US Long-Term Ecological Research Network

Sample Jars
Label 4-oz jars with computer printed labels for Wisconsin net and HP samples. Add the date to the label using a soft pencil. Cover the labels with a strip of clear contact paper, making sure the contact paper completely covers the label and encircles the jar. Cap and organize the field collection jars.
Weigh the empty zooplankton jars, including lids, on the Mettler XS603S balance. Record these weights on the ‘Volume by Weight’ data sheet.
Add 80 ml 95%EtOH to the field collection and Wisconsin net zooplankton jars; leave the HP jar empty. Add 2 ml Lugols iodine solution to the phytoplankton bottles. Keep the zooplankton jars cold until sample collection.

Chlorophyll filters
Load filter holders with glass fiber filters. The filter should be placed so that the ‘fuzzy’ side faces the input end of the filter holder. Tighten the filter holders gently to avoid tearing the filters.

Pack the zooplankton cooler with: Schindler and Wisconsin net sample jars, wash bottle with 95% EtOH, Schindler trap parts (net, ring clamp, cup, pin, spare pin), thermometer, wind meter, pencils, screwdriver, ice pack.
In the chlorophyll cooler place: loaded filter holders enough for sample depths plus one blind plus two spares, phytoplankton sample jars, ice pack.


  • clipboard, data sheet, no.1 pencils, watch
  • peristaltic pump and cable to power pump, 12 volt battery
  • ¼” ID tygon tubing with weight for chlorophyll collection
  • 3/8” ID tygon tubing with weight for phyto collection
  • zooplankton and chlorophyll coolers
  • graduated cylinders (1000, 2000 ml), ring stand, pressure gauge
  • light meter data logger, deck and depth sensors
  • Schindler Patalas trap
  • Wisconsin net with cup
  • metered line, Secchi disk, Secchi viewer
  • oars, cushions and vests, motor, gas
  • [Additional winter gear: ice depth stick, tent, heater, auger, spud, spoons, shovel, matches]

Record the lake, station, date, observers, anchor used, on-station time, and equipment information on the data sheet. Complete the weather information section, and record the staff gauge reading.

Light profile
The light profile is taken first. The other samples to be collected by the bio crew member either disturb the bottom sediments, which should not be done until the bottom chem samples have been collected, or cannot be collected before the thermal profile has been determined by the chem crew member.
Place deck sensor so that it is level and nothing casts a shadow over it. Lower the depth rig on the sunny side of the boat holding the rig away from the side of the boat. This keeps the boat’s shadow from affecting the readings. When lowering the depth rig, the weight of the rig should be supported by the metered line rather than the sensor cable. Beginning at the surface, take light readings down through the water column until there is no measurable light. On Big Muskellunge, Crystal, Sparkling, and Trout take readings every meter. On Allequash take readings every half meter. On 12-15 Bog and 27-2 Bog take readings every quarter meter.

IMPORTANT! The metered line is labeled so that the first red mark is 3 meters from the clip. Subsequent red marks are five meters apart. The first red mark equals 5 meters only with the 2 meter long Schindler trap. For the light rig which is one meter from sensor to clip, the first red mark is at 4m. For the Wisconsin Net and Secchi disk, the first red mark is at 3m.

Schindler Patalas samples
Collect samples from the target depths at the deep sampling station in each lake. Sample depths are measured from the middle of the trap, so that the actual sample depth range is from one meter above to one meter below the target value. For example, a target depth of 5 meters results in a sample spanning from 4 meters to 6 meters. On the data sheet record the sample depths actually collected.

Target Depths:
TR: 1, 3, 5, 7, 9, 15, 20, 27, 31 meters
CR/BM: 1, 3, 5, 7, 9, 11, 13, 15, 18 meters
SP: 1, 3, 5, 7, 9, 11, 13, 15, 17 meters
AL/TB: 1, 3, 6 meters
CB: 1 meter
Take samples starting at the surface and going down. Lower the trap slowly so that it remains vertical in the water. Pause at the target depth long enough to allow both trap doors to close completely, and check when it reaches the surface that both did close.
Drain the trap through the net and cup, swirling the cup until the liquid level is below the mesh windows. Remove pin to drain the sample into jar. Rinse cup and pin several times with EtOH into the sample jar. Do not fill sample jars above the 50 ml mark.
Do not take the bottom sample until the chem crew member is done collecting chemistry samples from the bottom depth.

