Benthic Field Study


22 févr. 2014 (il y a 7 années et 4 mois)

275 vue(s)

Benthic Field Study

Taken from Citizen’s Environment Watch



Benthic macroinvertebrates are widely
used to monitor environmental quality in

They are animals found on the bottom of
a waterbody that are large enough to be
seen with the naked eye, and lack a
backbone and internal skeleton.

They are relatively sedentary and
widespread with varying tolerances to
changes in water and sediment quality.

When to Sample

Sampling is possible anytime beginning in
early spring (Apr.) and ending in late fall

The most important consideration relates
to safety, where periods of high flow
associated with spring floods and storm
events should be avoided.

Where to Sample

The choice of where to sample will also be limited by health and
safety considerations.

Choose sampling sites where water conditions do not pose any
known or potential risks (e.g. pollution, high water levels).
Otherwise, the choice of a sampling site will largely depend on
the monitoring goals of each group. For example, some
community groups may be concerned with fish populations and
may wish to assess the effects of habitat loss due to

Construction sites are one possible source of increased
sedimentation. In this case, a sampling site should include both
a reference site upstream and a site downstream of
construction site. A similar approach would be used for any
suspected negative impact on stream quality (e.g. stormwater
outfalls, major roads).

Collecting Your Sample

Begin sampling at your downstream limit (
first transect) and at a point
as close to the bank as possible.

Place the net firmly against the stream bottom, making sure that no
macroinvertebrates can pass beneath the net.

Hold the net so that the current is flowing into the net.

Scoop up a continuous sample in a straight line across your transect. You
will need to keep emptying your sample into a filtering device as you

Pick up unembedded rocks along the transect and carefully rub their
surface to dislodge any attached bugs and collect them in the net.

Place sample into a white tray for sorting

Avoid entering the stream prior to sampling. Any additional sampling (e.g.
biological, chemical) or site survey should be carried out after the
macroinvertebrate sampling has been completed.

Sort your sample

Carefully disturb the contents of the tray and look
for moving and resting water bugs.

Look carefully for smaller bugs (<3mm) and
under/on the surface of remaining small debris,
twigs, small rocks, etc.

Be sure not to pick only the largest and/or least
mobile macroinvertebrates.

As a rule, once a bug is spotted, it must be picked,
regardless of size or movement.

Use magnifying glasses and your identification
chart to identify your sample. When a
macroinvertebrate is discovered place a line on
your data collection sheet.

Sketch your site

This should
be completed
for each of
your transects
on the sheet

Make it to

You are
welcome to
use symbols

Final Notes

We are going to complete three data
collections (transects)

Upstream, midstream and downstream

From each data source (transect) collect a
raw sample to bring back in a sample bag.

Complete your package and hand it in.