Nitrate is usually the most important inorganic form of nitrogen because it is an essential nutrient for the growth and reproduction of many algae and other aquatic plants. Nitrate is usually found only in waters with low dissolved oxygen levels, called suboxic waters. When an excess amount of limiting nutrient such as nitrogen is added to a lake or stream the water becomes highly productive. This may cause tremendous growth of algae and other plants. This process of enriching the water is called eutrophication. The resulting excess plant growth can cause taste and odor problems in lakes used for drinking water or can cause nuisance problems for users of the water body.
pH measures the acid content of water. The pH scale is a logarithmic scale of the hydrogen ion concentration. pH affects most chemical and biological processes in water. pH has a strong influence on what can live in the water; aquatic organisms have certain pH ranges they prefer or require. Salamanders, frogs and other amphibian life, as well as many macroinvertebrates, are particularly sensitive to extreme pH levels.
Conductivity measures the waters ability to conduct an electrical current. Pure water is a poor conductor. Salts increase the conductivity of water.
Turbidity refers to water clarity. Turbidity means that the water isn't clear and there's stuff in it. If water is turbid that means it's not clean and there are sediments suspended in the water. Turbidity decreases with the presence of molecules and particles that can absorb or scatter light. Dark or black material absorb most wavelengths of light. The size of a particle is important as well. Small particles can scatter light. The fate of light entering a water body depends on the amount, composition and size of the dissolved and suspended material.
Dissolved oxygen is a product of photosynthesis and diffusion. The warmer the water, the less oxygen it can hold. Most organisms need at least 5 or 6 ppm of oxygen. Even cold water rarely contains more than 15 ppm. Summer is often a time of oxygen stress for aquatic organisms. Cold water can dissolve more oxygen than warm water. For example, at 25 degrees Celsius, dissolved oxygen solubility is 8.3 mg/L. Whereas at 4 degrees Celsius the solubility is 13.1 mg/L. As temperature goes up, water releases some of its oxygen into the air.
Temperature influences the amount and diversity of aquatic life. Lakes that are cold and have little plant life in winter, bloom in spring and summer when water temperatures rise and the nutrient rich bottom waters mix with the upper waters.Because of this mixing and the warmer water temperatures, the spring overturn is followed by a period of rapid growth of microscopic aquatic plants and animals.
Alkalinity refers to the waters ability to neutralize acids. Its produced by minerals like limestone. Water with low Alkalinity is acidic.
Escherichia coli are coliform bacteria found in the intestines of warm-blooded organisms. Most strains are harmless, but do indicate the presence of other harmful pathogens. These can cause diarrhea and kidney damage.
