Fund Pollutants. Fund pollutants are those for which the environment has some assimilative capacity. If the absorptive capacity is high enough relative to the rate of discharge, they may not accumulate at all. One type of fund water pollutant is called degradable because it degrades, or breaks into its component parts, within the water. Degradable wastes are normally organic residuals that are attacked and broken down by bacteria in the stream. The process by which organic wastes are broken down into component parts consumes oxygen. The amount of oxygen consumed depends upon the magnitude of the waste load. All of the higher life-forms in watercourses are aerobic; they require oxygen for survival. As a stream’s oxygen levels fall, fish mortality increases, with the less tolerant fish becoming the first to succumb. The oxygen level can become low enough that even the aerobic bacteria die. When this happens, the stream becomes anaerobic and the ecology changes drastically
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