Salt marshes are one type
of estuarine habitat that acts like an enormous filter, removing pollutants
such as herbicides, pesticides, and heavy metals out of the water
flowing through it (USEPA, 1993). In
addition to pollutants, the same water often brings with it all of
the nutrients from the surrounding watershed. A watershed, or drainage
basin, is the entire land area that drains into a particular body
of water, like a lake, river or estuary. The nutrients flowing into
an estuarine habitat often provide for lush plant growth. For
this reason, estuaries are some of the most fertile ecosystems on
Earth. Yet, due to the pollutants they extract from waters running
through them, they may also be some of the most polluted as well.
In the animation below, as groundwaters flow into the salt marsh from the surrounding drainage area, marsh grasses and the surrounding peat extract excess pollutants and nutrients from it.