Resource Highlights

The Sanctuary encompasses within its boundaries each of the four major seafloor habitat types - piled boulder, gravel, sand and mud - found in the Gulf of Maine. These habitats are spread across the series of banks and deep basins that make the Sanctuary the diverse topographic area that it is. This unique seafloor topography combines with tidal currents, seasonal mixing and annual circulation patterns to support a diverse array of species, from microscopic phytoplankton to large marine mammals.

Plankton - Life in the Water Column

The highest concentration of phytoplankton, and resulting peak in primary productivity, in the Sanctuary occurs from December through early April. During this period, more than 675 species of phytoplankton have been documented. Although there are common species occurring throughout the year, this spring bloom is characterized by both a higher number of species and higher overall abundance. A second, less-marked period of heightened productivity also occurs in mid to late summer, during July and August.

In contrast, the number of species of zooplankton (or secondary producers) in the Sanctuary remain relatively constant throughout the year. Though zooplankton do not experience seasonal fluctuations of the same magnitude as phytoplankton species, there is a distinct seasonal pattern to their abundance. Zooplankton production begins along coastal waters of Massachusetts north of Cape Ann during March. Production continues to expand throughout the southern Gulf of Maine and the Sanctuary throughout April, peaking by the end of May. The vast majority of the zooplankton species occurring in the Sanctuary is endemic to the Gulf of Maine.

Benthic Invertebrates - Life on the Seafloor

Every major taxonomic group of invertebrates that occurs in the global marine environment occurs in the Sanctuary specifically. Benthic invertebrates occur throughout the Sanctuary across all seafloor habitat types and constitute the major component of biological diversity. While large cerianthid anemones may be the most visible in a deep mud basin, sand dollars and sea stars might dominate the shallower sand areas. Structure-forming epifaunal invertebrates (such as sponges and anemones) provide critical nursery habitat for juvenile fish of many species (such as Atlantic cod and Acadian redfish), while the greater invertebrate community provides an important source of food for these and many other fish species in the Sanctuary.

A Diversity of Fishes

Fish are a vital component of the Sanctuary's biological diversity, and are also one of its strongest links to the human population. The diverse seafloor topography in the Sanctuary supports a wide array of fishes. For instance, of the 176 fish species captured in more than two decades of government trawl surveys throughout the Gulf of Maine, 66 of those species have been sampled in the Sanctuary. Fish found in the Sanctuary range in size from small snake blennies to basking sharks, the largest of the fish occurring in the Sanctuary. Some fish, such as giant blue fin tuna, are annual migrants to the area, while others, such as Acadian redfish, are likely year-round residents.

The groundfish community in the Sanctuary, made up of fishes such as cod, haddock, whiting (silver hake), and various flatfish, has been sought for food from the earliest European settlements to the present. And the sand lance, whose populations are seasonally prolific in the Stellwagen Bank environment, serves as the primary prey of Humpback whales feeding within the Sanctuary.

Sea Turtles Among Us

The Sanctuary is the seasonal home to two species of endangered sea turtles, the Atlantic or Kemp's ridley and the leatherback. The leatherback is a regular summer visitor and is the only species of sea turtle that journeys to cold waters for feeding activities. Likely prey include jellyfish and other jelly organisms abundant in these waters during the summer. Atlantic ridleys are observed in waters off Massachusetts as juveniles, having either swum or drifted north in the Gulf Stream from hatching areas off the southern coast of Mexico. Southern New England waters are important feeding grounds for ridleys.

Whales on the Horizon

Large cetaceans are the most visible occupants of Sanctuary waters. Seventeen species are known to frequent the Sanctuary, and rare sightings of two additional species have been recorded. Because of their large size, flamboyant behavior, and distinctive markings, Humpback whales (Megaptera novaeangliae) are perhaps the most observed and easily identified of the Sanctuary's cetaceans. Feeding assemblages of over 40 animals are common during the Spring, Summer and Fall. The species was first scientifically described based on observations made of an individual taken off the coast of Maine, and hence, the Latin name novaeangliae, which means "New England."

Northern right whales are the most seriously depleted species of large cetaceans. Given its endangered status, the photo-identification of at least 100 northern right whales using the Sanctuary and adjacent waters seasonally indicates the particular importance of this system to a significant portion (about one third) of the existing total North Atlantic population for feeding and nursing activities. Fin (or Finback) whales, the second largest of the World's whales, are the most common species of large baleen whale in the Gulf of Maine and are regularly seen in the Sanctuary, along with the smaller Minke whales.

The most frequently observed toothed-cetacean is the white-sided dolphin, with single groups sometimes numbering over 1,000 individuals. Pilot whales and harbor porpoise are also frequent. Orca (or killer) whales are occasionally observed on Stellwagen Bank, where they are thought to follow schools of bluefin tuna from mid-July to September.

The Presence of Pinnipeds

Two pinniped species are known to occur in Sanctuary waters, the harbor seal and the gray seal, though neither are common. Harbor seals, the more common of the two species in the Sanctuary, range from Labrador to Long Island, New York, and is the most abundant pinniped species in eastern United States waters. Gray seals are the most abundant pinniped species occurring in southern areas of eastern Canada, from Labrador south through the Bay of Fundy.

An Abundance of Seabirds

Over 40 species of marine birds are found throughout the year in the vicinity of the Sanctuary. The distribution and abundance of seabird species in the Sanctuary are related, as they are in other parts of the Gulf of Maine, to the availability of preferred prey (such as fish and fish larvae, cephalopods, crustaceans and offal). With a single exception (Leach's storm petrel), all seabirds occurring within the Sanctuary are either migrants or non-breeding residents. The high levels of biological productivity in the Sanctuary, combined with the presence of fishing vessels, result in a predictable and abundant variety of associated species of both coastal and pelagic seabirds.

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Revised January 13, 2006 by Stellwagen Bank National Marine Sanctuary Web Group
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