Biological Indicators of Healthy Waters

Healthy rivers and streams tend to indicate a healthy lake. There are many indicators that can describe the health of the water, some more accessible than others.  Taking samples to a lab to test for parameters such as dissolved oxygen, pH, conductivity and nutrients is often the standard procedure.  Using biological indicators, such as benthic macroinvertebrates, allows us to have a visual and tangible clue to the general ecosystem health and environment which they are living.

There are many functions that benthic macroinvertebrates (BMI) contribute to water systems, such as enhancing biodiversity, playing critical role in the food web and acting as a strong indication of stream health and dynamics.  The most common BMI are grouped separately by their tolerance towards pollution, ranging from intolerant, tolerant to insensitive.  Ephemeroptera (mayflies), Plecoptera (stoneflies), and Tricoptera (caddisflies), also known as EPT taxa, are BMI under the intolerant group.  When the EPT taxa are highly abundant in an ecosystem, it indicates that their habitat has low levels of pollution, meaning that even intolerant species are able thrive in that setting.  You would find that as water quality improves, there would be an increase in the abundance of EPT taxa.

(Guest author – Kelsey Colbert, VT Lakes and Ponds Program)

EPT taxa you might see when you look closely. Images from the UNH Center for Freshwater Biology http://cfb.unh.edu/StreamKey/html/index.htm l