground dropped another knot or more, resulting in speed over the ground of about 1.5 kts. (The SP-48 can now provide a significant increase in power with a burst speed of 4.5 kts.) 

Using the IFCB and ESP sensors in a mobile, continuous-duty model allowed researchers to detect and better predict landfall of HABs, paving the way for quicker responses and corrective measures.