1. Biological Communities in Streams
Unit 1: The Hydrosphere

2. Diversity of Organisms
Because aquatic organisms differ in their adaptations, they also differ in their habitat requirements.
Variables that affect the types of organisms in a particular body or section of water (to name a few)
Temperature
Velocity
Dissolved Oxygen (DO)
concentration
For example some fish like warm water, others like cold. Some inverts like fast moving streams, other like to bury in sediments of slower moving waters.
Mayfly Nymph

3. Food Chains and Webs
Producers – use energy from the sun to make their own food (photosynthesis)
Consumers – get energy by eating other organisms or their wastes (decomposers)
Energy (90%) is lost as you go up the food web
Decomposers – fungi and bacteria that break down dead materials (recycle nutrients)
Detritivores – same thing but larger, bug-like creatures
Food chains/webs – which is more realistic?

5. Stream Invertebrates
Producers such as algae and aquatic plants form the base of stream food webs, though bordering trees/others plants are not to be overlooked
Many inverts are scavengers – eat leaves, twigs, or other organic materials that fall in the water
Others scrape bacteria and algae off rocks
All become food for fish and other secondary+ consumers

6. Metamorphosis in Streams
Complete
Incomplete
Egg, larva, pupa, adult
Larvae shed exoskeletons to get bigger
Pupa – resting/non-feeding stage
Adults look quite different than larvae
Three stages – no pupa
Immature stage is called a nymph
Go through gradual changes to look like adult
See mayfly nymph on first slide

8. Using Inverts to Assess Stream Quality
Sensitive to environmental conditions (chemistry, physical characteristics)
DO is one of the most important – organisms need it to respire!
Adaptations for low DO:
Mosquito larvae – breathing tubes
Diving beetles – carry bubbles of air on their backs
When pollution occurs, decomposers use a lot of
oxygen which means…

9. Food Chain Activity
In a group of 4 or 5, make a specific stream food chain
On a piece of computer paper, each member of the group will draw (large) a picture of an organism in the food chain
Include the common and scientific names of your species
When your group is finished, tape your food chain somewhere around the room
Walk around to the other food chains and postulate how they might be connected (food webs)!