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4.2 Streamside Biosurvey
The Streamside Biosurvey is based on the simple
macroinvertebrate sampling approach developed and used by the
Ohio Department of Natural Resources and the Izaak Walton League
of America's Save Our Streams program and adapted by many
volunteer monitoring programs throughout the United States.
This assessment approach has two basic components. The first
is a biosurvey of aquatic organisms that involves collecting and
identifying macroinvertebrates in the field and calculating an
index of stream quality. The second is the habitat
characterization method known as the Streamside Biosurvey
Habitat Walk.
Two methods of macroinvertebrate sampling are detailed in this
section one for rocky-bottom streams (using a kick net) and one
for muddy-bottom streams (using a dip net). Figure 4.7 illustrates and describes the nets used
for these assessments. Both of these aquatic organism collection
procedures have been widely tested and used successfully by many
groups. You should consult with a local aquatic scientist to
determine which method is appropriate for streams in your
area.
Note
The Streamside Biosurvey is based on protocols developed and
widely used by programs such as the Ohio Department of Natural
Resources, the Izaak Walton League of America, and others. This
manual recommends some modifications to their established
protocols. These include:
-
A finer mesh size for the kick and dip nets used to sample for
macroinvertebrates
-
In rocky-bottom streams, compositing three samples into one
before identifying macroinvertebrates rather than identifying
macroinvertebrates in three separate samples and choosing the
best result. Compositing generally provides a more representative
sample of the macroinvertebrate community than a discrete sample
taken from one part of the riffle. Riffle areas have what is
known as a patchy distribution of organisms, meaning that
different types of organisms are naturally found in different
parts of the riffle. In order to more accurately assess the
macroinvertebrate community in a rocky-bottom stream site, it is
important to take a representative sample that includes organisms
found in different microhabitats—such as in different parts
of the riffle or in riffles of various flows and depths.
-
A new method for calculating the stream quality rating. This
modification incorporates a weighting factor to take into account
the abundance of organisms in each pollution tolerance category
(pollution-sensitive, somewhat tolerant, and tolerant).
-
In muddy-bottom streams, varying how much each habitat type is
sampled depending on its abundance at the sampling site.
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Like the Stream Habitat Walk described in Section 4.1, the
Streamside Biosurvey is useful as a screening tool to identify
water quality problems and as an educational tool to teach
volunteers about pollution and stream ecology. But instead of
randomly picking up rocks or sticks and brushing off
macroinvertebrates for simple observation purposes, Streamside
Bio-survey volunteers are trained to use special nets and
standardized sampling protocols to collect organisms from a
measured area of stream habitat. Volunteers identify collected
organisms, usually to the order level, and sort them into
taxonomic groups based on their ability to tolerate pollution.
Using this information, volunteers can then calculate a simple
stream quality rating of good, fair, or poor.
Because the Streamside Biosurvey involves a standardized
sampling protocol, a basic level of training, professional
assistance, and a simple stream rating based on macroinvertebrate
diversity and abundance, this approach is more effective than the
Stream Habitat Walk in characterizing stream health and
determining general water quality trends over several years.
However, this method is not generally suited to determining
subtle pollution impacts due, in part, to its uncomplicated level
of macroinvertebrate identification and analysis. This, of
course, is also one of the Streamside Biosurvey's greatest
strengths, since volunteers can be easily trained in its
methods.
Key features of the Streamside Biosurvey are as follows:
-
It includes the Streamside Biosurvey Habitat Walk as its
physical habitat characterization and visual biological
characterization components. This protocol is a somewhat more
detailed version of the Stream Habitat Walk described in Section
4.1.
-
It centers around a macroinvertebrate survey in which
organisms are collected according to specific protocols,
identified in the field (generally to taxonomic order), and are
then released back into the stream.
-
For the identification process, volunteers group
macroinvertebrates into three categories based on their pollution
tolerance or sensitivity. Volunteers then calculate a water
quality index by counting the specimens in each sensitivity
category and determining whether they are rare, common, or
dominant; multiplying the number of taxa in each category by a
weighting factor; adding all the scores; and comparing results to
a water quality rating scale that has been determined by a
locally knowledgeable biologist/ecologist.
-
The Streamside Biosurvey requires some equipment and training.
Training can be conducted at the stream site, although some
advance preparation is required. For example, a biologist with
regional experience should assist in developing the
macroinvertebrate key and the tolerance category groupings on the
field data sheets. A reference collection is recommended to help
volunteers identify macroinvertebrates.
