Total Phosphorus and Chlorophyll α

Expanded monitoring for total phosphorus and chlorophyll α concentration

Overview of process

To measure total phosphorus and chlorophyll α concentration, you will take an integrated water sample from the lake every month throughout the growing season.  The water sample is “integrated” because it represents a sample of the water column from the surface to a depth of 6 feet.  The integrated sample allows us to examine the water column where phytoplankton lives (i.e. the part of the water column with enough sunlight for photosynthesis to occur).  The sample is partitioned in a sample bottle and a specific volume of water is filtered.  All of the algae (and other suspended particles) in the water will collect on the filter, which is then analyzed in the laboratory for chlorophyll α concentration.

Sampling checklist

Before going out on the lake to make your Secchi disk reading, make sure that you have everything you need and the weather conditions are okay for sampling! Please confirm everything on this checklist:


  • Sunny / Partly Sunny / Partly Cloudy
  • Winds calm to breezy (NO WHITECAPS!!)

Date and time of day:

  • Between 10 a.m. and 4 p.m.

Do you have:

  • Secchi disk?
  • Boat anchor?
  • Sampling instructions?
  • Data forms?
  • Pen/pencil

Equipment for Chlorophyll a and Total Phosphorus Sample Collection:

  • Filtering apparatus ~ cap, upper chamber, filter support plate & receiver
  • Pitcher
  • 250 milliliter graduated cylinder
  • 7 cm filter paper (in plastic case) with Tweezers
  • Hand-operated pump with clear tubing
  • PVC pipe (for sample collection)
  • Sample bottles ~ 1--6 ml opaque (chlorophyll α ) & 1-- 125 ml clear (total phosphorus)
  • Styrofoam mailer
  • Sharpie pen

Download paper checklist

Total phosphorus and chlorophyll α sampling gear

Line illustration of sampling gear which includes: a pitcher, graduated cylinder, filtering apparatus, hand pump, 125 ml. TP bottle, 60 ml. opague chl bottle, and filter paper.

How to collect the samples

Table 1

Secchi DepthMinimum Volume of Water to Filter
< 1 ft50 mls
1-1.5 ft100 mls
>1.5-2.5 ft200 mls
>2.5-3.5 ft300 mls
>3.5-6 ft.500 mls
>6-9 ft800 mls
>9-16 ft1000 mls
>16 ft1500 mls

">" means "greater than"

Illustration A: Chlorophyll-α filtration apparatus
Illustration B: How to pack the styrofoam cooler for shipping.