Measuring
Displacement Volume
Supplies: rubber gloves, safety goggles, 2 1-liter graduated
cylinders, 2 smaller graduated cylinders (25 to 100 ml), 2 funnels: 1 wide-necked
open funnel and 1 small-necked one with mesh attached to the inside or a sieve
that fits inside the small-necked funnel, squeeze bottles (water and formalin
or other preservative), sieve of mesh
size equal to or smaller than that on sampling net.
Put on rubber gloves
Remove jars for 1 net from sample box (may be from one
to many jars for a single net sample)
Fill in the data sheet with MOC tow#, date, and
net# . jar#
Take first sample to hood. Put on safety goggles.
Remove lid and internal label with long forceps. Get
most of zooplankton off by dipping into jar and place label inside lid after
checking that internal label agrees with lid label.
Remove large (>5cc) animals (medusae, some fish or shrimp)
and measure their displacement volume in the small graduated cylinders:
-Note this volume on data sheet.
-Place small sieve in small funnel and set them on top
of second empty small grad graduated cylinder.
-Pour animal plus liquid into sieve and let drain.
-Note this volume on data sheet as well as the type of
animal.
-Return the specimen to the main sample.
Pour the large sample into the 1-liter graduated
cylinder using the open funnel on top (no mesh in funnel). Rinse sparingly the
jar, funnel and sides of the graduated cylinder. Diluting the sample with water
could cause it to rot. Add a little water with the squeeze bottle to bring the
level up to an even line on the graduated cylinder.
Note this volume on the data sheet (sample + liquid)
Place the large funnel containing the sieve or mesh on
top of the second, empty graduated cylinder.
Pour the sample into the empty grad. Don’t worry about
animals stuck to the sides of the first grad. Do not add any liquid to wash
sample into the second grad.
Swirl the funnel to remove excess liquid until most of
liquid is done dripping (about 1 minute, but varies sample to sample). Carefully
drawing the samples toward the center with large forceps is sometimes helpful.
Note this volume on data sheet (liquid vol.)
Rinse the graduated cylinder and the mesh-funnel into
the sieve with the hose and return most of the dry sample to the jar using the
open funnel.
Use water from faucet with hose to wash the sample on
sieve to one side and then use squirt bottle of water (sparingly) or the
preservative filled one to rinse the sample from sieve to jar.
Add enough of the filtered formalin to fill the jar,
dispose of remainder in appropriate waste container.
- Check the sample's pH and add buffer (sodium borate or borax) if ≤ 8.0.
- Replace cap, swirl if buffer of formalin was added,
and rinse outside of jar.
- Rinse everything well after each net sample.