On the northwest side of the Passamaquoddy Bay, over 11 000 strange conical depressions cover the seabed. These “pockmarks” can be over 300 metres in diameter (that’s longer than five hockey rinks) and 50 metres deep. Scientists think that methane gas forms the pockmarks as it escapes from the seabed. Bacteria made the gas as they digested buried vegetation. Only an occasional sea star or sea cucumber is visible on the surface here. But dig down into the sediment and you will find a sub-surface city of worm tunnels, bivalve burrows, and tiny crustaceans. Discover how and why scientists study these hidden communities.
Northern Sea Star
This sea star is a predator, feeding on urchins, worms, and other sea stars, as well as bivalve molluscs like mussels and scallops. Under their legs they have small tube feet that they operate using their water vascular system—a hydraulic network of tubes and valves. Each tube foot has a valve that, when closed, creates pressure that extends it. Clams and scallops are too big to fit in their mouths—but that doesn't stop these sea stars. They use their tube feet to suction onto bivalve prey and pull their shells apart. They then eject their stomach from their mouth and into the bivalve's shell. After digesting the soft tissues of the bivalve they slurp it down.
This plump worm lives in mud and sand seabeds. They burrow head down, leaving the gills on their posterior exposed. They have a pair of large, round, ventral shields that look a bit like owl eyes and a body shaped like a resting owl. This gives them their common name “mud owl.” They feed by turning their pharynx (the top part of their digestive tract) inside out. They then use it to scoop fine particles from the seabed and feed on the organic material in these. William Stimpson described this species in 1854 from specimens found near Grand Manan in the Bay of Fundy.
This distinctive red-and-white-striped amphipod lives in burrows in muddy seabeds. Females keep eggs in a brood pouch as they develop. After hatching from the brood pouch, juveniles remain in the female's burrow for two to three months until they become more than half the size of an adult. Females feed, clean, and defend the juveniles from predators. As the juveniles increase in size, females will expand their burrow systems to accommodate their growing family. Charles Blake described this species from just over the border in Casco Bay, Maine. He named it for Dr. Robert P. Bigelow, a biologist from the Massachusetts Institute of Technology.
Explore the Seafloor
Come for a dive in Passamaquoddy Bay! Take a virtual swim along the seabed using our interactive 3D map. The seabed has been mapped using sound waves (sonar). Let images and videos introduce you to some of the amazing species that live here. Once you're back on the surface, learn about sampling methods that scientists use to collect and study seabed animals.
It is only occasionally that we find large animals on the surface of soft seabeds. But dig down into the sediment and we find thousands of animals. We call these creatures that live in the seabed infaunal benthos. Many of the species living here are so small that we need to use a microscope to identify them.
This bristle worm is also known as a scale worm, as its back is covered in soft overlapping scales. It lives in muddy seabeds in the burrows of other species. It is a predator and has two pairs of interlocking jaws that resemble a bird’s beak.Learn more
This worm has a ribbon-like body that’s capable of stretching long and thin or contracting short and thick. It is red with cream edges and can be up to 15 centimetres long. It lives in soft seabeds. It is a carnivore, often feeding on other worms.Learn more
This small cockle only grows up to 12 millimetres in diameter. It lives in the sublittoral zone, buried in gravel, mud, and sand seabeds. It filter feeds on small particles such as phytoplankton.Learn more
This clam is found in sandy seabeds. It feeds on small particles from the seabed surface. Quahogs can live for over 500 years.Learn more
Threeline Mud Snail
This snail grows up to two centimetres long. It is often found in groups on sand and mud seabeds. It is a predator that feeds on other molluscs by drilling a hole in their shell using its radula (specialized grinding teeth in its mouth).Learn more
Short Yoldia Clam
This clam prefers muddy seabeds. It feeds on particles in the sediment. It is a major component in the diet of fish such as cod and haddock.Learn more
This clam is found in soft sediments. Scientists found this species at much lower densities inside the Passamaquoddy Bay pockmarks than in the seabed around them.Learn more
This amphipod has distinctive red and white stripes. It lives in burrows in muddy seabeds. Females will expand their burrows to make room for their young. They feed, clean, and defend the juveniles from predators. The species was described from Casco Bay in Maine.Learn more
This bristle worm lives in muddy seabeds in a tube it forms from mucus and sediment grains. A member of the ocean clean-up crew, it feeds on particles of debris from the seabed surface.Learn more
Dolphin-Toothed Nut Clam
This species only reaches a size of 4 millimetres. It lives in soft seabeds. It is a deposit feeder—consuming small particles found in the sediment. Its name comes from the pointed teeth along the hinge of its shell.Learn more
This bristle worm can grow to 6.5 centimetres in length. Like other polychaete worms, it has bristles along the sides of its body. It lives in muddy seabeds and consumes particles from the mud.Learn more
This worm is found in mud and sand seabeds. It feeds on fine particles in the sediment. It burrows head down, leaving the gills on its posterior exposed. It uses oval, brown plates to protect its body at the top of its burrow. These, together with the shape of its body, resemble an owl—hence its common name.Learn more
This clam burrows up to 20 centimetres below the seabed surface. There are both recreational and commercial hand-harvesting fisheries for this species in New Brunswick. It is a filter feeder, consuming small particles such as phytoplankton. When there is a red tide event, the toxins in the phytoplankton they consume make the clams unsafe for eating.Learn more
Crystal Hiltz is a taxonomic technician in the Huntsman's Taxonomy and Biodiversity research laboratory. She uses physical characteristics to identify marine animals and plants. This work adds to our understanding of the diversity of life in our oceans, and the impact of both natural and human actions.Learn more
Not all seabed life is immediately apparent. As well as the familiar sea stars and crabs that dwell on the seabed surface, there are hundreds of thousands of tiny animals that live inside soft seabeds. We sample these by using sediment grabs to remove a chunk of the seabed, along with the animals that live in it. We then look at the grab sample under the microscope and identify the animals present. This can tell us a surprising amount about our marine environment.Learn more