Step 1 Prepare for the Streamside Biosurvey field
work
Much of the preparation work for this approach is similar to
that of the Stream Habitat Walk (section 4.1). Refer back to that
section for relevant information on the following tasks:
-
Scheduling the biosurvey
-
Obtaining a USGS topographical map
-
Selecting and marking monitoring locations
-
Becoming familiar with safety procedures
TASK 1 Gather tools and equipment for the Streamside
Biosurvey
In addition to the basic equipment listed in Section 2.4, you
should collect the following equipment needed for the
macroinvertebrate collection of the Streamside Biosurvey:
-
Vial with tight cap filled about one-half full with 70 percent
ethyl alcohol
-
Buckets (2)
-
Hand lens, magnifying glass, or field microscope
-
Tweezers, eyedropper, or spoon
-
Plastic bag
-
Large, shallow, white pans, such as dishpans (2)
-
Spray water bottle
-
Plastic ice cube tray
-
Taxonomic key to aquatic organisms
-
Calculator
- For rocky-bottom streams
--Kick net, a fine mesh (500 µm) nylon net approximately
3x3 feet with a 3-foot long supporting pole on each side is
recommended--Figure 4.7).
- For muddy-bottom streams
--D-frame net (a dip net with a frame 12 inches wide with a
fine nylon mesh, usually about 500 µm, attached to the
frame).
Step 2 Collect and Sort Macroinvertebrates
The method you use to collect macroinvertebrates using this
approach depends on the type of stream you are sampling.
Rocky-bottom streams are defined as those with bottoms made up of
gravel, cobbles, and boulders in any combination and usually have
definite riffle areas. Riffle areas are fairly well oxygenated
and, therefore, are prime habitats for benthic
macroinvertebrates. In these streams, use the rocky-bottom
sampling method.
Muddy-bottom streams have muddy, silty, or sandy bottoms and
lack riffles. Generally, these are slow moving, low-gradient
streams (i.e., streams that flow along relatively flat terrain).
In such streams, macroinvertebrates generally attach themselves
to overhanging plants, roots, logs, submerged vegetation, and
stream substrate where organic particles are trapped. In these
streams, use the muddy-bottom sampling method.
Both methods are detailed below. Regardless of which
collection method is used, the process for counting, identifying,
and analyzing the macroinvertebrate sample for the Streamside
Biosurvey is the same.
Rocky-Bottom Sampling Method
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Use the following method of macroinvertebrate sampling in
streams that have riffles and gravel/cobble substrates. You will
collect three samples at each site and composite (combine) them
to obtain one large total sample.
TASK 1 Identify the sampling location
You should have already located your site on a map along with
its latitude and longitude (see Task 3,
in Section 4.1 - Stream Habitat Walk).
Figure 4.8
Location of sample sites in a rocky-bottom stream
with riffles
Within a 100 yard reach volunteers begin their sampling at the
most downstream site and then work their way upstream.
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-
You are going to sample in three different spots within a
100-yard stream reach. These spots may be three separate riffles;
one large riffle with different current velocities; or, if no
riffles are present, three run areas with gravel or cobble
substrate. Combinations are also possible (if, for example, your
site has only one small riffle and several run areas).
Mark off your 100-yard stream reach. If possible, it should
begin at least 50 yards upstream of any human-made modification
of the channel, such as a bridge, dam, or pipeline crossing,
Avoid walking in the stream, since this might dislodge
macroinvertebrates and alter your sampling results.
-
Sketch the 100-yard sampling area. Indicate the location of
your three sampling spots on the sketch. Mark the most downstream
site as Site 1, the middle site as Site 2, and the upstream site
as Site 3. (See Fig. 4.8.)
TASK 2 Get into place
-
Always approach your sampling locations from the downstream
end and sample the site farthest downstream first (Site 1) (see
Fig. 4.9, Panel #1). This minimizes the
possibility of biasing your second and third collections with
dislodged sediment or macroinvertebrates.
Always use a clean kick net, relatively free of mud and debris
from previous uses. Fill a bucket about one third full with
stream water and fill your spray bottle.
-
Select a 3-foot by 3-foot riffle area for sampling at Site 1.
One member of the team, the net holder, should position the net
at the downstream end of this sampling area. Hold the net handles
at a 45 degree angle to the water's surface (see Fig. 4.9, Panel #2). Be sure that the bottom of the
net fits tightly against the stream-bed so no macroinvertebrates
escape under the net. You may use rocks from the sampling area to
anchor the net against the stream bottom. Don't allow any
water to flow over the net.
TASK 3 Dislodge the macroinvertebrates
-
Pick up any large rocks in the 3-foot by 3-foot sampling area
and rub them thoroughly over the partially-filled bucket so that
any macroinvertebrates clinging to the rocks will be dislodged
into the bucket (see Fig. 4.9, Panel #3).
Then place each cleaned rock outside of the sampling area. After
sampling is completed, rocks can be returned to the stretch of
stream they came from.
