The Role of Macroinvertebrates

May 8, 2013

Within everyone’s place, there is an all-important aquatic system. You can begin your own local ecosystem expedition by identifying your river or stream, and then by asking — and discovering — what lies beneath the surface. Understanding the role of these water resources and the life that teems around and within them is vital, and gathering facts about your aquatic study place is the key to knowing if the system is healthy and growing.Understanding and becoming aware of the life in an aquatic source enables you and your students to become explorers and stewards of your waterway. The presence or absence of specific organisms is a direct indicator of the health of an aquatic system. Such is the role of the macroinvertebrate.

Start by learning about the leading indicator of the overall health of an aquatic system — the presence of macroinvertebrates. Just beneath the surface lies a world of underwater creatures that rely on a healthy water system to survive and thrive. Observing these populations in a water system can impact the health and future of the source.


Aquatic macroinvertebrates are found in lakes, streams, ponds, marshes and puddles and help maintain the health of the water ecosystem by eating bacteria and dead, decaying plants and animals. Overall water quality affects which types of organisms can survive in a body of water.Water quality may include the amounts of dissolved oxygen, algal growth levels, and pollutants which may be present and, thus, affect the pH level. Some macroinvertebrates, such as stoneflies, mayflies, and water pennies, require a high level of dissolved oxygen. Their abundance within a sample is an indication of good water quality.

Other macroinvertebrates, such as aquatic worms and leeches, are suited to survive at lower dissolved oxygen levels by their ability to surface for oxygen, or by carrying an air supply around their bodies. These macroinvertebrates are indicative of lower dissolved oxygen levels, and are often associated with poor quality or polluted waters. Macroinvertebrates are excellent water quality indicators for several reasons:

  • ‍They are sensitive to changes in the ecosystem.
  • ‍Many live in an aquatic ecosystem for over a year.
  • ‍They cannot easily escape changes in the water quality.
  • ‍They can be easily collected from most habitats using inexpensive or homemade equipment.

The life cycle of macroinvertebrates goes from egg to adult form, and they can undergo either complete or incomplete metamorphosis.

Complete Metamorphosis
‍Complete metamorphosis has four stages: egg, larvae, pupa, and adult. True flies, beetles, Caddis flies, and the Water Penny each undergo complete metamorphosis. Many of these organisms are aquatic during the egg and larval stages, but not in the adult stage.
Incomplete Metamorphosis
Incomplete metamorphosis has three stages: egg, nymph and adult. Organisms which undergo incomplete metamorphosis include Stone flies, May flies, Dragon flies and true bugs.

Many macroinvertebrates, such as Dragon flies, begin life occupying aquatic habitats in the egg and larval stages, becoming terrestrial in the adult stage. Conversely, species like the backswimmers, water scorpions, and water striders spend their entire lives in the water.The life cycle of macroinvertebrates can vary from under two weeks for some Midges and Mosquitos, and up to two years or longer for some Stone flies, Dragon flies, and Dobson flies.To understand the role of macroinvertebrates in the aquatic and land ecosystems, one must be aware of their presence and activity in local aquatic systems. Performing a population study is the beginning to such an awareness, and is reflected as an awareness and activity of environmental stewardship.

Stephanie Miller

With over 25 years experience, Stephanie serves as a senior copywriter, social media director, and senior editor for Science Scene. Stephanie is always on the lookout for new educational and STEM-related opportunities and technology.