Stream Invertebrates, Culverts, and the Stream Environment

By the end of this Unit your students will have been introduced to some invertebrate residents of streams, and know a bit about their habitat requirements.

Unit Overview

In 2005 Tanya Blakely and fellow researchers discovered that caddisflies, a small stream insect, were slowly disappearing from local streams. The researchers found that caddisflies migrate, just above the stream surface, up streams to lay their eggs. Impeding the migration was a series of culverts on the streams. The culverts reduced the space above the stream at certain stretches of the streams and the caddisflies had no space for migration. The effects of the culverts were compounded by the presence of spiders that had spun webs in the culvert air space- consuming adult caddisflies. If the presence of culverts were having an effect on caddisflies- are they having an effect on other stream macroinvertebrates?

In this second Unit of the Culverts and Stream Ecology curriculum you will be introducing your students to stream macroinvertebrates and their habitat requirements. You will also be reviewing culverts. We do not know how culverts affect macroinvertebrates—as individual species or as whole communities—it’s an exciting line of research to be exploring. As the research project is based on students developing their own questions and hypotheses, and backing up statements with data this Unit also supports the practice of these key habits. In this Unit your students will be:

  • Developing their understanding of habitat requirements of macroinvertebrates by researching and sharing the life histories of common stream macroinvertebrates
  • Comparing stream chemistries and physical settings to make some predictions about which macroinvertebrates would be found in different locations
  • Learning about culverts as system perturbations (not all culverts are!)
  • Asking questions and supporting decisions with data

There are multiple ways to enrich the material in this Unit, many are recommended as supplements. The material within this Unit is spare, intentionally. It is the overarching goal of the Acadia Learning curricular materials that they be incorporated, interwoven, into existing curricula. You will find links to additional resources in the Unit Resources section.

We strongly encourage you to take your students on a stream habitat walk prior to your field-sampling event, as this will give them a tangible frame of reference for developing their questions. (The EPA’s Stream Habitat Walk is an excellent way for students to get their stream eyes on)


In order for your students to ask testable questions and develop hypotheses that pertain to macroinvertebrates communities above and below culverts they need a background understanding about:

  • Stream macroinvertebrates
  • Culverts as a perturbation in a system
  • Stream chemistry and physical setting

Students also need practice in developing testable questions and supporting claims with data. The formative assessment for each activity focuses on question development.


  • Students will understand that both living and non-living factors influence where and how organisms live
  • Students will know that there are communities of macroinvertebrates living in streams
  • Students will recognize that each macroinvertebrate has a different life history and has different habitat needs
  • Students will recognize how culverts, by changing stream chemistry or physical setting, might affect macroinvertebrate community
  • Students will recognize that streams have different physical and chemical characteristics (and that this may result in different macroinvertebrate assemblages)


Parts of an ecosystem do not affect each other unless one part is a predator or prey of the other part.