Introduction to Benthic Introduction to Benthic

MacroinvertebratesMacroinvertebrates

Trout In The Classroom

Virginia Council of Trout Unlimited

2009 / 2010

State Water Quality StandardsState 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-Aquatic Insects as Bio-Indicators of Water Indicators of Water

QualityQuality

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 MacroinvertebratesBenthic 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

Six true legs plus lateral filamentsSix

segmented legs

More than six legs prolegs

Key ID Features -Legs

Key ID Feature – Tails

Two tails

Feather-like tails

No tail or tiny tail

Tail-like projection

Details to notice: gills

Abdominal gills

Abdominal filamentous

gillsInternal

gills

Practice ID

• Body shape?• Head? Size relative to

body?• Legs? Number?

Length? Placement?• Details? Antennae?

Eyes? Wings? Tail?Wing pads

Specimen #1

Specimen #2

Specimen #3

Specimen #4

Specimen #5

Specimen #6

Specimen #7

Specimen #8

Specimen #9

Specimen #10

Specimen #11

Specimen #12

Specimen #13

Specimen #14

Specimen #15

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 sensitiveDragonfly 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 DataInterpreting Benthic Data

Benthic macroinvertebrates can be classified according to their sensitivity and tolerance to water pollution.

Identify and TallyIdentify and Tally

Individual Species MetricIndividual Species Metric

Tolerance MetricTolerance Metric

Compute Mulitmetric IndexCompute Mulitmetric Index

Rate the StreamRate the Stream

CreditsSlides 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.