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The information below is meant to help clarify some of the important terms used in water quality monitoring. New content may be added in the future.


Nutrients are the elements, or chemical compounds, that are essential for life. Some are very common like carbon, oxygen and hydrogen …. others are less common like calcium, chlorine, potassium, sodium, iron, sulfur, phosphorous and nitrogen … and some, while relatively rare, are molecules certain organisms need but can’t produce (vitamins) or metals like zinc, manganese, copper and selenium.  There are certain nutrients that are often limited in the natural world setting and therefore control population growth rates …. these include the elements phosphorous and nitrogen. These two elements are the focus of new nutrient regulations that affect some of us directly in our work. Here are some references that will help interested people understand more about nutrients and how we measure their quantity (and therefore impact) in the environment:

General nutrient information:




More Technical:


Water Monitoring:



Bacteria are microscopic, single cell organisms. People interested in water quality use bacterial (and sometimes viral or parasite) concentrations to assess the potential of fecal contamination by animals (including humans). An observed higher concentration than normal in environmental waters could indicate a potential health concern. One bacteria species that is frequently used as an indicator is Escherichia coli (E. coli). It is a very minor component in the human (and typically other animals) gut, but for historical reasons is easy to analyze and enumerate. It is naturally observed (along with other bacteria) in relatively low concentrations in streams frequented by wildlife (and domesticated animals). A few strains of bacteria can cause serious infections and disease, but sophisticated analyses are required to differentiate them from the great majority that are harmless or beneficial. Recent biological studies of bacteria have demonstrated that they vastly outnumber cells in the human body (10:1), are beneficial (if not essential) to life processes, are unique in population diversity to individuals, vary in population diversity from one part of the body to another, can transmit genetic information (eg immunity) from species to species without sexual reproduction and live in genetically diverse populations that enhance survival. We are only beginning to understand bacteria as essential to all higher life forms.


Metals are elements and, although they do not degrade, they have complex environmental chemistry. Metals occur naturally in the environment and some are essential for living organisms. The effects of metals on human and aquatic health can be far reaching. Metals can be toxic to aquatic plants and animals in certain concentrations and can bioaccumulate* in some species, such as mussels. Lead, which is often used as an indicator for other toxic pollutants in stormwater, can be harmful or deadly for human and aquatic life. Zinc, although not harmful to humans at concentrations normally found in stormwater, can be deadly for aquatic life. Cadmium can bioaccumulate* in an ecosystem, soil microorganisms are especially sensitive to it, and it is harmful to human health. Some metals bind to soils and organic matter and are transported in sediment, while other metals dissolve in water. Some accumulate in the sediments of streams, lakes, and estuaries as well as in fish tissue. Certain heavy metals are nutritionally essential for a healthy life, but large amounts of any of them may cause acute or chronic toxicity (poisoning). Trace elements such as iron, copper, manganese, and zinc are commonly found naturally in foods we consume or as part of a vitamin supplement. Trace metals, such as arsenic, copper, cyanide, mercury, nickel, and lead can also even come from air emissions from far away factories. Heavy metals are also part of the manufacturing process of many common household items, such as pesticides, batteries, electroplated metal parts, textile dyes and steel, to name a few. These metals may also come from industrial waste discharges, solid waste landfill leachate, agricultural waste, transportation equipment or corroding metal pipes and storage tanks. If interested, the below references are helpful for a more in-depth understanding of metals and how we measure their quantity (and therefore impact) in aquatic environments:

General Links on Elements

* Bioaccumulation – “Progressive increase in the amount of a substance (metals for example) in an organism or part of an organism which occurs because the rate of intake exceeds the organism’s ability to remove the substance from the body.”