Biotic Indexing


The Biotic Index is a great tool for citizens to help us gather water quality data.  It’s easy to learn, fun to do, and contributes valuable data points to our public database. 


Here is how it works

The Biotic Index is a value assigned to a specific water site.  This value helps us understand how healthy a body of water is.  It is determined by collecting many macroinvertebrates, tabulating them, and using a formula provided by the New York State Dept. of Environmental Conservation.   The number and types of organisms found help to determine the condition of water quality at this site.

The Process

  • We first collect macro-invertebrates from a particular aquatic location.
  • The organisms are identified using a standard identification chart and the tabulation is recorded.

macro-intert-2There are several formulas for calculating biotic value.  Some organisms have a low biotic value, which indicates poorer water quality.  For example: If one were to find many leeches, the water quality would probably be poor. However, other insects, like Cadisfly larva, would probably indicate a higher water quality.  These organisms may serve as general biologic indicators, which reveal the environmental integrity of a body of water.

Our biotic indexing follows the guides of NYSDEC and the EPA. Here’s a link to the form we use in the field.