The pH readings are temperature dependent. Specific instructions for the model carried on-board are posted next to the instrument. Before it is used, the aquatic science instructors calibrate the pH meter. Changes of pH can be associated with wastewater discharges and sources of pollution. However, natural changes in pH occur with variations in levels of carbon dioxide.
Carbon dioxide is very soluble in water.
It enters the water from the atmosphere and is also generated from animal and plant respiration and decomposition. Dissolved carbon dioxide can combine with water to yield carbonic acid. Plants, however reduce amounts of carbon dioxide through photosynthesis making surface waters more basic. Water quality standards generally call for a pH of between 6.0 to 9.0. A pH between 6.7 and 8.6 will support a well-balanced fish population.