|MadSci Network: Environment/Ecology|
Dave, This question is much too broad to answer in this format. I urge you to seek information in your local library or go to the library at a nearby university, agricultural experiment station, or EPA office. Sounds like a cop-out doesn't it? Well here is why. The term "pollution" can cover a variety of physical and chemical changes made to the natural system, in this case water. How they affect plants depends on the nature of the pollutant. Here are a few examples. Nitrate fertilizer is a pollutant in many areas. Nitrate can be toxic to humans especially young children and infants. They are far from toxic to plants, however, and are basically a fertilizer, resulting in increased growth of emergent plants and algae. This can be a boon to plant eating organisms in the water body or can result in noxious algal blooms and perhaps low oxygen levels when the bloom dies out. Another example is heavy metal pollution. There is evidence that heavy metals can be toxic to some plants and algae, but many fish appear resistant to heavy metals. Some fish concentrate metals in their tissues making them toxic to us, though. And how about turbidity? Turbidity, or the amount of particulate material in water makes water unpleasant to look at, especially in drinking water settings. No-one wants to drink cloudy or brown water, even if that water contains no harmful constituents. That turbidity, however, lowers the amount of light that reaches submerged plants and algae, decreasing their photosynthetic capacity. I could go on and on. There are many books written on this subject with more examples, and more pollutants. Happy hunting!
Try the links in the MadSci Library for more information on Environment/Ecology.