Science Junction

Water What-ifs
Water Quality and Aquatic Macroinvertebrates

Macroinvertebrates Reference Desk
 * Teacher Notes, Lesson Extensions and Alternative Assessment Ideas
 * Macroinvertebrate Identification Charts
 * Comparison of Larval Stages and Adults
 * Reasons to Assess Macroinvertebrate Populations
 * Warning Signs of Pollution
 * Effects of pH Change on Aquatic Life
 * Using Lamotte water quality test kit
 * Using CBL equipment

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 effects which types of organisms can survive in a body of water. "Water quality" may include the amounts of dissolved oxygen and the levels of algal growth, pollutants which may be present and the pH level. Some macroinvertebrates such as stoneflies, mayflies and water pennies require a high level of dissolved oxygen and their abundance is an indication of good water quality.

Other macroinvertebrates can survive at a lower dissolved oxygen level because they can come to the surface to get oxygen through a breathing or "snorkel" tube or carry a bubble of air with them around their bodies or under their wings. Several species of macroinvertebrates are indicative of water systems with lower dissolved oxygen levels and include aquatic worms and leeches. Lower dissolved oxygen levels are often associated with polluted waters while higher levels indicate good quality water.



There are several reasons why macroinvertebrates are used as water quality indicators:
  • 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 collected very easily from most aquatic systems with inexpensive or homemade equipment.


The life cycle of a macroinvertebrate goes from egg to adult form and they can undergo either complete or incomplete metamorphosis. Complete metamorphosis has 4 stages, egg, larvae, pupa and adult. Organisms which undergo complete metamorphosis include true flies, beetles and caddisflies. Many of these organisms are aquatic for the egg and larval stages, but not in the adult stage. Incomplete metamorphosis has 3 stages, egg, nymph and adult. Organisms which undergo incomplete metamorphosis include stoneflies, mayflies, dragonflies and true bugs.



Many of these organisms, such as dragonflies, do not live in an aquatic ecosystem as adults. Other species such as true bugs which include the backswimmers, water scorpions and the water striders, are examples of macroinvertebrates which spend their entire lives in the water. The length of the life cycle of a macroinvertebrate can vary from less than 2 weeks for some midges and mosquitos and two years or longer for some stoneflies, dragonflies and dobsonflies.


 

Macroinvertebrate Lessons 1, 2, and 3 are intended for middle school and high school science students. These lessons focus on macroinvertebrate surveys, and how a pH change and the introduction of pesticides and fertilizers can affect an aquatic ecosystem. These lessons highlight several aspects of the following competencies:

Lesson1 Introductory Lesson-Determination of Overall Water Quality Using a Quantitative Macroinvertebrate Survey
Lesson 2 pH and Macroinvertebrate Populations-Do Changes in the pH Level Effect an Aquatic Ecosystem?
Lesson 3 Pesticides, Fertilizers and Macroinvertebrates-Does the Introduction of Pesticides and Fertilizers Alter an Aquatic Ecosystem?

Download PDF version of all three macroinvertebrate lessons.

 

 
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©1998 April J. Cleveland for Science Junction, NC State University.
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page design by Lisa Leonor Grable and April J. Cleveland
URL: http://www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/macro/index.html
Last Modified: 7/27/00

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