|
|
Algae are microscopic,
one-celled or multicelled plants that live in water but
do not have stems, leaves or roots. Too much algae can
actually harm the lake ecosystem. That's because these
microscopic plants consume oxygen at night, taking it
away from fish, insects and crustaceans.
Slippery, slimy algae can also be a nuisance if you like
to swim in the lake. 
|
 |
|
|
|
Oxygen dissolved in water is
essential because aquatic
plants and animals need dissolved oxygen to live. Cold
water can hold more oxygen than warm water because gases
are more easily dissolved in cold water. Some of the
oxygen dissolved in water comes directly from the
atmosphere. Oxygen enters the water more readily when
mixing occurs, as in waves on the lake's surface. Algae
and plants that live in the water also produce oxygen
during daylight hours through photosynthesis.
|
|
|
|
|
Some fish, like trout, are
very sensitive to changes in water quality. If the lake
doesn't have enough dissolved oxygen, or if the water is
too warm, trout will die. Other fish, such as carp and
catfish, flourish in warmer temperatures and can tolerate
lower dissolved oxygen. If your lake has many trout, then
it is probably very healthy.
|
|
|
|
|
Many insects live on the
bottom of a lake and can be seen with the unaided eye.
These bottom dwellers are a food source for fish, crustaceans and other insects.
They are sensitive to dissolved oxygen levels and water
temperature patterns. Using a net, collect some
organisms from the bottom of your lake. What did you
find? Finding a variety of insect larvae, nymphs and
beetles indicates a healthy lake.
|
|
|
|
|
A lake's bottom can be
composed of rock, gravel, sand or silt. Rock and gravel
provide feeding and spawning
places for fish and insects, while sandy or silty areas
provide poor habitat and low dissolved oxygen levels.
Particles of silt and clay settle on the lake bottom,
smothering fish eggs and insects that live there. Sediment
can be suspended in the water. This makes the lake look
cloudy. Cloudy or turbid water clogs fish gills and
prevents eggs from developing properly. Healthy lakes are
clear and not noticeably green or tan in color.
|