Benthic
Macro-invertebrate Sampling and Identification
- Set up monitoring equipment and take initial “vital
signs” of Rhoads Pond and Mill Creek.
- Teams of 6 students will be divided up along the
different responsibilities required.
- 2 students will be Data Collectors and deploy
Leaf Packs.
- 2 students will map the sites and collect GIS
data.
- 2 students will be Macro-invertebrate Samplers.
- Teams will visit either Phoads Pond or Mill Creek,
complete the initial sampling, map the site, deploy
Leaf Packs, and gather site data.
Benthic
sampling protocol
Aquatic insects are adapted to avoiding predation in
their environment. As a result, if we want to catch
aquatic insects, we need to minimize disturbance to
their micro-habitat prior to sampling. This means we
students should approach stream sampling sites from
downstream and avoid tromping in sampling areas. Sampling
streams with a D-net requires two people working together.
Transferring samples from net into zip-lock bags also
works best with two people.
Protocol --Stream sampling
1. Approach the sampling site from downstream, minimizing
splashing.
2. Take any depth measurement you might need at sample
site.
3. Label ziplock bag with site identifying information.
4. Person 1: Place D-net on stream bed with opening
facing upstream and net firmly pressing into stream
bottom. Tilt net slightly back to permit access of net
opening by person 2.
5. Person 2: Disturb rocks in front of the net
to dislodge stream insects and encourage flow of dislodged
insects into the net. Steam insects have evolved to
hanging on to substrate in fast moving water. For small
streams like Mill Creek the best way to do this is:
• Use your hand or a rock to disturb the stream
bottom in front of the net opening.
• Swirl water towards the net opening
• Pick up the surface layer of rocks in square
area in front of the net opening for a distance upstream
approx. equivalent to width of net.
• One by one scrub the surface of each rock with
your hands to dislodge clinging insect larvae.
• Set aside each rock after scrubbing.
• Disturb sediment in lower rock layer, swirl
water/bugs into net.
• Scoop net upwards so as it prevent insects
from escaping.
• Invert contents of net into ziplock bag (preferably
over a bucket or sieve/tray). Check net to make sure
there are no stragglers.
• Add enough water to cover contents of sample
(so that they survive the trip back to the lab)
Protocol --Pond sampling
1. Minimize splashing/disturbing the sampling site.
2. Take any depth measurement you might need at sample
site.
3. Label ziplock bag with site identifying information.
4 Use D-net to scoop across the pond bottom, removing
an area of sediment equivalent to width of net base
squared. The majority of larvae we are interested in
capturing will occur in the top layer of sediment so
try to capture the top inch of sediment as you scoop.
5. Move the net to buckets of pond water and rinse
contents by dipping the net bag into the water.
MAKE SURE TO KEEP NET OPENING ABOVE WATER WHILE YOU
DO THIS.
? Try to rinse as much of the fine
sediment from the net as possible, this will make sorting
in the lab easier.
6. Invert contents of net into ziplock bag (preferably
over a bucket or sieve/tray). Check the net to
make sure there are no stragglers.
7. If your gallon ziplock is less than 1/3 full of
sediment you should scoop more. More than ½ full
is probably overdoing it.
8. Add enough water to cover contents of sample (so
that they survive the trip back to the lab)
Both stream and pond samples ziplocks should
be placed in buckets, transported back to lab and kept
cool, preferably refrigerated until after-lunch viewing.
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