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Transcript
Using Invertebrates as
Environmental Indicators
Devils River West Texas
What is a watershed?
• A watershed is a geographic area in
which water, sediments and dissolved
materials drain into a common outlet.
• Watersheds are affected by all of the
activities that take place within its
boundaries.
San Antonio River Watershed
Pollution
• Pollution is the introduction of a contaminant into the
environment
• Can you name some types of water pollutants?
• Fertilizers, bacteria, silt, chemicals
• What about sources of pollution?
• Sources can include wastewater treatment plants,
parking lots, construction sites, factories, agricultural
areas, urban areas.
Types of Pollution
• Point Source Pollution--Point source refers
to a specific discharge location such as a
wastewater treatment plant or discharge
from a factory
Types of Pollution
Non-Point Source Pollution--Non-point source
pollution is a pollutant that does not have a
single point of origin, for example the parking
lot from the school
How do we know if a stream is
polluted?
We could conduct a test!
Biological Testing
• Scientist use macroinvertebrates as one
tool to assess the overall health of a
stream
• Macroinvertebrates-- Small animals
without backbones that live in the stream
• These insects are usually the larval or
nymph stage of terrestrial insects such as
mayflies and dragonflies. Benthic(bottom)
insects are used for biological testing
Why
- Abundant
- Small
- Sensitive to the
Environment
- Short generation
times
- Easy to collect
- Not very mobile
?
Biological Testing
Use Benthic Macroinvertebrates as indicators
Advantages:
Inexpensive, gives information
about past & present water quality
Disadvantages:
Time, identification can be difficult
Macroinvertebrates
Aquatic macroinvertebrates feed in many different ways,
some are predators, while others are filter feeders or plant
consumers
https://www.youtube.com/watch?v
=RD5wsoycsqI
Stream Habitats
• Pools—areas of slow moving water
generally containing lower concentrations
of dissolved oxygen
• Riffles—areas of faster moving water with
generally higher concentrations of
dissolved oxygen
Pools
Riffles
Procedure
1) Collect a sample from a body of water:
a) D-nets
b) around riffles (where water
flows around rocks)
c) under rocks and plant
debris( pool areas)
100 organisms would be a good
sample size to represent
community diversity
A D-Net Being Used For Collection
Types of Pollution Sensitivity
• Sensitive or intolerant---These types of
Macroinverts are very intolerant of poor
water conditions.
• Somewhat sensitive or intermediate—can
live in moderately degraded conditions
• Tolerant—can live in most conditions in a
stream unless severely polluted
Very Sensitive
•
•
•
•
•
•
Mayflies
Stoneflies
Dobsonflies
Caddisflies
Riffle Beetles
Water Pennies
Somewhat Sensitive
•
•
•
•
•
Crayfish
Damselflies
Dragonflies
Diving Beetles
Water Scavenger
Beetle
• Right-handed snail
•
•
•
•
Tolerant
Black Flies
Midge Larvae
Mosquitoes
Left-handed/
pouch Snails
Why are some sensitive?
• Insects breathe in different ways- some breathe
through their skin, some with gills, and some use
the air from the surface.
• Which do you think are most tolerant of
pollution?
The beetle, can move long distances and breathes
surface O2
Practice Your Identification
Skills!
Open the following link and practice
identifying some of the common benthic
macroinvertebrates:
- Identifying Benthic Macroinvertebrates
Activity