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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