Pond and Lake Topics
These pages are reprinted from www.gotalgae.com, courtesy of www.kascomarine.com.
to Backyard Ponds and Lakes
ponds and lakes come in every shape and size imaginable. They can
be as little as a fraction of an acre backyard pond to a few acre
farm pond to a several hundred acre lake. These can be man made
or natural bodies of water and each can vary greatly.
a whole, most backyard ponds, farm ponds, and lakes are not managed
to prevent water quality problems. The few that are managed, usually
are managed for curing symptoms rather than preventing the actual
problem. If left alone, this can eventually contribute to the "death"
of a pond or lake.
and lakes go through a natural aging process, and considering the
"goal" of the erosion process is to fill in low areas
with eroded earth from tall areas, the progression eventually fills
in the pond or lake. Also, each pond or lake has several segments
or zones. Knowing these zones and the general aging process of your
pond or lake can help you manage your pond and slow down the aging
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and Lake Lifecycle
Typically ponds or
lakes are in either the Oligotrophic, Mesotrophic, or Eutrophic
stages of live (listed youngest to oldest).
of water are considered new or young ponds or lakes in the overall
scheme of things. Oligotrophic bodies have a low concentration of
nutrients, such as nitrogen and phosphorus. They typically have
steep sloping shorelines and are deep, clear ponds or lakes. The
bottom of the pond or lake is typically sand, gravel, or rock. Since
oligotrophic lakes have little nutrients in them, they do not produce
an abundance of aquatic plants and algae; therefore, they do not
need as much treatment for water quality problems.
of water are considered middle aged, geologically. Mesotrophic lakes
fall in the middle, between oligotrophic and eutrophic lakes. They
have more nutrients and, therefore, more plant and algae growth
than oligotrophic lakes and pond, but less than eutrophic. As a
pond or lake ages from oligotrophic to mesotrophic, the sides of
the pond begin to slope less and the bottom of the pond begins to
fill in with organic material. The substrate that was once rock,
sand, or gravel, now consists of mud on top of the rocks. Since
Mesotrophic lakes have enough nutrients to produce plants and algae,
they are in need of some treatment to slow down the aging process.
bodies of water are considered old or dying ponds or lakes. Eutrophic
lakes and ponds are extremely well nourished with nitrogen and phosphorus,
leading to an abundance of aquatic plant growth. As the pond or
lake continues to age, the sides continue to flatten out and what
were once steep sides is now gently sloping. The bottom of the pond
is now filled with organic sediment and mud. The overall depth of
the pond or lake is continually decreasing and the clarity continues
to decrease. As the pond or lake fills in and the weeds grow larger,
the total open water area shrinks as well. If left alone, the pond
or lake will eventually fill in completely, and become a swamp or
wetland at best. Most existing farm ponds fall in the eutrophic
category and need help quickly to slow the aging process.
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in the Pond and Lake Puzzle
pond or lake has several different zones that divide the water column
from top to bottom and side to side. The zones discussed are the
Littoral Zone, Limnetic Zone, Profundal Zone, Euphotic Zone, and
Littoral Zone is the shore area of the lake or pond. The littoral
zone consists of the area from the dry land sloping to the open
water and can be very narrow or very wide. Typically oligotrophic
or young ponds have narrow littoral zones due to their steep sides
and eutrophic or old ponds have wide littoral zones due to their
gently sloping shoreline and sides. The littoral zone is shallow
and gets a lot of nutrients from runoff and non point source pollution.
Therefore, it typically has an abundance of aquatic plant and algae
growth. Some other common inhabitants of the littoral zone are cattails,
reeds, crawfish, snails, insects, zooplankton, and small fish.
Limnetic Zone is generally classified as the open water area of
the lake or pond. This is a much larger section of water in oligotrophic
or younger ponds and lakes than it is in eutrophic or older bodies
of water. Within the limnetic zone are two separate sections. The
upper portion of the limnetic zone near the surface of the water
is the Euphotic Zone or Epilimnion (warm water region). This is
the portion of water that receives sunlight. The zone ends where
the sunlight fails to penetrate the water. The euphotic zone is
where algae and other aquatic plants thrive (along with the littoral
zone). Also this is the typical area of dense fish populations because
oxygen levels are typically higher due to contact with the air.
the euphotic zone is the Profundal Zone or Hypolimnion (cold water
region). More details pertaining to water temperature can be seen
on the Temperature Solutions
page. The profundal zone is located below the thermocline where
the sunlight does not penetrate. Again, the size of this zone depends
on the age and water clarity of the pond or lake. The profundal
zone typically has lower fish populations because of the lack of
oxygen during many parts of the year.
final zone is the Benthic Zone. This is the bottom of the pond or
lake and consists of organic sediments and soil. The benthic zone
is the pond or lakes digestive system. This is where bacteria decompose
organic matter from dead algae, aquatic plants, and fish waste.
More detailed information can be seen on the Aeration
and Nutrient Solutions pages.
The more organic matter in the pond, the more decomposition taking
place. Decomposition can take place either aerobically (in the presence
of oxygen) or anaerobically (without oxygen). It is much better
to have aerobic decomposition because it is a faster process and
the byproducts are easier to handle. The benthic zone increases
as the pond or lake ages.
