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Research: Aquatic Macroinvertebrate Study

Dates Conducted: 1988 - present
Lead Researcher: Dr. Randy Van Dragt, Professor of Biology & Director of Ecosystem Preserve
Student Researchers: Summer Preserve Stewards/Researchers

sweep

Background

There are 13 ponds and vernal pools located in the preserve. Their study allows us to understand the composition of the macroinvertebrate community in each water body and wetland. We learn what species favor these habitats, and their population density. Inhabitants are also an indication of the health of the watershed, as finding species intolerant of pollution here would suggest preserve waters are clean.

The Study

The aquatic macroinvertebrate study is conducted every three years. A series of sweeps (dragging a D-net through 1 meter of water and weeds) is done in each pond/pool to collect macroinvertebrates. Samples are taken at various depths, from four to eight locations around the perimeter of the pond/pool. The location and depth of the sweep is recorded, and the samples are sorted and placed in jars. The macroinvertebrates are treated with Ethanol, to preserve them for identification. Using dissection scopes, books, and field guides, each sample's scientific family (and if possible, genus and species) is identified.

Findings

More than three dozen species of aquatic macroinvertebrates have been found inhabiting the study area. Some of the most common are: mosquito larvae, water boatman, backswimmers, caddisfly larvae, snails, giant water beetles, phantom midges, midge larvae, and fingernail clams. In addition, researchers have come across several interesting vertebrates, including blue spotted salamander larvae, american toad tadpoles, and green frog tadpoles.

Because of fluctuating water levels and the eventual loss of water, vernal pools are an unsuitable habitat for fish. Consequently, without predation by fish, vernal pools allow for the successful breeding of certain amphibians and invertebrates. Surprisingly though, fish have been discovered in some of these wetlands at the preserve. The fish and/or their eggs may have been spread by heavy rains connecting streams and pools, turtles wandering with eggs caught on their shell, birds carrying fish, or humans releasing fish. Upon comparing pools with and without fish, those with fish had different, fewer, and larger macroinvertebrates compared to those without fish. Three fish species currently reside in the preserve wetlands: black bullhead catfish, central mud minnows, and fathead minnows.

looking in net

What Is a Vernal Pool?

Vernal pools, also referred to as ephemeral wetlands, are depressional wetlands that temporarily hold water in the spring and early summer. They are usually found in hardwood forests after heavy rains. These wetlands slowly lose water as the summer goes on, sometimes completely drying out. They are isolated without a permanent inlet or outlet.

Importance of Vernal Pools

Vernal pools are home to obligate species (species that are completely dependent on vernal pools for parts of their life cycle). They are a safe place for reproduction of amphibian and invertebrate species, and support unique and valuable wildlife communities.

samples

Sample of macroinvertebrates

wood frog eggs

Wood frog eggs

salamander larva

Blue-spotted salamander larva

Dangers & Threats

Vernal pools, and the wildlife dependant upon them, are threatened by: mosquito control, pollution, introduction of invasive plants and animals, and habitat loss due to clearing for construction of roadways, subdivisions, agriculture, and recreation areas.

How Can You Help?

You are on your way already! Understanding the importance of vernal pools is the first step to conserving them. Learn how to identify vernal pools; many people have them in their backyards, but unknowingly destroy them. Teach others to respect its fragility. Check out these resources to learn more about protecting vernal pools:

Michigan Natural Features Inventory

Ohio Vernal Pool Partnership

Vernal Pool Association

US Environmental Protection Agency