Measurement principle

The fluorescence of algae (emission at approx. 700nm wavelength) due to excitation by visible light mainly depends on the presence of chlorophyll-a, a common pigment in the plant world. The occurrence of other pigments is typical for the different algae classes. Interactions between these different pigment systems with chlorophyll-a result in a special excitation spectrum for the taxonomical algae classes.

The special patterns of this algae fluorescence - so-called fingerprints - are used in the bbe fluorometers for the quantification of different algae classes. The excitation light sources are LEDs with different wavelengths. The fingerprints of four algae classes and of yellow substances are already stored in the FluoroProbe. Special user-defined fingerprints can also be added.

Advantages of the FluoroProbe

• determination of green algae, blue-green algae (cyanobacteria), diatoms and cryptophytes
• up to 4 other algae classes can be calibrated by the user
• up to 4 measurements per second
• yellow substances correction and compensation of interferences by UV-LED
• reduces the number of required microscopic laboratory examinations
• internal rechargeable batteries
• internal datalogger
• PC software for data analysis
• options: pressure sensor, transmission measurement

Applications

• environmental monitoring
• early warning system for algae blooms in limnological and marine waterways
• bathing water monitoring of blue-green algae (cyanobacteria)
• drinking water monitoring of (toxic) blue-green algae
• pre-warning of the occurrence of poisonous algae (e.g. cyanobacteria toxins)
• detection of chlorophyll and other pigments such as phycocyanine and phycoerythrine, fucoxanthine and peridinine
• aquaculture monitoring
• dam monitoring
• algae distribution in the Arctic/Antarctic
• oceanographic research
• mooring, experiments, continuous analysis
• limnological research
• research and teaching
• tracer measurements

Software

The bbe FluoroProbe software supplied with the instrument facilitates detailed data analysis. All measurement data can be displayed numerically or graphically. Sections of data measurements can be recorded and printed using the zoom function. Data can also be exported to a spreadsheet program (e.g Excel). All settings and calibrations are performed by the software.

The screenshots below show examples of profiles of algae distribution in the Plussee (lake in Northern Germany) recorded in June 1999. The measurements were made at the same location at 10:00 a.m. and 12:00 noon respectively. The chlorophyll of the dinoflagellates was predominant in the group given in yellow. The change in the depth profile can be traced back to a vertical movement of the dinoflagellates, which actively moved to a deeper level due to adaptation to the current nutrient level.

The specific adaptation of the individual algae groups can be detected due to the cryptophytes, the maximum of which was found at about 5 m depth and did not change during the observation period. Blue-green algae and green algae also show a distribution in the depth profile, which is independent of time.

Hydro-Wiper unit to prevent biofouling

The FluoroProbe can now be operated on moored platforms, submersed from buoys or fixed measuring stations using the Hydro-Wiper (made by Zebra-Tech Ltd, NZ). The wiper brushes can be set to periodically clean the lenses of the measuring chamber to remove biofilms and dirt which builds up over long periods of operation.