Physical Characteristics of Lakes
Physical Characteristics of the Lakes

Absorption of Light - different wavelengths of light are absorbed by water at different rates; this is highly dependent on what is contained in the lake water. Suspended particles and pigments within the lake water alter how light reacts with the water and ultimately affects the absorption characteristics. The depth at which 99% of all light is absorbed in lake water is known as the bottom of the photic zone. Plants require light to photosynthesize and must live within the photic zone. Therefore there is a strong relationship between the light absorbing characteristics of a lake and the aquatic life within it.

Temperature - The only part of a lake which is directly heated by the sun is the surface of the lake. How fast the temperature changes at different depths is a function of the rate of conduction and advection (stirring) of the lake water. Because water has such a high specific heat the temperature of the water changes very slowly compared to the environment around it. There are no daily changes in temperature only very slow seasonal changes. This makes lakes an ideal environment for life because organisms do not have to face sudden extreme changes in temperature.

Density - Water does not act like other matter when it comes to density; as water becomes colder, it does not necessarily become denser. In fact, density is greatest at 4 degrees celcius, this is why ice forms at the surface of lakes and not at the bottom.

Stratification - Where ever there is water above 4 degrees Celsius, you can get lakes which have stratified layers of different temperature water due to density contrasts in the water column. This only occurs when there is limited mixing of lake water due to extended periods of light winds. Warm, deep lakes with small surface areas are the most susceptible to stratification. Most lake do undergo some amount of seasonal stratification, which is a major determinant on the ecology of the lake.


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