Accokeek Creek is a tidal tributary of Potomac Creek, which
runs into the Potomac River within sight of Washington DC. The site
Cacapon Institute sampled for this activity is on The Alice Ferguson
Foundation's Hard Bargain Farm. According to Maryland DNR, the watershed area of
Accokeek Creek at this site is about 3.3 square miles, with 7.6% of the
watershed urban, 5.7% farm, and 86.6% is forested.
Courses at
AFF Hard Bargain
Farm immerse students in various field studies involving fun and innovative
hands-on activities and field investigations designed to engage all learning
styles. Their programs for elementary to middle school students are
designed to promote understanding and stewardship of the natural resources in
the Potomac River watershed and the legacy of farming in America. Many students,
teachers and environmental education practitioners from Maryland and Washington
DC have sampled the same area of Accokeek Creek you just sampled virtually.
If you used the other activities in the
Benthic Macroinvertebrate Portal prior to using this activity, you
should have a good understanding of everything you did in A
Virtual Stream Sampler. If you haven't used those
activities, we suggest you run through the Introduction to
Stream Sampling to get the basics.
Click here to see a
summary of the BMIs you picked in Accokeek Creek and to see a
picture of the BMI "take" that was collected in Accokeek Creek by CI
staff.
Your Score
The benthic macroinvertebrate section is worth
50% of the total score, the other two sections are each worth 25% of
final score.
- In the benthic macroinvertebrate section,
if there are 15 organisms, then finding everything in the net is
worth 15 points, and correctly identifying everything is worth
15 points, for a total of 30 points (100%). You are
penalized heavily if you guess at answers on the list and
get them wrong. Every wrong guess is a point off.
Since you have three chances to guess at the answer for each
organism before you are forced to use the dichotomous key, with
15 organisms that would be 45 points off. Yes, you can get
a very negative score. So, if you don't know what
something is, don't guess - use the key. Guessing in
the key is not penalized.
-
The habitat section has a maximum
score of 5. Each wrong answer counts off one. Each
question you don't try to answer counts off two. So you
are better off guessing and being wrong than not answering at
all. If you don't guess on anything you can get a
negative 100% score in this section. Ouch!
-
The water quality section has a
maximum score of 6. Each wrong answer counts one off.
Each question you don't try to answer counts 2 off. So you
are better off guessing and being wrong than not answering at
all. If you don't guess on anything you can get a
negative 100% score in this section. Ouch!
-
Even though you can get negative
scores in each section, the worst total score you can get is
zero.
The Stream Score
Aquatic
organisms can be used as indicators of water quality. The advantage
of using aquatic organisms over chemical indicators - such as the
amount of a certain chemical in a water sample - is that animals are
constantly "sampling" their environment. The communities of
organisms found in benthic samples are indicative of water quality
conditions over time. Chemical measures, in contrast, provide a
momentary snapshot of conditions in a constantly changing
environment.
Many
years ago, the focus was on "indicator
species." An indicator species is one that, by its presence,
absence, or abundance relative to other organisms, indicates
environmental conditions. For example, the presence of numerous
non-biting midge (Chironomidae) larvae in a stream may indicate
severe organic pollution.
Over the years,
researchers generally moved away from the use of individual
indicator species and toward "metrics" that look at groups of
species. A typical metric might look at the total number of
different species or the relative abundance of different species.
For instance, if a researcher finds that species tolerant of
degraded water quality outnumber kinds that are intolerant of
pollution, it is more likely that degraded conditions exist But the
mere presence of pollution-tolerant organisms does not necessarily
equate to water quality problems, because these organisms are often
widely distributed.
A
Virtual Stream Sampler scores the stream using two popular
methods in use by volunteers in the Chesapeake Bay Watershed, the
West Virginia Save Our Streams Stream Score Index, and Virginia Save
Our Streams Stream Score. Both of these scores are based on a
suite (a group) of "metrics" that, when averaged together, are an
effective way to tell a stream's story. Two metrics are used
by both West Virginia and Virginia:
-
percent tolerant organisms tells you
what percentage of the organism in the sample are tolerant of
pollution, and
-
Virginia's percent
Mayflies, Stoneflies, and most Caddisflies is similar to West
Virginia's % EPT score. This score looks at what
percentage of the sample consist of theswe three groups of
insects that are mostly sensitive to pollution. Virginia's
score breaks out the pollution tolerant "common netspinner
caddisfly."
The two tables below
provide details on each system, and links for more information.
