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Sensitivity of Freshwater Habitats Oil spills into freshwater bodies
are less publicized than spills into the ocean even though freshwater oil spills
are more frequent and often more destructive to the environment. Freshwater
bodies are highly sensitive to oil spills and are important to human health and
the environment because they are often used for drinking water and frequently
serve as nesting grounds and food sources for various freshwater organisms. All
types of freshwater organisms are susceptible to the deadly effects of spilled
oil, including mammals, aquatic birds,
fish, insects, microorganisms, and vegetation. In addition, the effects of
spilled oil on freshwater microorganisms, invertebrates, and algae tend to
spread up the food chain and eventually affect other species that depend on each
other for sustenance.
Freshwater is divided into two types: standing water (such as lakes,
marshes, and swamps) and flowing water (such as rivers and streams). The
effects of an oil spill on freshwater habitats varies according to the rate of
water flow and the habitat's specific characteristics.
Standing water such as marshes or swamps with little water movement are
likely to incur more severe impacts than flowing water because spilled oil tends
to "pool" in the water and can remain there for long periods of time.
In calm water conditions, the affected habitat may take years to restore. The
variety of life in and around lakes has different sensitivities to oil spills,
including:
- The bottoms of standing water bodies, which are often muddy, serve as homes
to may worms, other insects, and shellfish. Lake bottoms also serve has a
breeding ground and food source for these organisms and higher animals. Oil in
sediments may be very harmful because sediment traps the oil and effects the
organisms that live in or feed off the sediments.
- In the open water, oil can be toxic to the animals, frogs, reptiles, fish
and waterfowl that make the water their home. "Oiling" of plants and
grasses that are rooted or float in the water also can occur, harming both the
plants and the animals that depend on them for food and shelter. Fisheries
located in freshwater also are subject to the toxic effects of oil.
- On the surface of the water, water bugs that skim the water surface and
floating plants such as water lilies are threatened by oil slicks that spread
across the surface.
- In the shoreline habitats of lakes and other bodies of standing water,
cattails and other weeds and grasses provide many important functions for life
in and around the water. They serve as food sources, nesting grounds for many
types of animals, and shelter for small animals. Oil spills can coat these
areas, affecting the plants and the organisms that depend
on them.
- Marsh environments are among the most sensitive freshwater habitat to oil spills
due to the minimal water flow. Oil spills have a widespread impact on a host of
interconnected species. For example, lush marsh vegetation is used as nurseries
for shellfish and fish, as a food source for many organisms, and a home for
fish, birds, and mammals.
Flowing water is less impacted by oil
spills than standing water because the currents provide a natural cleaning
mechanism. Although the effects of oil spills on river habitats may be less severe or last for
a shorter amount of time than standing waters, the sensitivity of river and stream
habitats is similar to that of standing water, with a few special features:
- Oil spilled into most rivers often collects along the banks, where the oil
clings to plants and grasses. The animals that ingest these contaminated plants
may also be affected.
- Rocks found in and around flowing water serve as homes for mosses, which
are an important basic element in a freshwater habitat's food chain. Spilled
oil can cover these rocks, killing the mosses and disrupting the local ecology.
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