Introduction to Benthic Macroinvertebrates Trout In The Classroom Virginia Council of Trout Unlimited 2009 / 2010
State Water Quality Standards • Standards are based on how we use water: • 1. • 2. • 3. • Standards include a general requirement that all state waters are free of pollutants harmful to animal, plant, and aquatic life. This standard allows the state to consider stream habitat and aquatic insects as indicators of water quality.
Aquatic Insects as Bio-Indicators of Water Quality • There are important reasons why benthic macroinvertebrates are used to assess water quality: • 1) they are found in all streams; • 2) there are many different species; • 3) they stay in the same spot in a stream; • 4) they react to different conditions in the stream over long periods of time; and • 5) they are easy to sample and identify.
Benthic Macroinvertebrates • Benthic = dwelling on stream bottom • Macro = large enough to see with naked eye • Invertebrates = without a backbone • Other benthic aquatic organisms = aquatic insects that have three body parts (head, thorax, abdominal segment) and six legs When you try to identify an organism, these are some details to notice
Key ID Features -Legs Six true legs plus lateral filaments Six segmented legs More than six legs prolegs
Key ID Feature – Tails Tail-like projection Feather-like tails No tail or tiny tail Two tails
Details to notice: gills Abdominal filamentous gills Abdominal gills Internal gills
Practice ID • Body shape? • Head? Size relative to body? • Legs? Number? Length? Placement? • Details? Antennae? Eyes? Wings? Tail? Wing pads
Benthic Macroinvertebrates can be classified according to their sensitivity to pollutants.
Sensitive Mayfly larvae Stone Fly larvae Most caddisfly larvae Beetles (adults and larvae)
Somewhat sensitive Dragonfly and damselfly larvae Netspinner caddisfly larvae Crayfish Gilled snails Aquatic sowbugs Scuds Clams and mussels True fly larvae Hellgrammites, Fishfly and Alderfly larvae
Tolerant Lunged snails Black fly larvae Midge larvae Aquatic worms Flatworms Leeches
Interpreting Benthic Data Benthic macroinvertebrates can be classified according to their sensitivity and tolerance to water pollution.
Credits • Slides and notes used in this presentation were provided for educational purposes by: • Virginia Save Our Streams • Virginia Department of Conservation and Recreation • Alice Furguson Foundation – Bridging the Watershed • Audubon Naturalist Society • And a very special thanks to Darrell Schwalm of the Shenandoah Valley TU chapter for putting this presentation together.