-
The member of the team designated as the "kicker"
should thoroughly stir up the sampling area with their feet,
starting at the upstream edge of the 3-foot by 3-foot sampling
area and working downstream, moving toward the net. All dislodged
organisms will be carried by the stream flow into the net (see Fig. 4.9, Panel #4). Be sure to disturb the
first few inches of stream sediment to dislodge burrowing
organisms. As a guide, disturb the sampling area for about 3
minutes, or until the area is thoroughly worked over.
-
Any large rocks used to anchor the net should be thoroughly
rubbed into the bucket as above.
TASK 4 Remove the net
-
Next, remove the net without allowing any of the organisms it
contains to wash away. While the net holder grabs the top of the
net handles, the kicker grabs the bottom of the net handles and
the net's bottom edge. Remove the net from the stream with a
forward scooping motion (see Fig. 4.9,
Panel #5).
-
Roll the kick net into a cylinder shape and place it
vertically in the partially filled bucket. Pour or spray water
down the net to flush its contents into the bucket (see Fig. 4.9, Panel #6). If necessary, pick debris and
organisms from the net by hand. Release back into the stream any
fish, amphibians, or reptiles caught in the net.
TASK 5 Collect the second and third samples
Once you have removed all the organisms from the net repeat
these tasks at Sites 2 and 3. Put the samples from all three
sites into the same bucket. Combining the debris and organisms
from all three sites into the same bucket is called
compositing.
Hint: If your bucket is nearly full of water
after you have washed the net clean, let the debris and organisms
settle to the bottom of the bucket. Then cup the net over the
bucket and pour the water through the net into a second bucket.
Inspect the water in the second bucket to be sure no organisms
came through.
TASK 6 Sort macroinvertebrates
Pour the contents of the bucket into a large, shallow, white
pan. Add some stream water to the pan, and fill the ice cube tray
with stream water. Using tweezers, eye dropper, or spoon, pick
through the leaf litter and organic material looking for anything
that swims, crawls, or seems to be hiding in a shell, like a
snail. Look carefully; many of these creatures are quite small
and fast-swimming. Sort similar organisms into the ice cube
tray.
Note: Instructions for counting, identifying,
and analyzing the macroinvertebrate sample follow the
muddy-bottom sampling method. (See Step 3)
Muddy-Bottom Sampling Method
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Picking Bugs
Some monitoring programs find it easier to collect organisms
from the net by hand-picking them rather than washing the sample
into a pan and then trying to pick through the floating debris.
The advantage to placing the organisms in a pan is that they are
more likely to survive while in the pan and their characteristic
movements will help in organism identification.
If you prefer to pick bugs directly off the net, a white
background, such as a white plastic trash bag under the net, will
help you see the bugs more clearly. In addition, periodically
wetting the net with a water bottle will help keep the bugs alive
and moving.
Identification can be made easier if you sort the organisms
into groups based on physical similarities and place them
together in sections of an ice cube tray as you pick them from
the pan or net.
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In muddy-bottom streams, as in rocky- bottom streams, the goal
is to sample the most productive habitats available and look for
the widest variety of organisms. The most productive habitats are
the ones that harbor a diverse population of pollution
sensitive-macroinvertebrates. Volunteers should sample by using a
D-frame net to jab at the habitat and scoop up the organisms that
are dislodged. The objective is to collect a combined sample from
20 jabs taken from a variety of habitats.
TASK 1 Determine which habitats are present
Muddy-bottom streams usually have four habitats (Fig. 4.10).
It is generally best to concentrate sampling efforts on the most
productive habitat available, yet to sample other principal
habitats if they are present. This ensures that you will secure
as wide a variety of organisms as possible. Not all habitats are
present in all streams or present in significant amounts. If your
sampling areas have not been preselected, try to determine which
of the following habitats are present. (Avoid standing in the
stream while making your habitat determinations.)
Figure 4.10
Four habitats found in muddy-bottom
streams
Volunteers will likely find the most macroinvertebrates in
vegetated habitats and snags and logs.
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- Vegetated bank margins.
This habitat consists of overhanging bank vegetation and
submerged root mats attached to banks. The bank margins may also
contain submerged, decomposing leaf packs trapped in root wads or
lining the streambanks. This is generally a highly productive
habitat in a muddy_bottom stream, and it is often the most
abundant type of habitat.
- Snags and logs.
This habitat consists of submerged wood, primarily dead trees,
logs, branches, roots, cypress knees and leaf packs lodged
between rocks or logs. This is also a very productive
muddy-bottom stream habitat.
- Aquatic vegetation beds and decaying organic matter.
This habitat consists of beds of submerged, green/leafy plants
that are attached to the stream bottom. This habitat can be as
productive as vegetated bank margins, and snags and logs.
