Key for Classifying Aquatic Invertebrates

Introduction: Key for Classifying Aquatic Invertebrates

Aquatic environments are filled with life, from tiny microscopic organisms that can be seen with the unaided eye, to insects that cling to rocks and burrow into silt. Aquatic invertebrates that can be see without a microscope include aquatic stages of insects like the dragonfly nymphs as well as clams and worms. They often go unnoticed because of their size and habitat, but are an extremely important part of the aquatic ecosystems. Collecting and identifying aquatic invertebrates can provide insights water conditions. We have developed a key that helps young people identify and count aquatic organism samples and use this sample as an indicator of water quality.

Step 1: A Key Young People Can Use

Many of the existing keys provide written identifiers that leads observers to an identification of an invertebrate. These keys are often associated with flipping pages to eventually arrive at the order an invertebrate belongs to. These keys don’t work for many young people. Our key is different. It provides a chart with both images and descriptors that quickly help the individual identify the organism.

Step 2: Dichotomous Keys

Dichotomous keys provide a choice using observable features. Our key uses a branching chart with each branch containing a simple descriptor. The key uses two sides of 11x17 charts. The first descriptor decides which side of the chart is to be used: legs or no legs.

Step 3: Key With Images on a Page

A water sample containing invertebrates is emptied into a tray and an individual specimen is picked up and put in a smaller examination container. Each order is identified with information, diagrams and illustrations. Drawings, rather than photos, have been used to aid in identifying the order of the invertebrate that is being examined. Drawings tend to focus and simplify significant features minimizing many of the distracting features included in photos.

Step 4: Additional Information Beside the Images

The descriptions provide classification information, scale, feeding, common name and detailed descriptive information. This information is bundled together with the image so that all the information can be checked to confirm an identification.

Step 5: Use of the Chart to Determine Water Quality

Different orders of invertebrates are able to survive in different types of water quality. Some orders can tolerate high levels of pollution but others must have good water quality to survive. This key provides groupings related to water quality. By keeping track of both the different orders and the population of an order in the sample, we are able to gather an overall water quality index. The Key is used in conjunction with a spreadsheet that automatically calculates this index when the numbers of the orders are entered. If the sample is divided into a number of trays so that a number of people can take part in the analysis. The following website provides access to both the key and the related spreadsheet.

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