By Tom McKeon

Benthic macroinvertebrates (macros) are spineless bugs, visible to the naked eye. They are often the nymph and larvae forms of many familiar creatures buzzing and crawling around you every day. Creatures like adult dragonflies, mosquitoes, crane flies, stoneflies and many more. The presence of these critters says a lot about the quality of the network of streams they live in, including your source of drinking water.

Unlike fish, macros aren’t really mobile and tend to live within the same area of a waterway for this phase of their lives, clinging onto stones, river banks, leaf packs and anything with an inviting surface. For a macro, with its limited mobility, their habitat is at the mercy of external sources of contamination; they simply cannot swim or fly away from it.

Natural waterways are significant reservoirs of life, as ALL life depends on access to safe water – including humans. Most people in America have disconnected from that reality, as they have access to a kitchen faucet which easily provides fresh, drinkable water. It’s easy to see how someone may not think much about exactly how the water gets to that faucet, since clean water is a given to most people in developed countries.

Rivers are a common source of supplying drinking water to many cities, including Philadelphia which uses the Schuylkill and Delaware Rivers.  Our water treatment plant will filter, disinfect and remove most contaminants that we know of. However, our waterways are becoming a more and more complicated pharmaceutical and industrial waste sewers, creating a primordial soup of many unknown. It is impossible to be certain that everything harmful is removed in those treatment plants.

Yet, it is possible to inexpensively evaluate a waterway’s quality and engage public and professional awareness through biological sampling of macros. Not all macros tolerate pollution the same way and depending on the abundance, diversity, presence, as well as absence, one can get an idea of how contaminated a particular section of a stream may be.


A biological assessment won’t tell you what is causing this injustice, but it will point an observer upstream in the right direction. Perhaps there is a sewerage discharge, industrial dumping, or major runoff from a busy commercial district.

Knowing is important and engaging communities by building stream ecology awareness is essential to foster a future generation of people that understands the importance of healthy waterways and the importance of practicing caution in introducing pollutants in water.    

Conducting your own biological sampling is a fun way to engage members of the community. There are many instructional resources online, and contacting your local environmental center is the best way to learn about safe sampling methods in your community.