Because a lake is a relatively static sytem, materials that enter a lake tend to accumulate in the lake. Photosynthetic organism within the lake (weeds and single celled algae suspended in the water) will use many materials as nutrients to live and reproduce. The more nutrients added to the lake the more growth the lake will sustain. Gradually the lake will take on new characteristics, becoming less clear and more shallow. This process is called eutrophication, and results from the gradual accumulation of nutrients in a lake. As the lake moves through these changes it becomes a less and less desirable place to have fun, fishing, swimming, or in anyway enjoy it. It is the events which you and the rest of your community take part in, away from the lake which affect it the most. The water which is drains from the land around the lake brings nutrients from eroded soils, fertilizers, and treated and partially treated sewage, and all of those undesirable substances are things that we use and dispose of, thinking they just disappeared.
These things drive eutrophication of your lake. Eutrophication is a natural and inevitable process, but the rate at which a lake will change is greatly amplified by our daily living. It is useful to know is the degree of eutrophication. Not only does this measure give us idea of how the lake can be used for such things as recreation and a source of drinking water, but it also gives us an idea of how the lake is functioning. An accurate and relatively easy measure of this is a series of cholorophyll samples.
Phytoplankton, one of many forms of life in a lake, are microscopic one-celled algae living everywhere in the water. Chlorophyll is the green photosynthetic pigment found in these phytoplankton, giving the lake water its green color. Phytoplankton are important not only because they are lowest on the lake’s food chain, but also because their abundance directly affect numerous water quality characteristics such as oxygen, temperature and water clarity.
When the water is filtered through paper, phytoplankton containing chlorophyll remains on the paper and can be further treated and analyzed to yield an estimate of chlorophyll concentration. In turn, this number can be used to estimate the trophic state of your lake. A lake may move through trophic states in the process of eutrophication, from oligotrophic, to mesotrophic, to eutrophic. In eutrophic lakes, there is a significant chance that uses of the lake will be impaired. A trophic state index (TSI) indicates an increasing nutrient level in the lake. Trophic is another name for production of living tissue, the prefixes oligo, meso and eutro mean few, some and many, respectively.
A series of chorphyll analyses, over time. can
give you an idea of how quickly water quality is changing in your lake.
An assessment of use of the land surrounding your lake may show you the
major sources of nutrient flow into your lake. Communication with and amongst
the local industries, home owners, government and any other organizations
can result in effective methods of slowing the nutrient flow to your lake,
keeping your lake a fun, clean and beautiful haven.
|
|
|
(m) |
(ppb) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|