|MadSci Network: General Biology|
Water can become turbid, or cloudy, for many different reasons. Fine sediments, such as silt, are easily disturbed and can hang suspended in the water for amazingly long periods of time. A gentle current can be enough to keep these sediments suspended indefinitely. Sometimes, water can be naturally dyed. Here in Florida, we have many trees whose leaves contain tannin, the same chemical that makes tea brown. And Tea Brown is the exact color of most Florida lakes and streams. This can contribute to apparent turbidity. By far the most common, and probably the most ecologically significant cause of turbidity, however, is organic growth. Algae and other microorganisms can grow in the water, sometimes at tremendous rates. This is one reason why turbidity is used as a test of water purity. An interesting note is that water which is very pure often indicates a sick lake, since extremely low turbidity generallly indicates that something is killing off the aquatic organisms that cause the water to be cloudy. Obviously pollution is a factor that can lead to turbid waters. The pollution itself can cloud the waters, it can kill native shoreline vegetation that usually filters out run-off - which leads to siltification, and it can increase microbial growth by increasing the nutrients many kinds of algae need. I hope this helps, and good luck on your experiment! Your mad scientist, S. Kohler
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