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The Questions
Why does my lake/pond smell unpleasant and look stagnant ?
Many lakes/ponds tend to stratify,
that is they separate into distinct layers.
Though lakes vary in many dimensions they are actually highly structured, similar to a forest ecosystem where, for example a variety of physical variables (light,temperature, moisture) vary from the soil up through the canopy. It is useful to visualize a more extreme example of stratification: Imagine a bottle salad dressing containing vegetable oil and vinegar. The oil is lighter (more buoyant) than the vinegar which is mostly water. When you shake it up you are supplying the energy to overcome the buoyant force, so the two fluids can be uniformly mixed together. However, if allowed to stand undisturbed, the more buoyant(less dense) oil will float to the top and a two-layer system will develop. In lakes and ponds this prevents atmospheric oxygen from reaching the lower water areas. Lakes that circulate poorly result in water that remains stagnant. Why does my pond/lake have so much algae?
Algae provides food for fish. Algae occurs naturally in all types of systems and may be considered
indicators of a healthy ecosystem condition.
However, some can become so dense they can ultimately cause a problem with low oxygen levels. A decrease in oxygen causes hypoxia (low oxygen) or anoxia (no oxygen) and the other organisms in the water that need oxygen to survive, such as fish, become stressed and die. Other blooms may release toxins that can be harmful to animals.
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