... makes the bbe FluoroProbe a measuring instrument for benthic algae

Many species of algae have adapted their nutrient uptake systems enabling them to survive in shallow water close to the shoreline, where sunlight still penetrates to the sea bed. This habitat is home to benthic algae, ranging from the microscopic to the enormous (Giant Kelp). Such flora, attached to the sea floor sediments, play an essential role in primary production.

In December 2000, the European Water Framework Directive (EU-WFD) came into force. This directive stipulates that the ecological status of waterways must be regurlary assessed. As a result it has become obligatory to study the development of benthic communities in order to satisfactorily assess aquatic ecosystems.

Information:

Brochures:

• bbe FluoroProbe 
• bbe BenthoFluor Kit

Film:

• FluoroProbe promotional video

Whilst macroscopic algae can be easily observed due to their size, the occurrence of the microscopic benthic algae are difficult to record. The necessity for time-consuming microscopy often hinders effective analysis of benthic algal groups.

Now with the aid of the bbe BenthoFluor, it is possible to analyze the benthic algae in-situ and the composition of spectral algae classes. By measuring the amount of red-light fluorescence arising from illumination at different excitation wavelengths, it is possible to determine a quantitative estimate of algal density and its distribution among the different classes. This technique and the necessary algorithm have been well proven for pelagic phytoplankton by extensive application of the bbe submersible FluoroProbe and have now successfully been adapted to measure benthic algae.

Applications

Measurement of benthic algae on sand, stone and in shallow water.

Operation

The BenthoFluor is housed in a watertight, carbon-fiber reinforced case and, during use, is transported in the supplied backpack or placed in a small boat. All the electronics, data processing and storage are confined in this unit, with the light irradiation and subsequent fluorescence being transmitted along a 1.5m fiber-optic cable to a submersible adapter. Different sensor heads are used for different surfaces. The sensor heads ensure a constant distance between the sediment and the fiber-optic cable, and thus a constant intensity of excitation light; they exclude ambient light enabling "adaptation to darkness", and prevent disturbance of the sediment layers. The unit is controlled via a small hand-held waterproof PC (PDA).

Powerful software features

The chlorophyll-a content is displayed in real time within a range of 0-3 µg/cm. Up to three algae classes are measured simultaneously. All data are recorded on the display of the PDA or stored in the datalogger of the BenthoFluor for further analysis. The ability to obtain and evaluate the results on site, i.e. at the place of measurement, makes the BenthoFluor a valuable tool in benthic algae analysis.

The BenthoFluor kit comes with bbe software for use with Windows and uses spectral fingerprints of standardised algae from laboratory cultures, but also permits the calibration of user-defined algae as a special class.

The BenthoFluor is a versatile instrument. It can be converted into a submersible FluoroProbe within half an hour by simply removing of the cable holder with the fiber optics. Installation of the parameter set for FluoroProbe operations requires only a PC and FluoroProbe software.

 

Specifications of the bbe Benthofluor Kit

Measurands

• total chlorophyll [µg Chl-a/cm²]
• concentration of green algae [µg Chl-a/cm²]
• concentration of blue algae [µg Chl-a/cm²]
• concentration of diatoms [µg Chl-a/cm²]