Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from ancient Greek: chloros = green and phyllon = leaf. Chlorophyll absorbs light most strongly in the blue and red but poorly in the green portions of the electromagnetic spectrum, hence the green color of chlorophyll-containing tissues like plant leaves.  The pigments are named after the wavelength (in nanometers) of their red-peak absorption maximum. The identity, function and spectral properties of the types of chlorophyll in each photosystem are distinct and determined by the protein structure. 

Chlorophyll is vital for photosynthesis, which allows plants to obtain energy from light. Chlorophyll molecules are specifically arranged in and around pigment protein complexes called photosystems which are embedded in the chloroplasts. In these complexes, chlorophyll serves two primary functions. The function of the vast majority of chlorophyll (up to several hundred per photosystem) is to absorb light and transfer that light energy by resonance energy transfer to a specific chlorophyll pair in the reaction center of the photosystems. Because of chlorophyll’s selectivity regarding the wavelength of light it absorbs, areas of a leaf containing the molecule will appear green.

 

Spectral Analysis of Extract

To measure chlorophyll a concentration, a composite sample of the lake column within the photic zone is collected on a monthly basis during the growing season.  The water sample is “composited” because the purpose is to calculate an average chlorophyll concentration within the photoic zone.  The photic zone is where plants (algae and other aquatic plants) have sufficient sunlight to permit photosynthesize. Below the photic zone, there is not enough sunlight for most plants to photosynthesize.  The depth of the photoic zone can be estimated using the seechi disk depth.  The integrated sample allows us to examine the water column where phytoplankton live (i.e. the part of the water column with enough sunlight for photosynthesis to occur). 

If the composite sample is to be filtered in the laboratory, the sample is place in a dark bottle and wrap with aluminum foil and placed in a cooler.   In the laboratory, a given volume of the sample is filtered using a glass fiber filter.  All of the algae and other suspended particles in the water will collect on the filter paper.  The filter paper is then processed, ground, and leached to extract the chlorophyll.  Once extracted from the protein structure and dissolved into a solvent (such as Acetone or Methanol), these chlorophyll pigments can be separated in a simple paper chromatography measures or a  view a spectral analysis using a spectrophotometer.

If you would like information related to our laboratory services related to lake trophic status monitoring (Seechi, Total Phosphate, Chlorophyll, Total Kjeldahl Nitrogen, Nitrate+Nitrite, Phytoplankton, Zooplankton), please email lake trophic monitoring.  Currently, the cost for the chlorophyll analysis is charged at a rate of $ 60.00 per sample.  

Announcement - The laboratory can also conduct testing and screening for microcystin.  Microcystins (MCs) are naturally occurring hepatotoxins (liver toxins) produced by certain genera of cyanobacteria.  Sublethal levels of microcystins can cause intestinal and liver dysfunction in animals and humans. Death can result from severe liver damage and shock following ingestion of high toxin concentrations.  Wilkes University can conduct microcystin screening as part of the lake assessment.  Currently, the cost for the screening analysis is $ 50.00 per sample, plus sampling costs.  Recommended levels - Drinking Water n
(WHO < 1 ppb; Lakes - action level at 20 ppb).  Currently - We have tested lakes in NEPA that have microcystin levels over 10 times this action level.
If you are interested in participating in this screening, please email microcystin monitoring. 

If you are interested in lake monitoring, citizen monitoring/training, QC/QA Programs, Monitoring Plan Design and outreach efforts, including lake acidity, trace metals, and the C-SAW Program (Free Assistance to Watershed Groups), please visit the following link:  Consortium for Scientific Assistance to Watersheds.