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How to Measure Algae Growth

Algae is common in aquatic environments. It grows and reproduces in the photic zones of ponds and lakes. This zone is the upper part of a body of water where sunlight penetrates. Algae growth, or bloom, is accelerated by human activities. Too much phosphorus and nitrogen entering waterways causes excessive algae growth. This affects a lake's water clarity, or the amount of particles in the water. It is an indicator of ecosystem health. It is important to monitor algae growth to ensure that lakes and ponds remain healthy.

Things You'll Need

Opaque water sample bottles
Brown water sample bottles
Permanent marker
Plastic bags
Cooler
Secchi disk
Field sheet
Sample forms
Ice
Zip-close plastic bags
Tape
Strapping tape

Instructions

- 1
  Label opaque and brown water sample bottles using permanent ink with the lake name and the date. Place the sample bottles in plastic bags and place in a clean cooler for the trip.
- 2
  Attach a Secchi disk to a measured line marked off in meters (subdivided into tenths of a meter). This is a weighted circular disk 20 centimeters in diameter with four alternating black and white sections painted on its surface.
- 3
  Lower the disk into the water until you can't see it.
- 4
  Raise the disk until it reappears. The water level where the disk vanishes and reappears is the Secchi disk reading. Record the data on a field sheet
- 5
  Wash your hands with lake water before collecting water samples for chlorophyll a testing. Use the opaque water sample bottles. Remove the bottle cap and rinse the cap and bottle. Do not touch the inner surface or mouth of the bottle to avoid contamination.
- 6
  Invert the bottle and submerge it to a depth of six inches. Angle the mouth of the bottle toward the surface of the water, scooping it full of water. Place the cap on the bottle, making sure it is secure. Use permanent ink to label the bottles with the sample depth.
- 7
  Place the sample bottles in a dark cooler. Record the location where the sample was taken on a sampling form. Sign and date the form.
- 8
  Pack the cooler with ice. Place the sample form in a sealed zip-close plastic bag and tape it to the underside of the cooler lid. Secure the cooler with strapping tape; affix a shipping label and ship to a lab within 48 hours.
- 9
  Follow the above procedures when collecting water samples for phosphorus testing. Use the brown water sample bottles.

Nature