• Home
  • George BJ Dubelaar
George BJ Dubelaar

George BJ Dubelaar
CytoBuoy b.v.

Master of Science

About

33
Publications
6,677
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,400
Citations

Publications

Publications (33)
Article
Full-text available
The recent development of biological sensors has extended marine plankton studies from conducting laboratory bench work to in vivo and real-time observations. Flow cytometry (FCM) has shed new light on marine microorganisms since the 1980s through its single-cell approach and robust detection of the smallest cells. FCM records valuable optical prop...
Article
Full-text available
In this paper we review the technologies available to make globally quantitative observations of particles in general—and plankton in particular—in the world oceans, and for sizes varying from sub-microns to centimeters. Some of these technologies have been available for years while others have only recently emerged. Use of these technologies is cr...
Article
Full-text available
The ability to quantify vital aquatic organisms in the 2–50 µm size range was compared between five different flow cytometers and several different microscopes. Counts of calibration beads, algal monocultures of different sizes as well as organisms in a Wadden Sea sample were compared. Flow cytometers and microscopes delivered different bead concen...
Conference Paper
Full-text available
Heterotrophic microorganisms represent the main consumers and mineralisers of the organic matter in the ocean as well as in inland waters. These organisms are in strong interaction with phytoplankton and higher trophic levels and may react quickly to environmental changes. In contrast with phytoplankton, due to the lack of photosynthetic pigments t...
Article
Full-text available
A methodology is developed to derive the backscattering cross section of individual particles as measured with the CytoSense (CytoBuoy b.v., NL). This in situ flow cytometer detects light scatter in forward and sideward directions and fluorescence in various spectral bands for a wide range of particles. First, the weighting functions are determined...
Article
Adverse effects of invasive alien species (IAS), or biological pollution, is an increasing problem in marine coastal waters, which remains high on the environmental management agenda. All maritime countries need to assess the size of this problem and consider effective mechanisms to prevent introductions, and if necessary and where possible to moni...
Chapter
Full-text available
IntroductionPlankton and their Importance Particles in Surface WaterPhytoplanktonDistributions in the Aquatic EnvironmentConsiderations for using Flow Cytometry Analytical ApproachLimitations and Pitfalls of using Biomedical InstrumentsInstrument Modification and Specialized CytometersSizing and Discrimination of CellsMore Information per Particle:...
Article
Phytoplankton is an important water quality indicator because of its high species differentiation, growth rates and responsiveness to environmental actuators. The new European Water Framework Directive calls for assessment of the duration, intensity and succession of phytoplankton blooms to determine the ecological status of various types of waters...
Article
Phytoplankton is an important water quality indicator by its high species differentiation, fast growth rates and responsiveness to environmental actuators. National and regional regulations and directives call for a detailed assessment of phytoplankton blooms as an indicator to determine the ecological status of various types of waters. Microscopic...
Article
Phytoplankton is an important water-quality indicator due to its high species differentiation, fast growth rates and responsiveness to environmental actuators. National and regional regulations and directives call for a detailed assessment of phytoplankton blooms as an indicator of the ecological status of various types of waters. Microscopic analy...
Article
Phytoplankton play a pivotal role in marine ecosystems — collectively fuelling the food web, sometimes forming nuisance blooms, and implicated in climate control. They are sensitive bioindicators in marine ecosystems. Thus, knowledge of species composition, distribution and abundance in the worlds oceans is essential. Traditionally such data have b...
Article
Full-text available
An overview is presented on flow cytometry as a tool for counting, analysis and identification of phytoplankton species and groups. The paper covers basics on the analysis technique and instrumentation such as the measuring principle, the type of instrument, limitations and pitfalls with phytoplankton samples and sample handling and preprocessing....
Article
Full-text available
While the performance of biological sensors in real time monitoring networks is limited to bulk values like chlorophyll fluorescence, in practice the implementation of automated phytoplankton taxonomy remains a remote option. Aiming to reduce this gap we developed a flow cytometer called CytoBuoy for autonomous in situ operation, for instance in a...
Article
The high costs of microscopical determination and counting of phytoplankton often limit sampling frequencies below an acceptable level for the monitoring of dynamic ecosystems. Although having a limited discrimination power, flow cytometry allows the analysis of large numbers of samples to a level that is sufficient for many basic monitoring jobs....
Article
We introduce a method for the determination of size distributions of natural Microcystis aeruginosa colonies. The analyses can be done on a routine basis with the (Eur)OPA flow cytometers. Colony sizes expressed as the number of mean single cells per colony are obtained using the ratio between the measured fluorescence per colony and the mean fluor...
Article
The large range in concentrations and cell-sizes of algal cells and colonies and the large variety of cell types are the main reasons for developing a dedicated cytometer for the analysis of phytoplankton. A European Community funded consortium has developed the EurOPA cytometer, which is easily transported and can be operated at sea. With the EurO...
Article
We introduce a method for the determination of size distributions of natural Microcystis aeruginosa colonies. The analyses can be done on a routine basis with the (Eur)OPA flow cytometers. Colony sizes expressed as the number of mean single cells per colony are obtained using the ratio between the measured fluorescence per colony and the mean fluor...
Article
A flow cytometer was developed for the high-speed “sorting” of desired cells by selectively irradiating (zapping) the undesired cells from a population. After previous efforts to photoinactivate cells with photosensitizers had failed, it was decided to exploit the photosensitivity of the cell's DNA at 257 nm. It was shown that a 257 nm laser output...
Conference Paper
Today's monitoring of phytoplankton abundance and composition in surface waters can be made more efficient by improving logistic and physical compatibility of analysis techniques. Particularly the microscopical identification and counting of phytoplankton is a time consuming, not quantitative technique, unsuited for early warning, automation and in...
Article
The large range in concentrations and cell-sizes of algal cells and colonies and the large variety of cell types are the main reasons for developing a dedicated cytometer for the analysis of phytoplankton. A European Community funded consortium has developed the EurOPA cytometer, which is easily transported and can be operated at sea. With the EurO...
Article
A Large Volume Reflectometer (LVR) for the measurement of reflection properties of surface water is presented. The instrument and its function are described. A protocol for measurements using the collimated illumination is described. With this setup reflection spectra of demi water filtered over 0.45 microns pore size filters and untreated tap wate...
Article
Full-text available
New, optical, approaches to automatize and to accelerate the analysis of algae are discussed. Firstly, the application of flow cytometric analysis will be presented. This technique is based on classification of particles in flow by measuring several optical properties per individual particle. Characteristics of the Optical Plankton Analyser, a flow...
Article
The design criteria for a flow cytometer (FCM) for the analysis of field samples of phytoplankton are described. The criteria are based on the occurrence of a wide variety of particle sizes in field samples, normally at low concentrations. The instrument should be able to analyse cells and colonies from 0.5 to 500 μm diameter and of over 2,000 μm l...
Article
An analysing flow cytometer, the optical plankton analyser (OPA), is presented. The instrument is designed for phytoplankton analysis, having a sensitivity comparable with commercially available flow cytometers, but a significantly extended particle size range. Particles of 500 microns in width and over 1,000 microns in length can be analysed. Samp...
Article
Extinction, absorption, and forward and perpendicular light scatter of the blue-green alga Microcystis aeruginosa with different amounts of intracellular gas vacuoles were determined. The amount of gas vacuoles in the cells was controlled by application of pressure. The presence of the gas vacuoles caused a tenfold increase in perpendicular light s...

Network

Cited By