- Silt/sand/gravel substrate.
This habitat includes sandy, silty, or muddy stream bottoms;
rocks along the stream bottom; and/or wetted gravel bars. This
habitat may also contains algae-covered rocks (sometimes called
Aufwuchs). This is the least productive of the four muddy-bottom
stream habitats, and it is always present in one form or another
(e.g., silt, sand, mud, or gravel might predominate).
TASK 2 Determine how many times to jab in each habitat
type
Your goal is to jab a total of 20 times. The D-frame net is 1
foot wide, and a jab should be approximately 1 foot in length.
Thus, 20 jabs equals 20 square feet of combined habitat.
-
If all four habitats are present in plentiful amounts, jab the
vegetated banks 10 times and divide the remaining 10 jabs among
the remaining 3 habitats.
-
If three habitats are present in plentiful amounts and one is
absent, jab the silt/sand/gravel substrate the least productive
habitat 5 times and divide the remaining 15 jabs among the other
two more productive habitats.
-
If only two habitats are present in plentiful amounts, the
silt/sand/gravel substrate will most likely be one of those
habitats. Jab the silt/sand/gravel substrate 5 times and the more
productive habitat 15 times.
-
If some habitats are plentiful and others are sparse, sample
the sparse habitats to the extent possible, even if you can take
only one or two jabs. Take the remaining jabs from the plentiful
habitat(s). This rule also applies if you cannot reach a habitat
because of unsafe stream conditions. Jab a total of 20 times.
Because you might need to make an educated guess to decide how
many jabs to take in each habitat type, it is critical that you
note, on the field data sheet, how many jabs you took in each
habitat. This information can be used to help characterize your
findings.
TASK 3 Get into place
Outside and downstream of your first sampling location (1st
habitat), rinse the dip net and check to make sure it does not
contain any macroinvertebrates or debris from the last time it
was used. Fill a bucket approximately one-third full with clean
stream water. Also, fill the spray bottle with clean stream
water. This bottle will be used to wash down the net between jabs
and after sampling is completed.
This method of sampling requires only one person to disturb
the stream habitats. While one person is sampling, a second
person should stand outside the sampling area, holding the bucket
and spray bottle. After every few jabs, the sampler should hand
the net to the second person, who then can rinse the contents of
the net into the bucket.
TASK 4 Dislodge the macroinvertebrates
Approach the first sample site from downstream, and sample as
you walk upstream. Here is how to sample in the four habitat
types:
-
Sample vegetated bank margins by jabbing vigorously, with an
upward motion, brushing the net against vegetation and roots
along the bank. The entire jab motion should occur
underwater.
-
Figure 4.11
Collecting a sample from a log
Volunteer rubs the log with one hand and catches dislodged
organisms and other material in the net.
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-
To sample snags and logs, hold the net with one hand under the
section of submerged wood you are sampling. With the other hand
(which should be gloved), rub about 1 square foot of area on the
snag or log. Scoop organisms, bark, twigs, or other organic
matter you dislodge into your net. Each combination of log
rubbing and net scooping is one jab (Fig. 4.11).
-
To sample aquatic vegetation beds, jab vigorously, with an
upward motion, against or through the plant bed. The entire jab
motion should occur underwater.
-
To sample a silt/sand/gravel substrate, place the net with one
edge against the stream bottom and push it forward about a foot
(in an upstream direction) to dislodge the first few inches of
silt, sand, gravel, or rocks. To avoid gathering a netful of mud,
periodically sweep the mesh bottom of the net back and forth in
the water, making sure that water does not run over the top of
the net. This will allow fine silt to rinse out of the net.
When you have completed all 20 jabs, rinse the net thoroughly
into the bucket. If necessary, pick any clinging organisms from
the net by hand and put them in the bucket.
TASK 5 Sort the macroinvertebrates
Pour the contents of the bucket (water, organisms, and organic
material) into a large, shallow, white pan and fill the ice cube
tray with clean stream water. Using tweezers, eye dropper, or
spoon, pick through the leaf litter and organic material looking
for anything that swims, crawls, or seems to be hiding in a shell
(like a snail). Look carefully; many of these creatures are quite
small and fast-swimming. Sort similar organisms into the plastic
ice cube tray.
Step 3 Identify Macroinverte-brates and Calculate Stream
Rating
The following methods are used for both the rocky- and
muddy-bottom assessments.
Task 1 Identify Macroinvertebrates
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Identify the collected macroinvertebrates. Using the hand lens
or magnifying glass and the aquatic organism identification key,
carefully observe the collected macroinvertebrates. Refine your
initial sort so that like individuals are placed in the same
section(s) of the ice cube tray. If you cannot identify an
organism, place one or two specimens in the alcohol-filled vial
and forward it to your program coordinator for
identification.
