Eastern Muddy Bottom Method

Great thanks to Dr. Chas Gowan at Randolph Macon College in Ashland for his expertise in developing this method!

The Virginia SOS Eastern Muddy Bottom Method
When you understand the steps outlined below, you can follow the links
to finish the monitoring session!

2. Collecting the Macroinvertebrates
Start your collection at the downstream limit of your 100-meter sampling area.  Move upstream as your collect your sample to avoid low visibility caused by sediment resuspension.  Collections are made in all velocity regimes and all available habitats in the assessment area.  Sampling of the channel bottom should be avoided as much as possible.A single jab consists of aggressively thrusting the net into the target habitat for a distance of approximately 1 meter; i.e. the distance the net can be swept while standing in one place.  This initial “jab” is followed by 2-3 sweeps of the same area to collect the dislodged organisms.  The jab is transferred to the sieve bucket (or other seining device) by banging the net over the bucket opening or by inverting the net into a partially submerged bucket.  Contents of the net are transferred into the sieve bucket after each jab. 

3. Sampling Techniques for Habitat areas Woody snags – snags or submerged woody debris, are sampled by jabbing in medium sized snag material (sticks and branches).  Large material (e.g., logs) may be sampling by scraping the net along the surface.  Woody debris may be picked up, held in the net, and rubbed by hand.  Banks – Stream banks with roots and snag material are sampled similar to snags.  Vegetated banks are preferred over unvegetated banks.  If the bank is undercut, be sure to jab back under the bank, drawing the net from the stream bottom to the top of the undercut bank.  Submerged aquatic vegetation – submerged macrophytes are sampled in deep water by drawing the net through the vegetation from the bottom to the surface of the water.  Macrophytes in shallow water are sampled by bumping the net along the bottom in the macrophyte bed.

3. Processing Your Sample
Empty the contents of your sieve bucket onto a flat, light colored surface, such as a white sheet, or table.  This makes the organisms easier to see.  Spread the sample across a square portion of your surface (as large an area as needed so that the material is not clumped into piles).  Using a stick as a guide, divide your sample into 4 grids to make 4 squares of the same size.  Randomly select one of these squares to start your picking and identification.  Using tweezers or your fingers, gently pick all the macroinvertebrates from selected grid and place them in your collecting container.  Any moving creature is considered a part of the sample.  Look closely for very small organisms and take your time.  It is important to thoroughly pick all the organisms from the grid.  Record the number of individuals you find in each taxonomic group on the tally sheet.  Our tally sheet and metric calculations should be based on a sample size of at least 100 organisms.  COUNT THE SCUDS FOUND IN YOUR SAMPLE BUT DO NOT COUNT THEM TOWARDS THE 100 ORGANISMS REQUIRED!  In other words you need at least 100 non-scud organisms for your sample.  If you did not pick 100 organisms from the grid.  You must select another grid to pick.  The second grid must be picked in its entirety.  Again, if 100 non scud organisms have not been tallied, count the subsequent grids in the entirety.

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.