We will use the following procedure to determine the water quality of a site.
- Generate a water profile using the YSI.
- Take your GPS position.
- Collect nutrient and chlorophyll samples.
- Take the Secchi Depth.
- Process the Chlorophyll-A from the field.
Materials List for all Water Quality Monitoring (Materials for Benthic Sampling)
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Thanks to Jill Elenbaas, Emily Scott, and Sarah Mountcastle for their help preparing this material.
Generate a water profile using the YSI 600R Sonde
Materials
YSI 600R Sonde- Sonde Cables
- YSI Handheld Computer
Method
- Plug the Sonde into the handheld computer and attach line to the sonde.
- Submerge the probe in the water and wait for the readings to stabilize. Take the first reading as close to the surface as possible without allowing the instrument to come out of the water. Record as your surface reading.
- Lower 1 meter into the water and repeat measurements.
Repeat at one meter increments, all of the way to the bottom.- Near the bottom, carefully lower insturment until it is about 0.2 meters from the bottom. Taking a sample at the actual bottom risks damaging the Sonde and will give false readings. Record your readings.
- When you get back, do the post-test calibration to make sure the measurements were accurate.
- When you are finished with your tests and with post-test calibration, be sure to rinse the Sonde off. Salt water will corrode the metal, and harm the measuring instruments. They can be easily washed off by spraying some fresh water on the instrument. Be careful to spray off the entire instrument.
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Take your GPS position. (Two Types of GPS)
The Global Positioning System (GPS) consists of 24 geo-synchronous satellites. These satellites broadcast a semi-random code constantly. GPS receiver units can take the codes from the visible satelites and triangulate your location on the earth. With some correction for atmospheric conditions, these measurements can be hyper-accurate. Some measures can be corrected and made accurate down to the nearest centimeter.
Needless to say, this is a very useful tool to geologists. It allows you to accurately locate where samples are taken from, where different studies are taking place, and so on.
We use two different GPS systems. The first is GeoExplorer. This is the large handheld unit. The Pocket Trimbles are the palm pilot version of GPS. This program is run through the ArcPad program, so it will be helpful to have some background in using GIS programs.
Both systems load data easily into ArcMap or ArcView. Below are instructions for both of the systems.
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Collecting Water Bottle Samples for Nutrients and Chlorophyll-A
Materials
- YSI Readings
- Water Bottle Sampler
- Cooler
- Ice
- Nutrient Syringe
- Filter
- Nutrient bottles
- Chloroform
Method
- Use YSI to determine a profile of the water temperature.
- From your measurements, determine the location of the thermocline layer. The thermocline layer is the point at which the water rapidly changes temperature from warm surface water to colder water.
At the surface, Put some of the water from the sample site in a bottle, swish it around, and pour it out. Repeat twice. After rinsing, do not put your fingers inside of the bottle. When rinsing, have the cap of the bottle on.- Fill clear bottle with water from the sample site.
- Take nutrient sampler syringe, fill with water from the bottle, swish, and pour out. Repeat twice.
- Fill syringe with water from the bottle, place the filter on the syringe.
- Fill nutrient bottle 3/4 full with water from the syringe, place two drops of Chloroform in it.
- Cap and record the bottle number.
Pour remaining water into amber bottle for Chlorophyll-A sample.- Set up the water bottle sampler by lifting the plungers and attaching the wires to their holders.
- Lower water bottle to the desired depth.
- Drop weight when at desired depth "tripping" the bottle. This will trap the water from that depth only.
With the sample, rinse out the bottles. Pour a little water into the bottles, swish, and pour out.- Pour the remaining water into the designated amber bottle.
- Take a nutrient sample as done above.
- Take nutrient sampler syringe, fill with water from the bottle, swish, and pour out. Repeat twice.
- Fill syringe with water from the bottle, place the filter on the syringe.
- Fill nutrient bottle 3/4 full with water from the syringe, place two drops of Chloroform in it.
- Cap and record the bottle number.
- Label with location, date, your initials, and cap the bottle.
- Repeat for the bottom, above the thermocline, and below the thermocline.
- To determine bottom depth, use depth measurements from YSI to lower to near the bottom and collect from approximately .3 to .5 meters from the bottom. Collecting at the bottom or hitting the bottom will give false readings
Store sample bottles in cooler with ice.- When you get back you will need to process the Chlorophyll-A samples.
- Place the Nutrient Samples in the freezer.
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Taking the Secchi Depth
Overview
Secchi depth measurements allow you to be able to compare to water visibility and the turbidity in the water to previous records. A secchi disk is a small disk with an alternating color pattern that is lowered into the water to determine water clarity.
Image courtesy of the Lake George Association.
Materials
- Secchi Disk
- Marked Rope
Method
To take the Secchi Depth, lower the Secchi Disk into the water until it is not visible. Then pull it up to where it is just barely visible. Slowly raise and lower the disk at this point to find the lowest possible depth at which it is visible. Read and record the measure on the line.
Image courtesy of Chicago Area Paddling/Fishing Riverwatch.
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Process the Chlorophyll-A from the field. (Filtering Chlorophyll-A)
As chlorophyll-a is light sensitive, you will need to do this in the lab and turn off or block as much light as you can. This includes turning off the room lights and at least partially closing the blinds.
Do not suck fluid through the pump. It will damage the pump. Make sure any water flows away from the opening to the vacuum and that the flask does not fill up completely.
Materials
- Pump
- Graduated Cylinder
- Filter Paper
- Water Sample
- Flask with pump attachment
- Forceps
- Pipette
- Aluminum Foil
- Paper Towel
- Ziploc Bag
- Pen
- Label
Method
- Clean out graduated cylinder with sample three times.
- Gently turn bottle upside down to mix the water evenly. This is important as the plankton will naturally settle down to the bottom of the bottle.
- Pour 100mL of your sample into a graduated cylinder. Keep the remainder in case an accident necessitates repeating the experiment. It may be necessary to use a smaller amount of the sample because of the concentration of the sample. If it is apparent that the sample is very thick, use only a 50mL sample.
- Attach pump to the graduated flask. Make sure that the hose is on the vacuum side of the pump.
- Place stopper with filter holder in graduated flask.
- Use the forceps to pick up the filter paper.
- Place the concave side up on top of the Filter Holder.
Clean pipette three times.- Place pipette on top of filter paper.
- Clip pipette to filter holder.
- Fill pipette with water.
- Turn on pump.
- If pumping thick fluid, do not exceed "5" on the inner dial of the pump. You can reduce the pressure on the pump by turning the knob on the right hand side of the pump. This will release some of the vacuum pressure and reduce some of the pressure on the pump. However, do not let the pressure get so low as to not be drawing water through the filter.
- As the water level lowers in the pipette, add more water.
Do not allow the filter to fully dry. Get most of the water out, but do not suck it dry. This will alter the cells you have filtered, altering the result.- Pull out a small piece of tin foil. Place a piece of paper towel onto the foil.
- With the forceps, gently lift the filter off of the filter holder, holding only the outside of the filter paper. Do not touch the center of the filter, and be careful not to tear it.
Place the filter on the paper towel, filtered side up, and fold in half with the forceps. Be sure it is folded in half, otherwise some of the sample will be transferred onto the paper towel.- Wrap the paper towel around the filter, and the foil around the paper towel.
- Label with date, location, depth, "Chlorophyll-A," amount filtered, and your initials and place in Ziploc bag.
- Place in freezer.
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