What’s Up Watershed, July Edition
Ah, summer… It’s a season full of swimming, ice cream, thunderstorms, and everyone’s favorite… BUGS! If I had to pick a favorite insect, it would probably be the dragonfly. Not only do they sport striking colors and eyes with up to 30,000 lenses, they can also help us assess the water quality in creeks, streams, and rivers.
How do dragonflies help us assess water quality? Read on to find out!
Chris Bunn
Environmental Program Coordinator
What type of insect is shown in the picture at right? Believe it or not, it’s a dragonfly! Dragonflies begin their lives in our waterways as an egg that hatches into a nymph. Nymph is another word for an immature insect, and dragonflies can spend as much as five years in this stage! After this period, they go through metamorphosis and become a beautiful adult dragonfly, only to lay their eggs in the water and start the whole process over. Check out a video of their metamorphosis here.
Dragonflies are part of a group of organisms called benthic macroinvertebrates, also known as “macros.” These are aquatic animals that have no backbone and are large enough to see without a microscope. These organisms live under and on the rocks and vegetation at the bottom of creeks, streams, and other bodies of water. Because macroinvertebrates spend most or all of their lives in the water, they are great indicators of water quality and pollution.
Some macros such as mayflies are very sensitive to pollution, whereas others such as leeches are tolerant of pollution. If a stream is polluted, pollution-sensitive macros cannot survive there. In order to know which macros are present in a particular stream, we have to go in and collect them. This is called a biological survey. By recording the diversity and number of macros in a stream, we can determine the water quality!
PRC educators take students from schools in the Philadelphia region out to streams to teach a simplified version of this process. Students collect as many macros as they can, identify them, and then compare the specimens to a chart which groups macros according to pollution sensitivity. Generally speaking, if we don’t find any pollution-sensitive macros during a survey, it’s likely that the stream has an issue with pollution. Conversely, if we find a diversity of pollution-sensitive macros, it’s likely that the water quality is excellent!
Interested in taking part in this process yourself? Check out this interactive map created by the University of Vermont to find a volunteer water quality monitoring program near you! For more information and resources on macros, visit the Stroud Water Research Center’s website. Finally, watch this short video to learn more about what is polluting our waterways.
Thanks so much for sticking around to learn about macros. See you next month at our blog for our next edition of “What’s Up, Watershed?”!
Photos shown above (top to bottom): dragonfly (courtesy of Marc Pascual); immature dragonfly (courtesy of U.S. Park Service); student identifying macroinvertebrates found in a stream; students participating in our stream stewards program
CLICK HERE to read June 2024 blog: Rain Gardens: An Upstream Solution to Pollution
CLICK HERE to read May 2024 blog: How to Plant a Nature-Friendly Landscape in 3 Easy Steps!
CLICK HERE to read April 2024 blog: April Showers: The Journey of a Spring Raindrop
CLICK HERE to learn more about watershed protection
MEET PRC ENVIRONMENTAL PROGRAM COORDINATOR CHRIS BUNN
On a day-to-day basis, Chris’ work includes creating watershed-focused educational content and supporting the implementation of nature-based solutions to residential stormwater pollution. In his free time, Chris enjoys writing and performing original music, growing food, and nerding out about native plants.
