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FlowCAM

General

Phytoplankton forms the basis of the food web, contains species that are toxic and is a good bio-indicator of environmental changes. Variations in phytoplankton communities may impact a wide range of species, ranging from zooplankton and fish to seabirds and marine mammals. However, studies of plankton are difficult to carry out because of their high diversity and spatiotemporal variability. In addition, traditional identification techniques are time-consuming and require highly qualified taxonomists.

 

Infrastructure

The Flanders Marine Institute (VLIZ) installed a Flow Cytometer And Microscope (FlowCAM) as part of the Belgian LifeWatch observatory. The FlowCAM is and automated technique for particle enumeration that uses flow cytometry and microscopy. This allows the digitalization by a set of images of the organisms present in a water sample.

From May 2017 onwards, phytoplankton is sampled at 9 onshore stations every month; and every season, the sampling occurs at 17 on and offshore stations. The samples are fixed with Lugol and stored for its posterior analysis. Once in the Marine Station Ostend (MSO), the samples are processed by the FlowCAM at different magnifications (4x and 10x) to obtain good resolution images of all the size ranges of interest, primarily nano- and micro-phytoplankton (15 – 300 µm). A gray-scale camera is used because it offers higher resolution quality for species identification and because of the fixed samples do not present fluorescent phytoplankton pigments. However, with the FlowCAM it would be possible to process the samples in real time without preservation based on the fluorescence of the pigments.

Once the pictures are obtained, the pictures are processed with a software included in the FlowCAM (VisualSpreadsheet). This software makes automatic classifications into taxonomical groups by building statistical filters based on the particles properties of libraries. Those libraries are created by the operator to identify specific taxa with similar properties. Finally, the operator needs to verify the automatic classification. It is necessary to optimize the statistical filters and libraries in order to improve the identification accuracy of the FlowCAM.

 

    

Left: Location of the sampling stations in the Belgian Part of the North Sea. - Right: FlowCAM collage from a sample at 4x magnification.