Subject: Estuary = Dynamic System

Phillip Colla (
Wed, 09 Jun 1999 10:04:22 -0700

Why is an estuary called a 'dynamic system' ?

Although this is not directly related to cetaceans or marine mammals,
I'll take a stab at it.  I believe "dynamic" is used to describe
estuaries because estuaries are ever-changing, principally due to
tidal effects.  Consider:

  Sometimes shallow water or mud flats, sometimes deeper water.
  Water flowing in from the ocean, water stationary at high or
     low tide, water flowing out to the ocean.
  Water flowing in from contributing fresh water sources, such
     as streams or rivers.
  Changing salinity, water clarity, water temperature.
  Sometimes an estuary may be cut off from its water sources, so
     that is become a "standing" body of water.  This in itself
     causes changes that estuary inhabitants must deal with, such
     as diminishing oxygen levels in the water, changes in water
     temperature, inability to flush out pollutants, etc.

The animals that inhabit an estuary must deal with all of these
stresses, and probably many more that I did not mention.  The changing
nature of the estuary environment is dynamic.

Best regards,

Phillip Colla
Research Associate: