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Resuspension
occurs when sediment that has settled to the bottom of a bayou, lake, or
bay is redistributed through the water.
Waves created by wind or boat wakes most frequently cause this,
but sometimes it can be caused mechanically by dredging. How
does this land use cause Non-Point Source Pollution? Whether
sediment and organic matter are from natural or man made sources, they
can still cause pollution. Eventually,
both can settle to the bottom of the waterbody.
Any activity that changes the way the water flows over the water
bottom, such as wind, boats, storms, or high winds, can resuspend the
sediment and organic matter.
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Organic Matter/Low D.O:
Anytime organic matter enters a waterbody it can cause the
dissolved oxygen to drop. Resuspension of the organic matter from the bottom can act
like fresh organic matter has entered the water, causing the dissolved
oxygen to drop. ·
For
example, after Hurricane Andrew and more recently Hurricane Lili, there
were large fish kills because resuspension of large amounts of sediment
during the high winds brought massive amounts of organic material into
suspension, and used up all the oxygen in the water, so the fish
suffocated. ·
Sediment:
Sediment and organic matter in the water decrease the amount of
light that can travel through water.
When sediment is resuspended from the bottom of the water, it can
take several minutes to several days for that sediment to fall back to
the bottom and the water to clear up. This limits the distance light can travel through water,
which limits photosynthesis. It
also limits the visibility for animals that have to find food. |