STREAM ECOLOGY

ByMaggie Bell-McKinnon, biologist

Washington Department of EcologyEmail: MBEL461@ecy.wa.gov

Why Should We Care About Streams?

Wildlife drink water out of streams.

We like to fish and swim in streams.

Fish and other aquatic animals need good water quality for their homes and for their food.

Stream Structure

Pool

Riffle

Run or Glide

Woody Debris

Stream Discharge - is the total amount (volume) of water flowing in the stream.It is important to know how much water is flowing in a stream because it affects many things about a stream, for example:

* Salmon need slower flowing areas of a stream to lay their eggs.

* Other aquatic animals (like macroinvertebrates) and algae can’t live in a stream that has water moving too fast.

Stream Discharge – how to measure

Stream discharge is measured by multiplying the area of the stream by its velocity.

Stream discharge is measured in cubic feet per second (cfs).

Depth

Width

A Pretend Stream

Stream Discharge = Area (A) x Velocity (V)

Area (A) = Depth x Width

A Real Stream

34 5 6 7 8 9

101

Stream Area = the area of box 1+box 2+box 3+box 4+box 5+box 6+box 7+box 8+box 9+box 10

Embeddedness• Embeddedness refers to how much the rocks (gravel,

cobble, and boulders) are surrounded by, covered, or sunken into the silt, sand, or mud of the stream bottom.

Embeddedness• Generally, as rocks become embedded, fewer living

spaces are available to macroinvertebrates and fish for shelter, spawning and egg incubation.

Riparian Zone• The area between the stream and the land

away from the stream.• Riparian comes from the Latin word, ripa,

which means river bank.• Because the riparian zone can flood, the

vegetation that grows there must be able to tolerate having its roots get wet occasionally.

Riparian zones are important to a stream because:

• They filter pollutants and prevent them from entering the stream

Riparian zones are important to a stream because:

• They prevent the streambank from eroding or wearing away.

Riparian zones are important to a stream because:

• They supply shade to the stream

Riparian zones are important to a stream because:

• They provide shelter and food for animals that live in or near the stream

Examples of Riparian Vegetation

• In a healthy riparian zone, there are typically three layers of vegetation that occur:Tall treesShorter trees and shrubsFlowering plants and ferns

Douglas fir - Pseudotsuga menziesii

Black cottonwood - Populus trichocarpa

Vine maple - Acer circinatum

Devil’s club - Oplopanax horridus

Slough sedge - Carex obnupta

Food Web

Food Web

The Sun

Food Web

Food Web

Food Web

Food Web

Food Web

Black Fly Larvae

Black Fly Larvae on a Rock

Food WebCaddis Fly Larvae

Food Web

Caddis Fly Larvae

Food Web

Water Louse

Food Web

Water Strider

Food Web

Food Web

Food Web

Water Quality ParametersDissolved Oxygen• Oxygen in the water comes from the air/ atmosphere and the

aquatic plants (through photosynthesis).

Water Quality ParametersDissolved Oxygen

• Aquatic organisms – plants and animals – need to breathe oxygen, just like people.

Water Quality ParametersDissolved Oxygen• Dissolved oxygen levels change throughout the day based on

water temperature and photosynthetic activity.

4

6

8

10

12

14

16

8/22/03 15:00 8/23/03 6:00 8/23/03 21:00 8/24/03 12:00 8/25/03 3:00 8/25/03 18:00 8/26/03 9:00

pH (

pH u

nits

), D

O (

mg/

L),

Tem

p (C

)

0

50

100

150

200

SpC

(us/

cm)

Temp pH DO Winklers SpC

Water Quality ParametersTemperature

• Stream temperature controls how plants and animals live.• Warm water contains less dissolved oxygen than cool

water.

Water Quality ParametersTemperature• Young salmon need temperatures of around 9°Centigrade;

adult salmon need water that’s 12°Centigrade.

Water Quality ParameterspH• A pH measurement tells us

whether a stream is acidic or alkaline.

• pH values range from 0 to 14; values from 0 to 7 are considered acidic, 7 is neutral and above 7 is considered alkaline or basic.

• The pH of a stream is determined by what kind of rocks the stream flows over and sometimes by humans.

Representative pH values

Substance pH

Stomach Acid 1.5 – 2.0

Cola 2.5

Vinegar 2.9

Orange Juice 3.5

Coffee 5.0

Healthy Skin 5.0

Urine 6.0

Pure Water 7.0

Health Human Saliva 6.5 - 7.4

Blood 7.3 – 7.5

Seawater 7.7 – 8.3

Baking Soda 8.4

Hand Soap 9.0 – 10.0

Bleach 12.5

Water Quality ParametersNutrients

• Nitrate is one of the nutrients which is used as food by plants .

• Nitrates can come from decomposing plants and animals, human sewage, fertilizers and stormwater run-off.

• Excessive amounts of nitrates can cause too much algae growth. This lowers the dissolved oxygen levels when the algae die and decompose.

Water Quality ParametersTurbidity• Turbidity is a measurement of

how clear or cloudy the water looks. Water becomes cloudy when it contains solid material.

• This solid material can be a combination of sediment, algae, aquatic animals - anything that can be suspended in the water.

• Turbidity can affect the ability of fish to live by clogging their gills.

Water Quality ParametersBacteria• Not all bacteria are harmful

to humans but some are, like fecal coliform. These “bad” bacteria produce toxins which make people sick.

• It is important to protect humans from these harmful bacteria which could occur both in our drinking water as well as in the lakes and rivers where people play and have fun.

What can you do to help a stream?