Water quality is graded both on appearance, for example: clear, cloudy, full of algae, and chemistry. Determining the specific levels of enzymes, bacteria, metals, and minerals found in water is extremely important. Some contaminants, such as metals and certain organic wastes, can be lethal to individual creatures and could thereby ultimately lead to extinction of certain species. This could affect both aquatic and land ecosystems and cause disruption in other biomes and ecosystems.