do nitrates affect the health of aquatic animals?
Fish and aquatic insects can be affected indirectly
by increased nitrate concentrations in the water.
Basically, any excess nitrate in the water is a
source of fertilizer for aquatic plants and algae. In many
cases, the amount of nitrate in the water is what limits how much
plants and algae can grow. If there is an excess level of
nitrates, plants and algae will grow excessively.
Excess plants in a body of water can create many
problems. An excess in the growth of plants and algae create
an unstable amount of dissolved oxygen. During the day, there
will be usually be high levels of dissolved oxygen, and at night
the levels of oxygen can decrease dramatically.
Excess plants and algae will also create conditions
where organic matter accumulates. High densities of algae will
create a condition where sunlight cannot reach very far into the water.
Since plants and algae require some sunlight, plants and algae not
receiving sunlight will die off. These dead plant materials
will settle to the bottom of the water and bacteria that feed on decaying
organic material will greatly increase in numbers. These bacteria
will consume oxygen and, therefore, the level of dissolved oxygen
in this water will fall to levels that are too low for many aquatic
insects and fish to survive.
- This will create stressful conditions for fish.
If they are stressed for a significant part of the day, they will
not behave normally or reproduce. If the conditions persist
for a long period of time, the stressed fish species may choose
to leave that area or die off.
- Excess algae or plant growth is also unsightly.
If you've ever been to a beach where mats of rotting algae wash
up on shore or the bottom of the lake is teaming with weeds, it's
probably because excess nitrates are available for plant growth.
Several years ago, excess nitrates in Lake
Erie created such a problem; fortunately, thanks
to the efforts of concerned citizens, Lake Erie is today a much
healthier aquatic environment.
- Also, this can cause extreme changes in habitat.
Fish that need gravel or sand for spawning may find nothing but
mats of vegetation and muck.
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