and thus contributes to the overloading and
pollution of natural water systems.Biological Oxygen
Demand (BOD)
The BOD test gives an approximation of the
level of biodegradable waste in water. Examples
of waste can be vegetation, animal wastes, and
sewage. A higher BOD reading indicates a lower
dissolved oxygen content. Water with a high
BOD usually has a high bacteria count.CO 2 Aquatic vegetation, ranging from phytoplankton
to large rooted plants, depends upon carbon
dioxide and bicarbonates in the water for growth.
When the oxygen concentration falls (e.g.,
through the degradation of organic wastes), the
carbon dioxide concentration increases and the
pH increases. High CO 2 levels also make it
difficult for fish to use the limited amount of
oxygen present in the water and to discharge the
CO 2 in their bloodstream. Low CO 2 levels result
in a decreased rate of photosynthesis.
Dissolved Oxygen
(DO)
Bacteria in the water can consume oxygen as
organic matter decays and results in eutrophic
conditions, especially in the summer (the
concentration of dissolved oxygen is inversely
related to water temperature). A DO level that is
too low is often an indicator of possible water
pollution and shows a potential for further
pollution downstream because the ability of the
stream to self-cleanse will be reduced.Fecal Coliform Coliforms are a form of bacteria that are found in
the intestines of warm-blooded animals; their
presence in lakes, streams, and rivers is a sign of
untreated sewage in the water. Fecal coliforms
can get into the water from untreated human
sewage or from farms and runoff from animal
feedlots.