-
On your field data sheet, note the number of individuals of
each type of organism you have identified (Section 3 of the field
data sheet See Fig. 4.12.).
-
Note: When you feel that you have identified
all the organisms to the best of your ability, return the
macroinvertebrates to the stream.
-
Assign one of the following abundance codes to each type of
organism. Record the code next to the actual count on the field
data sheet.
R (rare)
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=
|
if 1-9 organisms are found in the sample
|
C (common)
|
=
|
if 10-99 organisms are found in the sample
|
D (dominant)
|
=
|
if 100 or more organisms are found in the sample
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Your field data sheet should be organized to help you sort
macroinvertebrates into three groups based on their ability to
tolerate pollution. A local authority (such as a state
biologist or entomologist) should determine which organisms
belong in each pollution tolerance category for your
region.
Generally, the three tolerance groups are as follows:
- Group I
(sensitive organisms) includes pollution- sensitive organisms
such as mayflies, stoneflies, and non net-spinning caddisflies,
which are typically found in good-quality water.
- Group II
(somewhat sensitive organisms) includes somewhat
pollution-tolerant organisms such as net-spinning caddisflies,
crayfish, sowbugs, and clams, found in fair-quality water.
- Group III
(tolerant organisms) includes pollution-tolerant organisms
such as worms, leeches, and midges, found in poor-quality
water.
TASK 2 Calculate the stream quality rating
The stream water quality rating takes into account the
pollution sensitivity of the organisms and their relative
abundance. This is accomplished through use of a weighting
system.
The weighting system acknowledges the most desirable
combinations of pollution sensitivity and abundance by assigning
these extra weights within a 5, 3, and 1 point scale.
Pollution-sensitive organisms receive a weighting factor based on
a 5-point scale.
Somewhat sensitive organisms are weighted on a 3-point scale,
and tolerant organisms are weighted on a 1-point scale. As can be
seen in Table 4.2, a sample's ideal combination of organisms
would be "sensitive" and "somewhat sensitive"
organisms in common abundance (10-99 organisms), and pollution
"tolerant" organisms in rare abundance (less than 10
organisms). This is because it is never ideal for any given type
of organism to dominate a sample, and because it is best to have
a wide variety of organisms including a few pollution-tolerant
individuals.
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Add the number of R's, C's and D's in each of the
3 pollution tolerance groupings. Then, for each grouping,
multiply the total number of R's, C's and D's by the
relevant weighting factor. Table 4.3 illustrates sample
calculations for determining the water quality rating for
(hypothetical) Volunteer Creek.
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Note: The tolerance category groupings shown
on the Biosurvey Data Sheet were developed for streams in the
mid-Atlantic (Maryland, Virginia, West Virginia, District of
Columbia, Pennsylvania). These groupings may not totally apply in
other regions of the United States. It is important that
a local aquatic biologist take a look at these categories and
make any changes necessary for your region.
In addition, depending on the level of taxonomic training
volunteers receive, you might consider separating out some other
families of organisms. For instance, the tolerance groupings
given here separate caddisflies into net-spinning and non
net-spinning families. Mayflies might also be separated into
different tolerance groupings. It is not recommended here,
however, because of the difficulty in distinguishing mayfly
families in the field without a microscope.
Some volunteer programs, like the one coordinated by the
Audubon Naturalist Society in Maryland, conduct intensive field
identification training workshops and teach volunteers to
distinguish several families in the field. Creating more specific
tolerance groupings may be an option for your program if you have
the resources and expertise to conduct more intensive taxonomic
field training.
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To obtain a water quality rating for the site, total the
values for each group and add them together. The total score for
the sample stream site is: 16.2 (Group I) + 19.0 (Group II) + 2.3
(Group III) = 37.5.
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The final step is to compare the score to water quality
ratings (good to poor) established by a trained biologist
familiar with local stream fauna. Table 4.4 presents a tentative
rating scale for streams in Maryland. Assuming Volunteer Creek is
located in Maryland, the stream would receive a rating of
"Fair."
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Note: In addition to adjusting the rating
scale according to regional location, it might also need to be
adjusted for muddy-bottom vs. rocky-bottom streams. An
experienced stream biologist can calculate the best rating system
for your area's streams by examining data from several
streams.
