A Little Bit More
We’re not suggesting that a shaded stream doesn’t have ANY plant life growing in these waterways, but in the Northeast, especially, there are many small streams that receive very little sunlight during the growing season and therefore support a minimal amount of plant life. However, once you factor in the enormous amount of plant material that falls into these waters in the fall, you realize that there really is plenty of food available for animals; it’s just in a different form than you might expect.
Limnologists view streams with a “stream continuum” in mind. As a stream increases in size and moves from its headwaters to more open and larger volume, the invertebrates living on the bottom change in response to a change in food availability. Initially, those invertebrates that can utilize the coarser material that falls into the headwater streams (leaves and twigs for the most part) are the most abundant. Then, as the particulate matter changes to finer materials, other kinds of invertebrates become more and more numerous and eventually dominate the stream.
Activities
Science – Check it out
Objectives: Apply what you learn in this unit to your local stream
Materials: Ability to travel to the nearest stream or digital camera
Since we’ve just discussed two different kinds of streams – one that is mostly shaded and one that is mostly sunny – why not see which one your local or closest stream is most like? I realize most students don’t have a stream on school property but often there is one nearby.
There are two options here:
Option #1 – have students travel to the nearest stream (size doesn’t matter as long as it has running water most of year). Once there you can look at the surrounding streamside (try to make sure that your location isn’t atypical of that stream) and estimate whether your stream is mostly a shaded stream or mostly a sunny stream. Which ever one you determine it seems most like, you can then look to see whether there is much leaf litter lying on the bottom (shaded stream) or much algae growing on the bottom (sunny stream). I recognize that many streams have been altered by human action so you’ll need to take this into consideration when assigning the “type” of stream you have.
Option #2 – Have a student or parent take some digital photos of the nearest stream and bring them to your school to share with the class. Once you all are able to look at the photos, you can decide whether your stream is a shaded stream or a sunny stream.
Key Concepts
Populations and Ecosystems, Food Webs /Food Pyramids
Questions
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