What’s living in Bear Creek?
Service
Learning
Overview
Students will learn how to collect macroinvertebrate samples
from Bear Creek, observe specimens and acquire basic
information about their forms, functions and ecological
importance. For the service component, students will assist in
caring for riparian vegetation. Activities may include
watering, weeding, mulching etc.
Grade Level
Time
3rd - 12th
60 - 90 minutes
Service Tie-in
By caring for riparian vegetation, more plant material will reach the stream where it can become food for
aquatic insects. A healthy riparian canopy also keeps water temperatures cool and filters out pollutants.
Oregon State Standards
S.3.3S.2 Use the data collected from a scientific investigation to explain the results and draw conclusions.
S.4.2L.1 Describe the interactions of organisms and the environment where they live.
S.4.3S.2 Summarize the results from a scientific investigation and use the results to respond to the question
being tested.
S.7.2L.2 Explain the processes by which plants and animals obtain energy and materials for growth and
metabolism.
S.H.3S.3 Analyze data and identify uncertainties. Draw a valid conclusion, explain how it is supported by the
evidence and communicate the findings of a scientific investigations.
Background
Aquatic insects
There are two terms often used to describe the tiny organisms that make up the base of the food chain in rivers
and streams: macroinvertebrates and aquatic insects. Aquatic insects are insects that are specialized to live in
water for at least one stage of their life. A large number of aquatic insects fall into the category of
macroinvertebrates: macro means it is big enough to see with the naked eye and invertebrate refers to the lack of
spinal column/backbone. Instead of having a skeletal system comparable to humans (endoskeleton) and other
vertebrates, invertebrates have rigged armor like outer bodies (exoskeletons) to give their bodies shape. The term
macroinvertebrate includes insects but also crustaceans (such as crayfish), mollusks (such as aquatic snails), and
aquatic worms. This means that the term macroinvertebrates includes aquatic insects but is not limited to just
aquatic insects.
Where do aquatic macroinvertebrates live?
Aquatic macroinvertebrates are found in many
different types of aquatic environments: lakes,
streams, ponds, marshes and puddles. Most aquatic
macroinvertebrates are benthic (dwelling at the
bottom) and usually will not be found at the water’s
surface. These benthic creatures have very specialized
bodies; some have compressed or flat bodies so they
can creep beneath stones or in crevasses. Small size
also allows insects to enter and move in small spaces.
Some insects have specialized attachment devices
that allow them to cling to rocks and other
material at the bottom. These devices
include tiny hooks, suckers and
hairy mats on the ends of their
legs. Some organisms secrete
sticky substances or web-like
devices to keep them fixed to
the substrate.
Why are they important?
Aquatic macroinvertebrates play a key role in helping
to maintain the health of the water ecosystem where
they live by eating bacteria and dead, decaying plants
and animals. Overall water quality affects which types
of organisms can survive in a body of water. Water
quality may be assessed by looking at the amount of
dissolved oxygen, the levels of algal growth,
pollutants, and pH levels.
How do they handle disturbance?
The health of a stream system is directly tied to
disturbance, both natural and manmade. The timing
and magnitude of natural disturbance (e.g., floods,
drought, and photoperiod) is critical to maintaining
the ecological functions of a stream system.
For example, insect productivity may increase
following a flood and the associated influx of energy
inputs. Increased insect productivity, in turn, results
in increased fish growth and abundance. Human
disturbance, on the other hand, often has a
detrimental impact on a stream’s ecological functions.
Sedimentation, water withdrawals, channelization,
heavy metals from mine tailings, stormwater
discharge, and riparian zone loss are some of the
potential threats. Through
direct changes to stream
habitat or alterations to
energy processing,
human-induced impacts
ultimately lead to
changes in a stream’s
macroinvertebrate
community.
What can macros tell us about water quality?
The biological response to stream impacts may be the
greatest contribution aquatic insects make from the
standpoint of natural resource management. Just like
fish, aquatic insects are excellent indicators of stream
health. Some species of mayflies are sensitive to heavy
metal contamination. Many stoneflies cannot
tolerate silt or thermal pollution, whereas an overabundance of fly and midge larvae may indicate
multiple stressors. Many tools, techniques, and models
exist to evaluate changes in macroinvertebrate
communities. Regardless of the methodology, the
concept remains the same: macroinvertebrate communities in healthy streams should differ from macroinvertebrate communities in impacted streams.
Measuring and evaluating these differences has been
the focus of many water resource agencies. A recent
report by the U.S. Environmental Protection Agency
indicated that nearly every state water quality
agency in the U.S. uses aquatic insects to some degree
in evaluating surface water quality. Given the
importance of clean water and healthy streams,
aquatic insects certainly play a large role for such
small creatures.