Abundance |
Weighting
Factor |
Table 4.2
Weighting factors used in calculating stream water
quality ratings
|
|
Group I
Sensitive
|
Group II
Somewhat Sensitive
|
Group III
Tolerant
|
Rare (R)
|
5.0
|
3.2
|
1.2
|
Common (C)
|
5.6
|
3.4
|
1.1
|
Dominant (D)
|
5.3
|
3.0
|
1.0
|
Group I
Sensitive |
Group II
Somewhat Sensitive |
Tolerant |
Table 4.3
Sample calculations of index values for Volunteer
Creek
|
1 (No. of R's) x 5.0 = 5.0
2 (No. of C's) x 5.6 = 11.2
|
3 (No. of R's) x 3.2 = 9.6
1 (No. of C's) x 3.4 = 3.4
2 (No. of D's) x 3.0 = 6.0
|
1 (No. of R's) x 1.2 = 1.2
1 (No of C's) x 1.1 = 1.1
|
Index Value for Group I = 16.2
|
Index Value for Group II = 19.20
|
Index Value for Group III = 2.3
|
Score |
Rating |
Table 4.4
Tentative rating scale for streams in
Maryland
|
>40
20-40
<20
|
Good
Fair
Poor
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In a healthy stream, the sensitive (Group I) organisms will be
well represented in a sample. It is important to remember that
macroinvertebrate populations can fluctuate seasonally and that
these natural fluctuations can affect your results. Therefore, it
is best to compare the results by season from year to year.
(Compare your spring sampling results to each other, not to fall
results.)
Step 4 Conduct the Streamside Biosurvey: Habitat
Walk
You will conduct a habitat assessment (which will include
measuring general characteristics and local land use) in a
100-yard section of stream that includes the riffles from which
organisms were collected.
TASK 1 Delineate the habitat assessment boundaries
-
Begin by identifying the most downstream riffle that was
sampled for macroinvertebrates. Using your tape measure or twine,
mark off a 100-yard section extending 25 yards below the
downstream riffle and about 75 yards upstream.
-
Complete the identifying information on your field data sheet
for your habitat assessment site. On your stream sketch, be as
detailed as possible, and be sure to note which riffles were
sampled.
TASK 2 Complete the Physical Characteristics, Local Watershed
Characteristics, and Visual Biological Survey sections of the
field sheet
For safety reasons as well as to protect the stream habitat,
it is best to estimate these characteristics rather than actually
wading into the stream to measure them.
In-stream Characteristics
Figure 4.13
Overview and cross sections of a pool, riffle, and
run
Varying flows and depths create a variety of habitats for
macroinvertebrates.
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- Pools, riffles, and runs
create a mixture of flows and depths and provide a variety of
habitats to support fish and invertebrate life. Pools are deep
with slow water. Riffles are shallow with fast, turbulent water
running over rocks. Runs are deep with fast water and little or
no turbulence.
- Stream bottom (substrate)
is the material on the stream bottom. Identify what substrate
types are present. Substrate types include:
-
- Silt/clay/mud
--This substrate has a sticky, cohesive feeling. The particles
are fine. The spaces between the particles hold a lot of water,
making the sediments behave like ooze.
- Sand (up to 0.1 inch)
--A sandy bottom is made up of tiny, gritty particles of rock
that are smaller than gravel but coarser than silt (gritty, up to
pea size).
- Gravel (0.1-2 inches)
--A gravel bottom is made up of stones ranging from tiny
quarter-inch pebbles to rocks of about 2 inches (fine gravel -
pea size to marble size; coarse gravel - marble to tennis ball
size).
- Cobbles (2-10 inches)
--Most rocks on this type of stream bottom are between 2 and
10 inches (between a tennis ball and a basketball).
- Boulders (greater than 10 inches)
--Most of the rocks on the bottom are greater than 10 inches
(between a basketball and a car in size).
- Bedrock
--is solid rock (or rocks bigger than a car).
Estimate the percentage of substrate types at your site.
Figure 4.14
A representation of a rocky-bottom stream becoming
embedded with sand and silt
As silt settles on the streambed, spaces between the rocks are
filled in and the stream becomes more embedded.
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- Embeddedness
is the extent to which rocks (gravel, cobbles, and boulders)
are sunken into the silt, sand, or mud of the stream bottom (Fig.
4.14). Generally, the more rocks are embedded, the less rock
surface or space between rocks is available as habitat for
aquatic macroinvertebrates and for fish spawning. Excessive silty
runoff from erosion can increase the embeddedness in a stream. To
estimate the embeddedness, observe the amount of silt or finer
sediments overlying, in between, and surrounding the rocks.
- Streambed stability
can provide additional clues to the amount of siltation in a
stream. When you walk in the stream, note whether your feet sink
significantly into sand or mud.
- Presence of logs or woody debris (not twigs and
leaves)
in stream can slow or divert water to provide important fish
habitat such as pools and hiding places. Mark the box that
describes the general amount of woody debris in the stream.
- Naturally occurring organic material in stream.
This material includes leaves and twigs. Mark the box that
describes the general amount of organic matter in the stream.
- Water appearance
can be a physical indicator of water pollution.
