Temperature - Aquatic organisms may be found over a wide range of temperatures from hot springs where some bacteria exist in water that is close to the boiling point to water that is always ice covered. Different organisms are adapted to particular ranges of temperature. Increasing temperature by addition of hot water to natural systems may cause native species to be eliminated. Warm water contains less oxygen and the increased temperature will increase the metabolic activities of many of the organisms in this water. It is more able to withstand inputs of acid without the pH dropping.
Many organisms seem to be restricted to water within some range of hardness.
Many invertebrate, for example, require calcium for their shells or exoskeletons. Chloride - Chloride occurs naturally in low concentrations in natural water. It will tend to be higher in precipitation in areas near the ocean. Increased chloride levels may come from domestic sewage, food processing or other activity, and road salt. Nitrate and Phosphate - These two nutrients are important for the growth of algae and other organisms.