Reasons why macroinvertebrates are used as water
quality indicators:
•
They are sensitive to changes in the
ecosystem.
•
Many live in an aquatic ecosystem for over
one year.
•
They cannot easily escape changes in the
water quality.
•
They can be collected very easily from most
aquatic systems with inexpensive or home
made equipment.
Vocabulary
macroinvertebrate, benthic, water ecosystem, water
quality, species, detritus
Site
At North Mountain Park there is a safe access to Bear
Creek at a nice riffle area for sampling. There is also a
small open area next to the access for setting up tables
and equipment. Any stream with safe access and
flows could be used for this program if there is also
room to set up portable tables and equipment.
how these water animals qualify as
macroinvertebrates (animals without spinal
columns).
Materials
D net/kick net
Tray
Ice cube tray
Insect ID cards
Guide to Pacific Northwest Aquatic Invertebrates
Pictures of insects
Data sheets
Pencils & clipboards (?)
Magnifying viewers
Stopwatch
3)
Macroinvertebrates thrive in healthy waters.
Tell students that they are going to see how
healthy/clean the water in Bear Creek is by
collecting macroinvertebrates. Ask them if
they can guess how their findings will help
them to determine this.
4)
Tell students that if they find a lot of different
kinds of macroinvertebrates living in Bear
Creek today, they will know that the water is
relatively clean, meaning that the water
quality is high. Introduce them to pollution
intolerant species such as the stonefly, and to
more tolerant species like the backswimmers.
Explain that they will primarily be looking for
benthic (bottom-dwelling) macroinvertebrates.
5)
Describe the habitat and behavior of benthic
macros (anchored to rocks, gathers food from
swiftly moving waters, etc.). This discussion
should lead into methodology (how/where to
collect macroinvertebrates).
6)
Ask students to point to areas where they
think the macros might be living (should be
rocky). In addition to rocky places or places
with a lot of detritus (decaying organic
matter/food source), riffles (shallow, highly
oxygenated, rocky areas) are prime places to
look for macros.
7)
Introduce students to the tools they will be
using and demonstrate how to appropriately
gather samples and transfer them to viewing
stations as a team. (Be sure to remind
students to keep D nets/kick nets opened to
the current and flush with the stream
bottom).
Prior Preparation
Set up two tables with trays, viewers, droppers, cards
for two teams to examine samples.
Set up sampling gear next to the creek with an area for
students to change into boots or water sandals.
Collect a sample and put into two large viewing trays
(one per table) before students arrive.
Activity
Rough outline of time: Intro 5 min, methodology 5
min, divide students 10 min, examine samples 20
min, and wrap up 5 min.
1)
2)
Start off by brainstorming with the students and
ask them what they think lives in Bear Creek.
What about insects? Can you think of any insects that live in creeks? Show picture of familiar aquatic insects (water strider or water boatman), talk about the importance of insects and
their ecological niche, eating detritus and becoming food for fish and birds.
Introduce them to the term macroinvertebrate.
Macro means it’s big enough to see with the
naked eye and invertebrate refers to an animal
that does not have a spinal column/backbone.
Explain that aquatic insects are macroinvertebrates as are mollusks (hold up a picture of a
snail), crustaceans (hold up picture of a crayfish), and some worms. Ask them if they can see
*Important to stress that the macros collected
need to be handled with care, gently
removed from nets and quickly placed into
water-filled trays in a shady location for
viewing, and then gently returned to the
same area in the creek after 20-30 minutes.
8)
Gathering Samples: divide students into
groups (groups of three work nicely), with
one person counting off or with stopwatch,
one person turning rocks and/or scrubbing
rocks in front of net opening, and one person
holding the net. Have students switch roles
after every one-minute count, three rotations
should suffice.
9)
Examining Samples: Have students count the
total number of species gathered and the
number of each type. To help with this they can
transfer and divide collections into ice-cube
trays. They should be prompted to record
results on their group data sheet.
10)
Using the Aquatic Insect ID cards and the
“Guide to Pacific Northwest Aquatic
Invertebrates,” have them identify as many
macros as possible.
11)
Based on their findings, ask students to determine whether or not the water of Bear Creek is
clean (did any of the groups find macroinvertebrate species that are considered pollution intolerant? Were all of the species found tolerant
to pollution? Did they find a variety of species?). Conclusions should be recorded on the
group data sheet.
12)
Discuss findings and conclusions as a group.
Have students return their specimens to the
creek and assist with tool clean-up.
Sample Data Sheet
North Mountain Park Nature Center
620 N Mountain Ave ~ Ashland, OR 541.488.6606 ~ www.northmountainpark.org
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