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- Clear
- colorless, transparent
- Milky
- cloudy-white or grey, not transparent; might be natural or
due to pollution
- Foamy
- might be natural or due to pollution, generally detergents
or nutrients (foam that is several inches high and does not brush
apart easily is generally due to some sort of pollution)
- Turbid
- cloudy brown due to suspended silt or organic material
- Dark brown
- might indicate that acids are being released into the stream
due to decaying plants
- Oily sheen
- multicolored reflection might indicate oil floating in the
stream, although some sheens are natural
- Orange
- might indicate acid drainage
- Green
- might indicate excess nutrients being released into the
stream
-
Water odor can be a physical indicator of water pollution
-
- No smell or a natural odor
- Sewage
- might indicate the release of human waste material
- Chlorine
- might indicate over-chlorinated sewage treatment/water
treatment plant or swimming pool discharges
- Fishy
- might indicate the presence of excessive algal growth or
dead fish
- Rotten eggs
- might indicate sewage pollution (the presence of methane
from anaerobic conditions)
- Water temperature
can be particularly important for determining the suitability
of the stream as aquatic habitat for some species of fish and
macroinvertebrates that have distinct temperature requirements.
Temperature also has a direct effect on the amount of dissolved
oxygen available to the aquatic organisms. Measure temperature by
submerging a thermometer for at least 2 minutes in a typical
stream run. Repeat once and average the results.
Stream Bank and Channel Characteristics
- Depth of runs and pools
should be determined by estimating the vertical distance from
the surface to the stream bottom at a representative depth at
each of the two habitats.
- The width of the stream channel
can be determined by estimating the width of the streambed
that is covered by water from bank to bank. If it varies widely,
estimate an average width.
- Stream velocity
can have a direct influence on the health, variety, and
abundance of aquatic communities. If water flows too quickly,
insects might be unable to maintain their hold on rocks and
vegetation and be washed downstream; if water flows too slowly,
it might provide insufficient aeration for species needing high
levels of dissolved oxygen. Stream velocity can be affected by
dams, channelization, terrain, runoff, and other factors. To
measure stream velocity, mark off a 20-foot section of stream run
and measure the time it takes a stick, leaf, or other floating
biodegradable object to float the 20 feet. Repeat 5 times and
pick the average time. Divide the distance (20 feet) by the
average time (seconds) to determine the velocity in feet per
second. (See Chapter 5, Section 1 on flow for a more in-depth
discussion on using floats to estimate velocity.)
- The shape of the stream bank, the extent of artificial
modifications, and the shape of the stream channel
are determined by standing at the downstream end of the
25-yard section and looking upstream.
- The shape of the stream bank
(Fig. 4.15) may include.
-
-
Figure 4.15
Types of streambank shapes
Undercut banks provide good cover for fish and
macroinvertebrates.
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- Vertical or undercut bank
- a bank that rises vertically or overhangs the stream. This
type of bank generally provides good cover for macroinvertebrates
and fish and is resistant to erosion. However, if seriously
undercut, it might be vulnerable to collapse.
- Steeply sloping
- a bank that slopes at more than a 30 degree angle. This type
of bank is very vulnerable to erosion.
- Gradual sloping
- a bank that has a slope of 30 degrees or less. Although this
type of stream bank is highly resistant to erosion, it does not
provide much streamside cover.
- Artificial bank modifications
include all structural changes to the stream bank such as
riprap (broken rock, cobbles, or boulders placed on earth
surfaces such as the face of a dam or the bank of a stream, for
protection against the action of the water) and bulkheads.
Determine the approximate percentage of each bank (both the left
and right) that is artificially covered by the placement of
rocks, wood, or concrete.
- The shape of the stream channel
can be described as narrow (less than 6 feet wide from bank to
bank), wide (more than 6 feet from bank to bank), shallow (less
than 3 feet deep from the stream substrate to the top of the
banks) or deep (more than 3 feet from the stream substrate to the
top of the banks). Choose the category that best describes the
channel.
-
-
Narrow, deep
-
Narrow, shallow
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Wide, deep
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Wide, shallow
- Streamside cover
information helps determine the quality and extent of the
stream's riparian zone. This information is important at the
stream bank itself and for a distance away from the stream bank.
For example, trees, bushes, and tall grass can contribute shade
and cover for fish and wildlife and can provide the stream with
needed organic material such as leaves and twigs. Lawns indicate
that the stream's riparian zone has been altered, that
pesticides and grass clippings are a possible problem, and that
little habitat and shading are available. Bare soil and pavement
might indicate problems with erosion and runoff. Looking
upstream, provide an estimate of the percentage of the stream
bank (left and right stream banks) covered by the following:
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- Trees
- Bushes, shrubs
- conifers or deciduous bushes less than 15 feet high
- Tall grass, ferns, etc.
