1. Warm up 9/20-0/21 What is the only natural lake in Texas?
Why does a thermocline form?
What is eutrophication?

2. Benthic Macroinvertebrate groups
Shredders- eat course particulate organic material Scrapers- eat algae and other substances off rocks Collectors- filter fine particulate organic material out of the water Predators- eat other living organic material Piercers- pierce open tissue of a plant or animal and inject enzyme to break down tissue

3. Benthic Macroinverts and Water Quality
Used as indicators of water quality
Separated into four groups
We count the number of species per group
Most pollution tolerant group is weighted heavily (multiply by a larger number)
Least tolerant weighted most lightly (multiply by a smaller number)
The greater the number the more polluted the river

4. Pollution tolerant organisms like clean water as well as intolerant organisms, but tolerant organisms can also survive in polluted places while those others can’t.
Example: You will find leeches and other worms (group 4) in clean water as well as polluted but stoneflies (group 1) are only found in clean water.

5. Group I: Pollution Intolerant
Need high levels of D.O.
Cannot survive in habitats affected by nutrient pollution
Mostly shredders or predators
Live in clean, cold stream. Found in riffles, why?
Canary of clean water: stonefly
Dobsonfly, alderfly and snipefly

6. Group II: Moderately Intolerant
More tolerant of nutrient enrichment and drops in D.O.
As algae increase, scrapers increase (water pennies and mayflies)
Greatest number of organisms, most diverse.

7. Group III: Fairly Tolerant
Organisms can accept low levels of D.O.
Mostly scavengers and collectors
Includes sow bugs, scuds, and right handed snail (gilled).

8. Group IV: Pollution Tolerant
Very tolerant of low D.O. and severe nutrient pollution.
Most have special adaptations for breathing oxygen at surface
left handed snail: breathes air from a pouch
Bloodworms (midge larva) have hemoglobin type blood to help them move oxygen through their body

9. Benthic Macroinverts and their groups
Caddisfly: collectors and/or shredder
Water boatman: piercer
Helgrammite (dobsonfly): predator
Water strider: predator
Dragonfly Nymph: predator
Water penny: scraper
Midge: collectors, scrapers, shredders, or predators
Mayfly nymph: scraper
Stonefly nymph: predator and/or shredder
Mayfly Nymph: collector
Blackfly larva: collectors
Damselfly nymph: predator
Tubificid worm: collector