line graphic

menu graphic
  Home   Ecology   Pollution   Resources   Stream Flow   Food Webs   Dams   Saving endangered fishes   Plants and Animals

The Many Habitats a Stream Provides

     Even a small mountain stream provides an astonishing number of different places for animals to live, or habitats. The casual visitor would not see more than water and rocks, yet the stream is filled with unseen creatures. Where do they all live?

     Rocks provide several different habitats. There is the side that faces upriver: animals that are very good at clinging to rock will do well here. The side that faces downriver provides a certain degree of shelter from current, while still allowing an animal to hunt for food. The top of a rock, if it is contacting air in some places, will be a good place for animals that can't breathe underwater and need to surface now and then. Underneath the rock is a very popular place for animals who don't want to be eaten!

     Microhabitat describes very local habitats like this, the small spaces that are chosen by each organism. Some creatures make their own microhabitats. Many (but not all) caddisflies build cases about themselves. Other animals dig holes in banks or in the mud on the bottom.

     Fallen logs and branches (Large Woody Debris, or LWD), provide a place for some animals to burrow into and surfaces for others to attach themselves, as they might to a rock. They also create areas where small detritus such as leaf litter can pile up underwater. These piles of leaf litter are excellent shelter for many creatures, including hellgrammites (large, fiercely predaceous larvae of dobsonflies).

     Besides providing microhabitats, fallen logs, branches, rootwads, and even rocks perform the valuable service of clogging streams. A well-obstructed stream is a healthy one. Streams clogged with natural debris form countless small pools, waterfalls, and other features that provide habitat, as well as hiding places for young fish.

     There is other debris, leaf litter, and algae floating downstream, and animals cling to this or burrow into it, as well as eat it. Parasites make their host their habitat.

     Often the only way to determine what microhabitat an animal uses is by either catching it in the habitat (using intensive electroshocking while making many observations and measurements) or by observing it in its habitat. This may be done by looking beneath the water through a pane of glass, setting cameras in the water, or snorkeling.

Cross-Section of a Stream

water column graphic Surface


Benthic Zone

Hyporheic Zone
ausrufezeichen-0028.gif from
You can see the different parts of a river by running your mouse over the pictures or labels on this page. Clicking on what you see will give you a pop-up window that tells you what lives there. Remember to close the pop-up window before you click on anything else. Otherwise (depending on what browser you are using), it will end up behind your page!
fisch-0018.gif from

Longitudinal Section of a Stream

graphic of longitudinal section of stream Cascade





     The terms shown above in the pictures are habitat classifications. Others include side channel, which is a small area where water has left and then returned to the river, running parallel to the river, backwater, much like a side channel but with the upstream end blocked off, creating stagnant water, embayment, which you might say is almost like a backwater, but not nearly so extreme or cut off, and in which the water is still actively running, and plunge, an area where water runs off a submerged obstacle and creates a deep, though flowing, area on the other side of it (and still technically part of the run).

Top-Down View of a Stream

graphic of top-down view of stream
Cascade Falls Pool Embayment Run Plunge Riffle Backwater

     Finally, a stream's ecosystem includes the area immediately around the stream--the damp banks and vegetation on both sides, the trees that hang over it, the air above it. And it includes the stream's entire watershed as well.

ball graphic Read Following a River Wherever it Goes: Beneath the Surface of Mountain Streams
ball graphic An in-depth examination may be found in Aquifers and hyporheic zones: Towards an ecological understanding of groundwater

Reading listTo learn more about habitats, check out the reading list, where you will find some excellent references listed. (You will be able to order them from here, too).

menu graphic
Home   Books   Links   Habitat   Flow   Ecology   Plants & Animals   Food Webs   Science

Site Search

If you have comments or suggestions, email me at

Surface Water-column Benthic Zone Hyporheic Zone Cascade Waterfall Pool Run Riffle Cascade Waterfall Embayment Pool Plunge Backwater Riffle Run Plants and Animals The ecology of streams Rivers As Resources Stream Pollution Hydrology, and how streams flow Stream food webs The effects of dams Stream habitats Return to the first page Saving endangered fishes Return to the first page Plants and animals in the stream How a river flows The many kinds of homes in a stream or river Who is eating what--and whom! How biologists study streams and rivers The ecology of streams and rivers - how are they faring? Other places to go for information Books Links Habitat Flow Ecology Plants& Animals Food Webs Science Home