Paul J F Geerders’s scientific contributions

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Publications (2)


High frequency monitoring reveals phytoplankton dynamics
  • Article

January 2005

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116 Reads

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71 Citations

Journal of Environmental Monitoring

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Paul J F Geerders

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Richard R Jonker

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. For common phytoplankton growth rates basic signal processing theory yields a minimum monitoring frequency of once per day, which is much more than applied in standard practice. To assess the nature of this discrepancy we followed the behaviour of about 40 groups of organisms/particles found in the Oude Rijn river by a two-week daily cytometric analysis. Particle counts of the 20 most abundant groups are shown. Their variation rate and magnitude confirm that daily sampling is needed to follow such ecosystems in detail. It is shown that limiting the monitoring to the "coarse line" does not allow a correspondingly decreased sampling frequency. Automated systems may fill the gaps between the microscopical examinations by gathering highly frequent information. The information depth of bulk measurements is poor however, and not used as such. The data shown here demonstrate that modern scanning flow cytometry (SFC) offers an information depth close to the taxonomic level. In the past decade, acquisition and operation costs of these systems have come down considerably, whereas operation is hands free, even in situ and submerged, and data analysis has become more efficient. SFC is used most efficiently complementary to microscopical analyses for mutual validation. In these cases it presents a realistic solution to generate the essential high frequency observations required to assess ecosystem variability.


Innovative technologies to monitor plankton dynamics

August 2004

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13 Reads

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5 Citations

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 analysis of samples takes much time, and therefore only detects low frequency changes. Automated systems such as scanning cytometry can fill the gaps between the microscopical examinations by gathering information on rapid, high frequency changes, and thus permit real-time, in situ operational monitoring. This paper demonstrates that modern scanning flow cytometry is a practical means to obtain real-time information on changes in plankton communities in marine, coastal and estuarine waters.

Citations (2)


... The desire for more readily available sensors for AUVs is identified, especially biological and chemical sensors. Many typically lab-based sensors are being developed for in situ use, including a flow cytometer (Tarran et al. (2001); Dubelaar and Geerders (2004)), a mass spectrometer (Short et al. (2001)), Raman spectrometer * ), yet power and size requirements of AUVs are now being satisfied in only a few cases. An example of a need not yet met is for microbial samplers for bacteria and viruses (sewage indicators, underwater hot vents, sub-glacial lakes, fish farms to monitor disease dispersion). ...

Reference:

Masterclass in AUV Technology for Polar Science
Innovative technologies to monitor plankton dynamics
  • Citing Article
  • August 2004

... Bailey-Watts, 1981;Rose et al., 2021;Wei et al., 2020). Furthermore, for monitoring routines where automated high frequency sensors are not used, fortnightly or monthly lake sampling is common (Dubelaar et al., 2004;Marcé et al., 2016;Spaulding et al., 2024), and so there are likely many existing datasets for which these findings are applicable. Rousso et al. (2020) also found that almost half (44.4 %) of the reviewed studies with similar input data to the present study used less than five years data. ...

High frequency monitoring reveals phytoplankton dynamics
  • Citing Article
  • January 2005

Journal of Environmental Monitoring