Phytoplankton samples
Phytoplankton samples are collected six times per year, on the four quarterly dates plus the June and July chemistry sampling dates.
Determine the phytoplankton strata and sample volumes, and record on the data sheet. During stratification collect samples from the epilimnion, metalimnion, and hypolimnion as determined by the temperature profile. During mixis divide the lake into strata of equal depth, three strata for the deep lakes and two for the shallow lakes. Use the table on the clipboard cover to determine the volume of water contained within the tubing for each stratum.
Lower the sample tubing slowly to the bottom sample depth so that it fills evenly. The top of the tubing should be open and not connected to the pump to allow proper filling. Connect tubing to pump, and pump out the volume of water representing the epilimnion into a graduated cylinder. Mix the sample by covering the cylinder with your hand and inverting it, and fill the sample jar. Repeat for the metalimnion and hypolimnion samples.
If a stratum is less than three meters deep, there is not enough volume of water in the tubing for a sample. Lower the tubing additional times to collect enough water to fill the sample jar. A two meter stratum will require two ‘dips’ while a one meter stratum will require three dips. Take an equal amount from each subsample to make up the phyto sample.

Chlorophyll samples
Chlorophyll samples are collected at specified depths on each lake, three to eight depths depending on the depth of the lake. Collect samples from the bottom depth first. Lower the tubing to the bottom sample depth, and pump an entire tubing volume out of the tubing and discard. This clears the tubing, filling it with water from the desired sample depth. Attach the pressure gauge and filter to the pump outlet tubing so that the flow of water passes through the gauge before going through the filter. Pump water through a filter until the pressure gauge reads 15 psi or until 3000 ml have been pumped through the filter, whichever comes first. At pressures greater than 15 psi some phytoplankton cells are broken, and chlorophyll is washed through the filter instead of being retained on it. Remove the filter, reverse it, and use the pump to suck excess water from the filter holder. Immediately place the filter in a cooler to keep it cold and dark until returning to the lab. Record the filter holder letter, volume filtered, and maximum psi on the data sheet.
Raise the tubing to the next chlorophyll depth. The tubing is now at the proper depth, but is still filled with water from the previous depth. Again, clear the tubing by pumping an entire tubing volume out of the tubing to discard. Note that if you are clearing at 12 or 15 meters but have a total tubing length of 20 meters, you must clear out the entire 20 meter volume of water from the tubing. The tubing must be cleared at each depth before collecting the chlorophyll sample.
Collect a duplicate chlorophyll sample from the same depth as the chemistry sample blind.

Wisconsin Net samples
Lower the Wisconsin net to the bottom sample depth. Pull it up slowly at a rate of about 3 seconds per meter. A slow haul prevents the net from pushing water and plankton away from the mouth of the net. Drain the cup through the mesh windows until the water level is below the lower window, then pour contents into the sample jar. Rinse the inside of the cup with EtOH several times adding the rinse to the sample jar. Wait until the chemistry crew member is finished taking samples from the bottom depth before taking the Wisconsin net sample.

Secchi Disk
Lower the Secchi into the water on the shady side of the boat. Lower the disk until you cannot see it; record the depth as the ‘down’ reading. Raise the disk until you can again see it; record the depth as the ‘up’ reading. Repeat Secchi disk depth measurements while looking through the PVC pipe Secchi disk viewer. Looking through the viewer reduces the effects of glare and waves on the measurements. The plexiglas window at the bottom of the viewer should be just under the surface of the water. For winter sampling take only ‘no-viewer’ Secchi disk measurements.

Additional Winter Data
During ice cover, measure the ice thickness differentiating between ‘blue’ and ‘white’ ice. Also record the water level as the number of centimeters below the surface of the ice. Take ten measurements of snow depth from the area surrounding the sample site.

(reviewed 2/2012)


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