Coastal Salt Ponds

Coastal Salt Ponds

Coastal Salt Ponds (.jpg - 61k)

A coastal salt pond is a shallow marine embayment that receives freshwater inflow from groundwater entering the head of the pond, and saltwater inflow through an inlet from the sea. The inlet is periodically opened and closed by the shifting of barrier sands.

Tidal and groundwater inflows mix to form a salinity gradient in the pond. Much of the pond's plant and animal life is segregated along this gradient, because different organisms prefer different salinities. However, conditions will vary greatly with the opening and closing of the inlet, and some organisms will not survive the sudden changes in salinity.

When the inlet is closed for a long period of time there will be large-scale die offs among the plant and animal communities, and massive decay will give off unpleasant odors and make the pond unsightly. When the pond is reopened by a breach in the barrier beach the organisms adapted to the fresher water conditions will then die off due to the increasing salinity levels.

Dredged Inlet   

The recently dredged inlet of a coastal salt pond. The inlet was almost completely blocked off by a coastal storm, but dredging has insured a vigorous tidal exchange.( 59k - jpg)

  

On Cape Cod, salt ponds are only found in Falmouth, and many of these are no longer true salt ponds because they are kept permanently open to the sea by dredging or the use of jetties. Rare natural habitats are being lost because nearby residents do not want the ponds undergoing the natural cycles of decay.

Due to limited tidal flushing, salt ponds are very prone to degradation by pollution from a variety of sources, such as improper septic systems and road runoff. Dredging and filling may physically destroy communities, or it may increase the tidal flow, thereby affecting plants and shellfish.