What is an aquatic macroinvertebrate, anyway?

dragonfly pic
Photo by Katie Burandt

As you probably know, “aquatic” means water and “macro” means big—at least big enough for you to see without a microscope. “Invertebrate” means without a backbone. 

Macroinvertebrates are excellent indicators of water quality. They also play a key role in nutrient cycling. Studies suggest they are responsible for processing a whopping 73% of riparian leaf and litter in streams. They also serve as food for fish, amphibians, reptiles, birds and mammals.

A simpler term for a macroinvertebrate is either macro, or water bug. Some of the most well-known macros are dragonflies and caddisflies.

Water bugs thrive in different types of aquatic habitat, like swift running streams, wider, slower rivers or shallow ponds. Some live in the soft sediments of deeper lakes and ponds.  While many eat leaves and twigs, others feast on algae or insects.

Numerous macros live their entire lives in water. Others hatch or spend their youth in water, then live on land as adults.  For many macros, their adulthood lasts a very limited time. Take the mayfly, for example. Their fleeting adult life lasts as little as 24-48 hours.  

Some of the most popular macros are dragonflies. These water bugs are aquatic or semi-aquatic as juveniles for up to six years. As adults, they leave the water to forage for insects, their primary food choice, often several miles from water. That is why you see dragonflies along cliff bands and in forests and pastures.  

Dragonflies are exceptional migrants—with the longest nonstop multi-generational migration of 11,000 miles—across oceans. Yes, the small but mighty globe skimmer dragonfly (Pantala flavescens) is not deterred from crossing large bodies of water. By utilizing favorable tailwinds, and with lumps and bumps on its corrugated wings that counteract turbulence and facilitate lift, this remarkable macro is hypothesized to migrate from India across the Indian Ocean to East Africa each fall, with the next generation returning to India the following spring. 

You can read more about this fantastic journey here.