What is chlorophyll?

Chlorophyll is the green pigment found in plants, and it’s vital for photosynthesis. Measuring chlorophyll in water is important to estimate the abundance of phytoplankton. If a high level of chlorophyll is detected, it is an indication that a high level of phytoplankton is present in the water.

The abundance of phytoplankton is related to the availability of nutrients, and to the levels of phosphate and nitrate within the water. This could be caused by a pollutant entering the water, for example agricultural runoff or sewage overflow. The natural chlorophyll levels in water fluctuate over time. For example, levels are often higher after rainfall, and during the summer when water temperatures and light levels are increased. Measuring chlorophyll in water enables you to gain an understanding of the natural levels of chlorophyll present in the water, and to recognise if there is a change, which could be an indication that a pollutant has entered the water.



Aquaread’s chlorophyll meter

Aquaread’s chlorophyll meter is a submersible, fixed response fluorometer. The electrode transmits an excitation beam in the blue wavelength, which induces the chlorophyll to fluoresce. The chlorophyll sensor then measures the resultant light fluorescence by chlorophyll in the red wavelength. This fluorescence is directly proportional to the concentration of chlorophyll. Measuring chlorophyll in water in the field will never be as accurate as in the lab, using either cell counting or analysis of molecular chlorophyll after its extraction from cells, but it has its benefits as outlined above.

Some factors affecting the accuracy of the fluorometer include: interference from other microbiological species and compounds that fluoresce at similar wavelengths, differences in the fluorescent response between various species of phytoplankton, temperature, ambient light, and turbidity.

To ensure consistent and reliable results careful calibration of the chlorophyll meter is essential. The fluorometer gives readings of levels of chlorophyll in water in a range of 0 – 500 ug/L (ppb) with a resolution of 0.1 ug/L.

Why measure chlorophyll in the field?

Using a portable chlorophyll meter in the field allows near real-time data to be collected. It is a relatively simple method that, although indirect, allows measurements to be made in situ and in a time series. A chlorophyll meter is an ideal choice for researchers who are interested in detecting the presence or absence of chlorophyll, and measuring relative fluorescent changes that can be used as an indication of increasing or decreasing concentrations.

Using a chlorophyll meter allows you to identify temporal and vertical patterns of phytoplankton biomass in a water body. This method is an effective measure of trophic status, a potential indicator of maximum photosynthetic rate and a measure of water quality. Another benefit of measuring chlorophyll in water is that phytoplankton react quickly to pulsed nutrient inputs that might otherwise go undetected by regular nutrient sampling.


Aquaread’s water quality testing equipment

Aquaread’s chlorophyll sensor fluorometer is an optional optical electrode that is used with any of the Aquaprobe multiparameter water testing probes. Our rugged water testing equipment is specifically designed for testing chlorophyll in the field. The AP-7000 is designed with long term deployment in mind. It features a self cleaning function to maximise deployment time and allows the addition of up to 6 sensors for the user to choose which parameters they want to measure.


Image of the AP-7000 aquaprobe by Aquaread

The aquaprobe AP5000

The aquaprobe AP2000







The AP-5000 is portable and has sockets to accommodate four additional electrodes, whereas the ultra-portable AP-2000 can take one optional ISE and one optical electrode. If you only need to measure one parameter we have the AP-LITE, which is a small body that takes one optical electrode, such as a chlorophyll sensor. Your choice of Aquaprobe will depend on the application that it is intended for.

Get monitoring with Aquaread

If you would like any further information about our portable chlorophyll meter, or about water quality monitoring in general, please don’t hesitate to get in touch. Click here to see our product range.

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