Glossary
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1. Acidity
The term acidity refers to the capacity of water to resist a rise in pH, i.e., a decrease in H+ concentration, when it is mixed with bases. Acidity is measured by adding sodium hydroxide, NaOH, to a known volume of water until the pH increases to 8.0. The more NaOH required to raise the pH to 8.0, the greater the acidity of the water. Examples of sources of acidity in streams and lakes are acid mine drainage and acid rain. Related terms: pH, Alkalinity
2. Algae
Algae are one-celled plants that live in lakes and oceans. They live near the surface, where sunlight can penetrate. Algae are the foundation of food webs in aquatic ecosystems: They are eaten by microscopic animals called zooplankton, which are eaten by fish, which are eaten by larger fish, mammals, and birds. The growth of algae is limited by the availability of phosphporus and nitrogen nutrients. In freshwater lakes like the Finger Lakes, the limiting nutrient for algae growth is generally phosphorus. Related terms: Chlorophyll, nutrients, trophic status, Secchi depth
3. Alkalinity
The term alkalinity refers to the capacity of water to resist a drop in pH, i.e., an increase in H+ concentration, when it is mixed with acids. Alkalinity is measured by adding sulfuric acid, H2SO4, to a known volume of water until the pH decreases to 4.3. The more H2SO4 required to lower the pH to 4.3, the greater the alkalinity of the water. An example of a source of alkalinity in streams and lakes are underground limestone formations. Related terms: pH, Acidity
4. Ammonia
Ammonia, NH3, is the major form of nitrogen present in animal and human waste. Ammonia is toxic to aquatic life. One of the principal functions of sewage treatment plants is to remove ammonia from wastewater before it is discharged to streams and lakes. Related terms: Nitrogen, Total Kjeldahl nitrogen, total nitrogen
5. Bacteria
One-celled organisms that are found virtually everywhere in nature, including water, soil and air as well as inside animals and plants. Bacteria are a class of microbes. Other microbes include viruses, fungi and parasites. The vast majority of microbes are harmless to humans, and some are beneficial. However, some microbes are capable of causing serious and even fatal diseases. Microbial diseases were much more common a hundred years ago than they are today. The birth of microbiology as a science in the 1870s and the improvements in sanitation that followed, for example, the purification of public drinking water and the construction of sewage treatment plants, are the main reason for the decrease in water-borne diseases such as cholera, typhoid and yellow fever. Vaccines and antimicrobial drugs have also played an important role in controlling microbial diseases. Indeed, when it comes to water, the main threats to human health are generally due to microbes. From a public health standpoint, the risk of chemical contamination is relatively small compared to the risk of microbial contamination, although when chemical contamination does ocur, for example, near a Superfund toxic waste site, it can constitute a serious publich health threat. The risk of microbial contamination is commonly assessed by testing for members of one large family of bacteria, the coliforms. Tests are generally not conducted for each of the many possible disease-causing microbes themselves, because that would take too much time and money. It would be like looking for the proverbial needle in a haystack. The microbes that are tested for, coliform bacteria, are not harmful (with the exception of a few rare strains). However, as concentrations of coliform bacteria rise, there is an increasing probability that disease-causing bacteria are also present in water. In other words, coliform bacteria are used as a risk indicator, a red flag for the potential presence of water-borne microbes that are capable of causing disease. Related terms: Total coliform, E. coli, fecal coliform