Water Habitats,
Water Habitats,Summary: In this activity, students use their discoveries from their field trip to consider the variety of habitats in water.
Preparation: You might have an outline of water habitats drawn on the board before class.
Material:
Card set of water "citizens"
Large sheet of paper attached to wall, or board for lake profile drawing.
ACTIVITY STEPS:
Ask students to think back over their water exploration. What questions do they have? Would they like to follow up on anything in particular? If the whole class were to pick one question, what would it be? (If you can encourage debate, discussion and research on a topic of their own interest, so much the better.)
Ask students to consider:
Where are possible habitats in a body of water?
They may mention that life in water can be found on or at:
Water surfaces, both on top and on the underside of the surface
Swiming or floating at different depths
Bottom (slower water has more sand, silt and clay), including the on and under rocks
Soil of banks
Surfaces of suspended material
On OTHER plants and animals in waterThey might also mention that life has adapted to certain conditions, including:
light
temperature
saltiness (salinity)
presence or absence of certain food and predators
Consult a big map of these areas on the board, and ask:
Who might live in the water habitats you have observed??
Have students brainstorm the question. Have them draw representative cards for their ideas.
Next pass out the pre-made cards that include some creatures they might not have thought of.
Ask students to tell you or class artists where to place each "critter" on the appropriate section of the water profile. Explain that this is the profile of a lake, but other types of water have other profiles. Ask how an ocean profile would be different (deeper, some different animals and plants, continental shelves, trenches etc.)Once the organisms are in place, ask your students to consider:
What changes could upset these habitats?
Changes in any of their list of adaptive factors (salnity, temperature, light etc.) might make a habitat unsuitable.
Toxins like oil and gas, nitrates and dry cleaning solvents are among compounds found in water run-off. These all harm life in the water. Some of the run-off changes the temperature of the water.
Let's think about temperature. Are bodies of water all the same temperature?
Streams that feed into larger streams and rivers and other bodies of water (higher order) are cooler than those into which they flow. Why? Because streams tend to start in higher elevations and are fed by cooler water or ice; there is also higher slope and speed and therefore more turbulance and therefore more evaporation which cools; they tend to be smaller and therefore are more easily and completely shaded by trees.
The ocean has warm and cold currents. Captains of fishing boats know just the right temperatures for specific kinds of fish, like swordfish, and compete with each other to find and get into position to do their fishing in the best place.
El Nino changes the pattern of cold and warm water, and new fish can invade old fishing areas.
Why might a change in temperature threaten life in the water?
Every organism has certain temperatures that are better for certain stages of life (laying eggs, migrating, for example). Temperature changes the water chemistry. Warm water holds less oxygen and some species need more oxygen. Here are two different kinds of salmon responding to slightly different temperature conditions.
Max for growth Best for Embryos Best for Spawning ATLANTIC SALMON 23 deg C /73 deg F 5 deg C/41 deg F 7 deg C, 45 deg F Coho SALMON 24/75 10/50 13/55
Water temperature is like a clock for aquatic organisms. It clues organisms about the time to reproduce, grow, and move to a new location. Some organisms are adapted to colder water (trout, salmon, and most stonefly nymphs), some are adapted to warmer water (carp, and most dragonfly nymphs). Most organisms become stressed in extremely hot or cold water and when water temperatures suddenly change (for instance, due to thermal pollution)." (Imagiworks) Extremes of temperature in their natural range can stress them. Species move, if they can, to find the optimal range. Big changes, like the pouring of material from an industry into the water) are stressors and can change the habitat altogether.
What about changes of light? What can affect light entering the water?
Changes of season can affect the amount of light reaching a certain piece of land. In addition, vegetation changes with season, and so shade over non-marine water changes. Shade also cools water. The amount of suspended material (cloudiness, turbidity) changes the amount of light that can reach certain depths in the water. Turbidity can be affected by natural erosion, rainfall, bottom feeder activity, algal blooms from nitrate run-off, flow. Particles absorb heat and so change habitats. Particles can provide a place for microorganisms to breed.Oil on the surface of the water can change which wave lengths reach which depths in the water. It has other effects too, making the water less "breathable."
Extensions: Design your own Cloudiness Tool. While more professional instruments will give more exact readings, this can give an approximation of turbidity.
Resources: Look at
NASA's Water Habitats as seen from space. DO NOT enlarge the pictures unless you absolutely sure you have room on your computer!
Benthic Invertebrates [http://rock.geo.csuohio.edu/norp/bmi.html]
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