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all may paint a bleak picture, knowing your beautiful pond or lake
is doomed. However, the overall aging process takes a long time
and there are things that can be done to slow the process. As mentioned
in the opening paragraphs, most ponds, if managed, are managed to
treat symptoms of poor water quality rather than preventing the
aquatic plants, and the gradual aging and filling in of your pond
or lake are symptoms. Most ponds that are managed are managed by
treating these symptoms. There are several options for algae control
(discussed in detail in the Algae
Solutions page) and aquatic plant control (discussed in detail
in the Aquatic Plant Solutions
page). However, just treating the symptoms repeatedly can be costly
and you are doing nothing for the actual problems.
root of the problem with the aging of a pond and water quality problems
in those ponds is an abundance of nutrients. Oligotrophic lakes
and ponds, although considered young bodies of water, can be hundreds
of years old. Conversely, eutrophic lakes and ponds, although considered
old bodies of water, can be as little as a few years. This is because
of the nutrients.
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the Aging Process is Sped Up
and human activity can greatly speed up the aging process of a pond
or lake. The nutrients come from point and non point source pollution.
Point source pollution (although may not be considered pollution
by typical standards) can be fertilizers added to the water to promote
weed growth, fish food which adds nutrients with the excess and
also speeds up metabolic process within fish to produce more waste,
and wildlife waste that is added directly to the pond. Basically,
point source pollution is anything added directly to the water.
This type of problem is usually a little easier to fix. Most of
the time, just stopping activities that add the nutrients will do
wonders (like fertilizing and feeding excessively).
point source pollution, on the other hand, is nutrients added to
the water from offsite. This can be from runoff of fertilized lawns,
cattle pastures, leaky sewers and septics, etc. These nutrients
are added to the system, but are not being added directly to the
water. Non point source pollution is typically a larger concern
than point source and more difficult to remedy. More details can
be seen in the Nutrient Solutions
page, but with runoff and other non point source pollution, the
best way to fix the problem is to keep the nutrients from entering
the pond. This can be done by adding a buffer area that will use
up the nutrients before they enter the pond, creating a diversion
of the runoff so it doesn't reach the water, or eliminate the source
altogether (ex. not fertilizing the lawn).
the excess nutrients are entering your pond, these added nutrients
are supplying aquatic plants with more than enough to grow rapidly.
The added growth will make your pond an eye sore while growing,
but when the plants die off, the greatly contribute to the aging
of your pond. As the dead plants decompose, the organic matter and
soil begin to build up in the benthic zone or bottom of the pond.
Overtime, the sludge and soil builds up and starts to fill in the
pond. An oligotrophic pond can quickly turn into a eutrophic pond
with all these added nutrients, weed growth, and organic muck on
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Pond and Lake Aging
is hope for your pond or lake, though. There are a few ways to slow
the process or even reverse it. A costly and large undertaking,
but effective process, is dredging. Dredging is physically removing
the organic matter and soil from the pond or lake. The body of water
that has filled in over the years is renewed by basically re-digging
it. By doing so the pond becomes younger and many of the nutrients
are removed. This can be a very large project, needing large machinery,
time, and money to accomplish, but you can successfully renew your
way to slow the process is physically removing the aquatic plants
before they get a chance to decompose and add to the organic matter
on the bottom of the pond. Cutting, raking, pulling, etc. are all
ways to remove the plant growth. It is essential that the weeds
are completely removed from the water and moved far enough away
that wind or rain does not wash them back into the pond. This will
be a long term project and you will put a lot of hours and effort
using this method, but over time you can successfully slow the aging
least intensive, as far as manual effort, is adding aeration and
water agitation. As discussed in great detail in the Aeration
and Nutrient Solutions page,
adding aeration is an effective tool to reducing the amount of nutrients
available for plants and keeping a pond young.
aeration device will provide your pond or lake with the oxygen it
needs. This added oxygen is not only good for the fish and other
organisms in the pond; it also helps speed up decomposition. With
oxygen, bacteria can decompose organic matter through aerobic decomposition.
This is a much faster method than anaerobic decomposition or decomposition
without oxygen. The dead organic matter that has built up in your
pond over the years will be broken down quicker with oxygen present.
This will gradually reduce the amount of sludge and muck on the
bottom through the process of bioaugmentation. Bioaugmentation is
the process of turning organic sludge on the bottom of the pond
into carbon dioxide and then venting the carbon dioxide out of the
water. The bacteria will decompose the organic sludge which produces
the carbon dioxide remains in the water, it is still available for
plant growth. However, if it is exposed at the air/water interface,
the carbon dioxide will vent off into the air. This is another great
benefit to surface aeration and agitation. A surface aerator will
splash the water, adding oxygen. It also exposes a larger surface
area of the water to the air for venting carbon dioxide and helps
get the water column mixed so carbon dioxide can vent off effectively.
aeration and water movement will also help limit algae and plant
growth in the pond to improve the overall aesthetics. The water
movement limits the amount of sunlight that penetrates the water
and limits the amount of stagnant water in the pond or lake, which
plants and algae love.
adding an aerator, like a Kasco Pond Aerator or Aerating Fountain
will help improve your ponds aesthetics by helping to limit aquatic
plant growth and help keep your pond young. The aeration will help
decompose organic sludge quicker and the agitation of the water
will help remove carbon dioxide and other nutrients. However, the
aeration will be much more effective if the amount of incoming nutrients
are limited and the existing aquatic vegetation is removed. By employing
these three tactics, you can successfully slow and reverse the aging
process of your pond or lake while improving the aesthetics, enjoyment,
and habitat for fish and wildlife.
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These pages are reprinted from www.gotalgae.com, courtesy