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 Deckers Creek. 

 

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)