Biodiversity

Insect Collection and Biodiversity

For much of its existence the areas around the Cahaba River remained mostly undeveloped. The growing number of people moving into areas around the Cahaba, especially in Shelby and Jefferson Counties, has lead to increased problems with water quality. Although both point sources and non point sources of pollution are of concern, non point is harder to detect and control because it comes from sources that are not easily identifiable. During this portion of the trip teachers will seine for fish and collect benthic invertebrates and correlate the relative abundance of specific organisms present with the quality of the water.

Fish Fish can be used as indicators of the relative health of a river. If a river contains high populations of fish that are very tolerant to pollution then the body of water probably contains more pollutants. If a section of the river has high numbers of pollution intolerant fish, then the river is more likely to be clean and have higher amounts of dissolved oxygen. The table to the right shows the number of species found in the Cahaba River basin.
Fish species are classified as intolerant, intermediate or tolerant to pollution. Fish species intolerant to pollution speckled chub weed shiner mimic shiner highfin carpsucker black redhorse blackbanded darter harlequin darter longear sunfish	blackbanded darter longear sunfish
Fish species of intermediate tolerance to pollution American eel Alabama shad silverjaw minnow silver chub stripped shiner golden redhorse mosquitofish bluegill largemouth bass river darter	bluegill mosquitofish
Fish species tolerant to pollution green sunfish largescale stone roller pretty shiner	largescale stone roller pretty shiner
Benthic invertebrates Although fish can be used as biotic indicators, benthic invertebrates are most commonly used. Benthic invertebrates are small vertebrate-less organisms that live on the bottom of a river or stream for at least part of their lives. Benthic invertebrates have short life cycles which means that a change in population can easily be monitored if a pollution event has occurred. The three most pollution sensitive insects are mayflies, stoneflies and caddisflies.
Pollution intolerant invertebrates Stoneflies Dobsonflies Water Penny beetle mayflies alderflies mussels	stonefly mayfly
Invertebrates mildly tolerant to pollution damselfly dragonfly crayfish isopod	dragonfly crayfish
Invertebrates tolerant to pollution midgeflies worms leeches pouch snails	leech pouch snail

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