Biological Communities in Streams Unit 1: The Hydrosphere

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

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?

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

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

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…

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)!