- includes tall natural grasses, ferns, vines, and mosses
- Lawn
- cultivated and maintained short grass
- Boulders
- rocks larger than 10 inches
- Gravel/cobbles/sand
- rocks smaller than 10 inches; sand
- Bare soil
- Pavement, structure
- any man-made structures or paved areas, including paths,
roads, bridges, houses, etc.
- Stream shading
is a measurement of the extent to which the stream itself is
overhung and shaded by the cover identified in 14 above. This
shade (or overhead canopy) provides several important functions
in the stream habitat. It cools the water; offers habitat,
protection, and refuge for aquatic organisms; and provides a
direct source of beneficial organic matter and insects to the
stream. Determine the extent that vegetation shades the stream at
the site.
- General conditions of the stream bank and stream channel,
and other conditions
that might be affecting the stream are determined by standing
at the downstream end of the 25-yard site and looking upstream.
Provide observations for the right and left banks of the
stream.
- Stream bank conditions
that might be affecting the stream.
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- Natural plant cover degraded
--note whether streamside vegetation is trampled or missing or
has been replaced by landscaping, cultivation, or pavement.
(These conditions could lead to erosion.)
- Banks collapsed/eroded
--note whether banks or parts of banks have been washed away
or worn down. (These conditions could limit habitats in the
area.)
- Garbage/junk adjacent to the stream
--note the presence of litter, tires, appliances, car bodies,
shopping carts, and garbage dumps.
- Foam or sheen on bank
--note whether there is foam or an oily sheen on the stream
bank. Sheen may indicate an oil spill or leak, and foam may
indicate the presence of detergent.
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Stream channel conditions that might be affecting the
stream.
-
- Mud/silt/sand on bottom/entering stream
--can interfere with the ability of fish to sight potential
prey. It can clog fish gills and smother fish eggs in spawning
areas in the stream bottom. It can be an indication of poor
construction practices, urban area runoff, silviculture
(forestry-related activities), or agriculture in the watershed.
It can also be a normal condition, especially in a slow-moving,
muddy-bottom stream.
- Garbage or junk in stream
--note the presence of litter, tires, appliances, car bodies,
shopping carts, and garbage.
- Other general conditions
that might be affecting the stream.
-
- Yard waste
(e.g., grass clippings)--is there evidence that grass
clippings, cut branches, and other types of yard waste have been
dumped into the stream?
- Livestock in or with unrestricted access to stream
--are livestock present, or is there an obvious path that
livestock use to get to the water from adjacent fields? Is there
streamside degradation caused by livestock?
- Actively discharging pipes are there pipes
--with visible openings discharging fluids or water into the
stream? Note such pipes even though you may not be able to tell
where they come from or what they are discharging.
- Other pipes
--are there pipes near or entering the stream? Note such pipes
even if you cannot find an opening or see matter being
discharged.
- Ditches
--are there ditches, draining the surrounding land and leading
into the stream?
Local watershed characteristics
- Adjacent land uses
can potentially have a great impact on the quality and state
of the stream and riparian areas. Determine the land uses, based
on your own judgment of the activities in the watershed
surrounding your site within a quarter of a mile. Enter a
"1" if a land use is present and a "2" if it
is clearly having a negative impact on the stream.
Visual biological survey
-
Are fish present in the stream? Fish can indicate
that the stream is of sufficient quality for other organisms.
- Barriers to the movement of fish
in the stream are obstructions that would keep fish from
moving freely upstream or downstream.
- Aquatic plants
provide food and cover for aquatic organisms. Plants also
might provide very general indications of stream quality. For
example, streams that are overgrown with plants could be over
enriched by nutrients. Streams devoid of plants could be affected
by extreme acidity or toxic pollutants. Aquatic plants may also
be an indicator of stream velocity because plants cannot take
root in fast-flowing streams.
- Algae
are simple plants that do not grow true roots, stems, or
leaves and that mainly live in water, providing food for the food
chain. Algae may grow on rocks, twigs, or other submerged
materials, or float on the surface of the water. It naturally
occurs in green and brown colors. Excessive algal growth may
indicate excessive nutrients (organic matter or a pollutant such
as fertilizer) in the stream.
Step 4 Complete all the field data sheets
After you have completed macroinvertebrate sampling, analysis
of findings, and the habitat characterization, make sure you have
completed the field data sheet to the extent possible and that
the recorded data are legible. If you are not able to determine
how to answer a question on the field data sheet, just leave the
space blank. Return all completed forms to your program
coordinator.
Streamside
Biosurvey: Macroinvertebrates (PDF, 28.7 KB)
Streamside
Biosurvey: Habitat Walk (PDF, 22.3 KB)
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