Stellwagen Bank Information

• Physical characteristics:
  • Stellwagen Bank sanctuary = 628 square nautical miles
  • Located in the Gulf of Maine.
  • 26 miles from Boston , 6 north of Provincetown, Mass 7 miles southeast of Gloucester, Mass.
  • The bank is an underwater triangular plateau 18.5 mi. X 6.25 mi. X 2.5 mi.
  • Shallowest point = 71.5 feet. Sides drop off steeply to depths > 300 feet. These sides are steep on the landward side and drop gradually on the seaward side.
• Geology:
  • Throughout history the bank has been both above and below sea level.
  • The last glaciation (75,000 years ago) pushed debris in front of it as it moved into present day Cape Cod.
  • The weight of the glacier pushed the land below sea level.
  • When the glacier retreated (18,000 years ago) it left behind the sand and gravel debris which formed the plateau.
• The bank's ecosystem:
  • "Stellwagen Bank is best described as a complex system of plants and animals whose lives are interdependent, delicately balanced, and sensitive to a myriad of constantly changing physical and chemical processes." (Ward, pg. 34)
  • Water currents and cycles move nutrients, pollutants, and marine animals about the area.
    • Nutrients:
      • East / west currents caused by tides create areas of turbulence as they move along the bottom and become uplifted by the bank.
        • Nutrients are created by the decomposition of plants and animals whose remains fall to the bottom.
        • Upwelling currents send nutrients upward from the bottom to serve as food for other marine animals.
      • Nutrients are also created on land in salt marshes, and coastal estuaries and carried outward by tides.
      • Cold water from the northern Gulf of Maine moves southward and brings along much nutrient rich water.
    • Pollutants:
      • The Gulf of Maine current collects run off from the land as it pass river mouths in Maine, New Hampshire, and Massachusetts.
        • Land pollutants can enter the ocean through this run off.
        • Most of the banks pollutants come from this run off.
      • Ocean pollutants such as oil and toxic chemicals from ships or debris from ocean dumps moves with currents form all directions.
    • Marine animals:
      • Many species of animal such as barnacles, clams, and jelly fish use the currents to disperse their young by releasing larvae to drift about to new areas of colonization.
  • Plankton
    • Plankton forms a microscopic ecosystem. Millions of plants and animals found in each gallon of sea water.
    • Phytoplankton = plant life
      • Primary producers
      • 50 species.
        • Diatoms are one species
      • Use sunlight, water borne nutrients, and clean water to begin photosynthesis.
      • The first step in all food webs.
    • Zooplankton = animal life
      • First order consumers.
      • 75 species.
        • Some are miniature animals such as copepods
        • Some are larval stages of animals such as snails, lobsters, jellyfish, cod, flounder,...
      • These animals eat phytoplankton.
  • Seasonal Change and phytoplankton
    • Summer:
      • Phytoplankton (microscopic plants) gather energy through photosynthesis from May to September. When they die and decompose, they sink to the bottom.
      • Warm surface water (up to 68 deg. F.) separates from cold bottom water (50 deg. F.) by a boundary layer called the thermocline (approximately 16 feet deep).
      • The thermocline prevents decomposed nutrients from upwelling to the surface where it could be used by other phytoplankton.
        • Upwelling currents along the bank can become strong enough to break through the thermocline.
    • Fall
      • Surface temperatures fall and the thermocline disappears allowing upwelling to occur carrying many nutrients to the surface again.
      • Photosynthesis declines throughout the fall as sunlight fades.
    • Winter
      • Very little photosynthesis occurs but great amounts of nutrients rise from the bottom.
    • Spring
      • Nutrients from the bottom combined with increasing photosynthesis (from increasing sunlight) create a "bloom" of phytoplankton. The water can turn green.
  • The marine food web
    • Phytoplankton are consumed by zooplankton.
    • Zooplankton are consumed by fish, sea birds, and filter feeders.
    • Surface waters.
      • Lots of plankton activity.
      • Marine mammals such as sea turtles, whales, are most active.
      • Sea birds prey on sand lances and herring.
    • Mid water
      • Sinking plankton consumed here.
      • Herring, squid, jellyfish float throughout this layer.
      • Humpback whales, and tuna drive schools of fish to surface to catch.
    • Benthos (Bottom) waters
      • Detritus (decaying dead marine plants and animals) collects.
      • Bottom feeders such as sculpins, lobsters, codfish, pollock, and flounder feed here.
      • Other animals include: sea anemones, sponges, clams, and scallops.