Virginia SOS Stream
Score |
Metric |
Your Metric Score |
Good (2) |
OK (1) |
Poor (0) |
% Mayflies, Stoneflies, and Most Caddisflies |
X% |
> 32.2 |
16.1 to 32.2 |
< 16.1 |
% Common Netspinner |
X% |
< 19.7 |
19.7 to 34.5 |
> 34.5 |
% Lunged Snail |
X% |
< 0.3 |
0.3 to 1.5 |
> 1.5 |
% Beetle |
X% |
> 6.4 |
3.2 to 6.4 |
< 3.2 |
% Tolerant Organisms |
X% |
< 46.7 |
46.7 to 61.5 |
> 61.5 |
% Non-Insect Organisms |
X% |
< 5.4 |
5.4 to 20.8 |
> 20.8 |
Get
details on how the Virginia Save Our Streams Score is calculated and
learn much more about the Virginia
program. |
Total # of 2s: |
Total # of 1s: |
Total # of 0s: |
N2 |
N1 |
N0 |
Multiply by 2: |
Multiply by 1: |
Multiply by 0: |
N2 x 2 = S2 |
N1 x 1 =S1 |
N0 x 0 = S0 |
Now add the 3 subtotals (S2 + S1 + S0) to get the Save Our Streams Multimetric Index
Score |
_____ Acceptable Conditions (9 to 12)
_____ Conditions cannot be Determined - Gray Area (8)
_____ Unacceptable Conditions (0 to 7)
|
West Virginia
SOS Stream Score |
Metrics |
What Values Mean |
Best Standard Value (BSV) |
Scores |
1. Total Taxa |
Higher is better |
22 |
Your Value/BSV x 100 |
2. EPT Taxa |
Higher is better |
13 |
Your Value/BSV x 100 |
3. Biotic Index |
Lower is better |
3 |
(10-Your Value)/7*100 |
4. % EPT Abundance |
Higher is better |
90 |
Your Value/BSV x 100 |
5. % Tolerant |
Lower is better |
2 |
(100-Your
Value)/(100-BSV)*100 |
6. %Dominance |
Lower is better |
20 |
(100-Your
Value)/(100-BSV)*100 |
Stream Score Index (SSI) |
Average of the above
scores |
Reading the WV SOS Stream Score table:
> 85 = Optimal,
85-70 = Suboptimal, 69-50 = Marginal, < 50 = Poor
|
The West
Virginia Save Our Streams Program has three levels of stream sampling
methods for volunteers to choose from. All of them require
training and volunteer certification by the state volunteer coordinator
for their data to be accepted. Level I requires the least
technical expertise, Level III the most. The Stream Score
above is a hybrid of the Level II and Level III scoring (we wanted to
add in percent Dominance), and similar to
the professional level West Virginia Stream Condition Index.
-
"Total Taxa" = how many kinds of BMIs were found. Higher
values are better, 22 would be a very good stream.
-
"EPT
Taxa" = how many kinds of Mayflies (Ephemeroptera), Stoneflies
(Plecoptera), and Caddisflies (Trichoptera) were found.
Higher values are better, 13 would be a very good stream.
-
"Biotic Index" = the Hilsenhoff Biotic Index, that multiplies
abundance of each organism by its sensitivity to pollution (ranked
from 1-most sensitive to 10 - least sensitive), and divides
the sum by the total number of organisms caught. Lower
values are better, 3 would be a very good stream.
-
"%
EPT Abundance" =
how
many Mayflies (Ephemeroptera), Stoneflies (Plecoptera),
and Caddisflies (Trichoptera) were found. Higher values
are better, 90 (out of a total of 200 organisms) would be a very
good stream.
-
"%
Tolerant" = the percentage of the total number of organisms that
were caught that are tolerant of pollution.
Lower
values are better, 2 would be a very good stream.
-
"%Dominance" = the percentage of the most abundant
organism in the sample out of the total number of organisms caught.
Lower
values are better, 20 would be a very good stream.
You can
learn much more about the West Virginia SOS program, and even
download spreadsheets for calculating your own stream scores.
|
The BMIs of Accokeek Creek |
Collected June 29, 2011 by N Gillies (Cacapon Institute) |
Sorted and identified 1/8 of total sample |
Caddisflies |
|
Common Netspinner |
143 |
Fingernet |
1 |
Humpless Casebuilder |
1 |
Stoneflies |
|
Common |
11 |
Mayflies |
|
Small Minnow |
3 |
Beetles |
|
Riffle, larva |
10 |
Riffle, Adult |
2 |
Dragonfly |
3 |
Crane Fly |
8 |
Chironomidae |
300 |
Watersnipe Fly |
4 |
Amphipods |
3 |
Crayfish |
2 |
Lepidoptera Larva – change to alderfly |
1 |
Roundworm |
1 |
You might like to try entering the above BMI data
into the Virginia or West Virginia spreadsheets to calculate the BMI
Index Score for yourself, or try it using other state's volunteer and
professional scoring methods.
Do they all give the same answer? If not, how do they differ?
|
|