VA SOS Modified Method
The
Modified Virginia SOS Method
When you understand the steps outlined below, you can follow the links
to finish the monitoring session!
The method
below is suited for Virginia's rocky bottomed streams. If your stream has a muddy bottom (lower Piedmont
and coastal plain), please go to the Eastern Muddy Bottom Method for
details.
1. Collecting the Macroinvertebrates
Select a riffle typical of the stream; a shallow, fast-moving area with
a depth of 3 to 12 inches (8 to 30 cm) and stones that are cobble-sized
(2 – 12 inches) or larger. Stone size is important, as the macroinvertebrates
surveyed prefer these stones for protection, nutrients, and oxygen. Place
the kick seine perpendicular to the flow of water immediately downstream
of the 1x1 foot area in the riffle
you
have chosen. The bottom, weighted edge of the net should fit tightly against
the stream bottom. You may wish to use cleaned rocks from outside your
sampling area to hold the net firmly to the bottom. This will prevent
insects from escaping under the net. Tilt the net back so the water flowing
through it covers a large portion of the net. Be careful not to tilt the
net so much that water flows over the top, allowing organisms to escape.
2.
Quickly sample the targeted area for 20 seconds. To sample, lift and rub underwater all largerocks in the sample area to
dislodge any clinging organisms. Rub all exposed surfaces of rocks in
the sampling area that are too large to lift. Dig around in the small
rocks and sediments on the streambed in order to dislodge any burrowing
macroinvertebrates. After sampling for 20 seconds, carefully rub off any
rocks used to anchor the net. Then remove the seine with an upstream scooping
motion to keep all the macroinvertebrates in the net.
3.
Processing Your Sample
Place the net on a flat, light colored surface, such as a white sheet,
table, or piece of plastic. This makes the organisms easier to see. Using
tweezers or your fingers, gently pick all the macroinvertebrates from
the net and place them in your collecting container. Carefully check both
sides of any debris in the sample, as insects will cling to any available
litter. Any moving creature is considered part of the sample. Look closely
for very small organisms. It is important to thoroughly pick all organisms
from the net. Once you have sorted them off the net, lift it and examine
the underlying area. Collect any organisms that have crawled through the
net. Again, it is important to collect all these organisms for an accurate
sample.
Once all
the macroinvertebrates are removed from the seine, count the number of
organisms in the
sample.
If at least 200 organisms have not been sampled, another net must be collected
from a different area in the same riffle. The organisms from the second
net will be added to the first. The length of sampling time can be adjusted
depending on the number of organisms collected in the first, with the
maximum sampling time per net being 90 seconds. The second net and area
beneath are again sorted in their entirety. Again the organisms are counted,
and a third net will be collected if 200 organisms have not been obtained.
This process is repeated until at least 200 organisms are found or 4 nets
are collected, whichever is first. Each net collected must be sorted in
its entirety, even if that leads to a sample of well over 200 organisms
Once at least 200 organisms have been obtained, separate them into look-alike groups. Use body shape and number of legs and tails, since the same family or order can vary considerably in size and color. Use the tally sheet and macroinvertebrate key to aid in identification. Record the number of individuals found in each taxonomic group on the tally sheet. Include the total number of organisms in the sample on the lower right corner of the tally sheet. Follow the tables attached to the tally sheet to calculate the individual metrics and the final ecological condition score.
Practice
calculating individual metric and final ecological condition scores by
using our example data. See sidebar for link to practice calculations.
Be sure you have completely filled out the first page of your form and
have completed a habitat assessment. See sidebar for link to habitat assessment
information.
Please turn in your data to the VA SOS Program within two weeks of sampling. See sidebar for information about submitting your data to VA SOS.