Three Bays Preservation - Cape Cod, Massachusetts
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June 2006 Sea Lettuce in North Bay

Gross sea lettuce infestations are a major problem in many parts of the world and the use of mechanical harvesters to remove it has been successful. Sea lettuce thrives when soluble nitrogen, almost always from sewage, mixes with phosphorus rich seawater.
In the open ocean, dilution prevents excessive growths. However, in poorly flushed estuaries, accumulating concentrations of nitrogen
along with the phosphorus naturally present in seawater, cause extensive growths of sea lettuce and other undesirable algae.
In the Three Bays, the source of nitrogen is groundwater which contains the nitrogen rich effluent from onsite septic systems.
Due to the porous soil on Cape Cod, septic systems have been successfully and widely employed for sewage treatment. Unfortunately,
the nitrogen impacts of these systems was largely ignored until estuaries on the South Shore of the Cape lost almost all of the
eelgrass that is so essential to a thriving estuary.

Timeline:

  • Prior to 2002 there were little or no sea lettuce deposits in North Bay
  • Each year, the problem has been worse than the prior year
  • It is anticipated that the growths will continue move southward throughout our estuary system.

Management:

  • Options for managing the problem include hiring a contractor to harvest the sea lettuce or independantly purchasing harvesting equipment, which is cost prohibitive.


Pictures of North Bay from June 2006



Sea Lettuce

Sea Lettuce2

Sea Lettuce

Sea Lettuce

 
 
     
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