Waterford — Waterford High School teacher Mike O'Connor brought one group of students, or a cohort, to the salt marshes in Alewife Cove on Tuesday to explore.

As part of O'Connor's marine biology class, he pointed out features, such as the top layer of microbial mat, or multiple layers of microorganisms, that includes the purple sulfur bacteria that turns the sand of the salt panne, or marsh pool, pink and purple.

The class has two cohorts that attend school in person and one that attends classes online at home. Two cohorts will be taking trips to explore a salt marsh and tidal flats while the third group will watch prerecorded Facebook videos that O'Connor made at those locations. Later on, all three groups will take a trip on the Project Oceanology boat to visit an estuary.