59
At the heart of modern environmental flow cytometry is the ability to funnel
sample cells in the seawater medium sheathed in a fluid carrier stream to achieve
single cell passage through the sensing volume. Multiple wavelength laser probes
allow both fluorescence and scattering analysis of individual cells (Dubelaar et al.
1999; Dubelaar and Jonker 2000). A compact system incorporating two excitation
lasers, multiple fluorescence detectors, and multiple scatter sensors is commercially
available in configurations for either laboratory operation or for field deployment
mounted as a submersible profiling unit or in a buoy package. Dugenne et al. (2015)
have demonstrated the feasibility of detecting and following the evolution of a HAB
using a buoy-mounted instrument but operational long-term deployment of such
automated flow cytometers is still hampered by the complexity of the instrument
and its relatively short autonomy.
The benchtop instrument originally described by Sieracki et al. (1998) provides
an alternative to laser flow cytometry. A seawater stream is passed through a flat
optical chamber where digital images and wide-band fluorescence signals (435–
470 nm excitation; 520–700 nm emission) are recorded. Simultaneous imaging and
fluorescence peak identification allows selecting particles with similar size, aspect
ratio, and fluorescence properties. Digital imaging allows automated shape recognition so the associated software systems may be trained to recognize and quantify
individual species. These instruments are suitable for laboratory or shipboard work
and have successfully monitored HABs bloom evolution (Buskey and Hyatt 2006)
(Fig. 2.18).
2.5.3 Remote Sensing of Photosynthetic Pigments
Operational coastal observing applications of satellite-derived ocean color data
focus on the occurrence, distribution, and fate of algal blooms which may be health
hazards or may constitute navigation and aesthetic nuisances. Blondeau-Patissierre
et al. (2014) provide a detailed and up-to-date review of the use of satellite ocean
color data for detection mapping and analysis of phytoplankton blooms. They note
the severe problems yet faced for accurate retrievals in the coastal zone and highlight the value of coupling ocean color data to additional environmental data sets,
statistical methods, and numerical models.
Several substances either dissolved or dispersed in the water column interact
with visible light and the adjacent IR and UV bands allowing their detection in nearsurface waters using satellite-borne radiometers. Phytoplankton photosynthetic pigments, dissolved organic matter, mineral phytoplankton inclusions, and suspended
nonphotosynthetic particulate matter are among the members of this photoactive
class of substances. Detection of photosynthetic pigments and dissolved organic
matter is discussed below. Biologically generated calcium carbonate inclusions
common to the coccolithophores (planktonic single celled eukaryotic algae) are
readily apparent in images of massive blooms occurring in surface waters at temperate and polar latitudes. Suspended nonphotosynthetic particulate matter is of limited
2.5 Sensors for Biological Compounds and Processes: Chlorophyll, Accessory…
At the heart of modern environmental flow cytometry is the ability to funnel
sample cells in the seawater medium sheathed in a fluid carrier stream to achieve
single cell passage through the sensing volume. Multiple wavelength laser probes
allow both fluorescence and scattering analysis of individual cells (Dubelaar et al.
1999; Dubelaar and Jonker 2000). A compact system incorporating two excitation
lasers, multiple fluorescence detectors, and multiple scatter sensors is commercially
available in configurations for either laboratory operation or for field deployment
mounted as a submersible profiling unit or in a buoy package. Dugenne et al. (2015)
have demonstrated the feasibility of detecting and following the evolution of a HAB
using a buoy-mounted instrument but operational long-term deployment of such
automated flow cytometers is still hampered by the complexity of the instrument
and its relatively short autonomy.
The benchtop instrument originally described by Sieracki et al. (1998) provides
an alternative to laser flow cytometry. A seawater stream is passed through a flat
optical chamber where digital images and wide-band fluorescence signals (435–
470 nm excitation; 520–700 nm emission) are recorded. Simultaneous imaging and
fluorescence peak identification allows selecting particles with similar size, aspect
ratio, and fluorescence properties. Digital imaging allows automated shape recognition so the associated software systems may be trained to recognize and quantify
individual species. These instruments are suitable for laboratory or shipboard work
and have successfully monitored HABs bloom evolution (Buskey and Hyatt 2006)
(Fig. 2.18).
2.5.3 Remote Sensing of Photosynthetic Pigments
Operational coastal observing applications of satellite-derived ocean color data
focus on the occurrence, distribution, and fate of algal blooms which may be health
hazards or may constitute navigation and aesthetic nuisances. Blondeau-Patissierre
et al. (2014) provide a detailed and up-to-date review of the use of satellite ocean
color data for detection mapping and analysis of phytoplankton blooms. They note
the severe problems yet faced for accurate retrievals in the coastal zone and highlight the value of coupling ocean color data to additional environmental data sets,
statistical methods, and numerical models.
Several substances either dissolved or dispersed in the water column interact
with visible light and the adjacent IR and UV bands allowing their detection in nearsurface waters using satellite-borne radiometers. Phytoplankton photosynthetic pigments, dissolved organic matter, mineral phytoplankton inclusions, and suspended
nonphotosynthetic particulate matter are among the members of this photoactive
class of substances. Detection of photosynthetic pigments and dissolved organic
matter is discussed below. Biologically generated calcium carbonate inclusions
common to the coccolithophores (planktonic single celled eukaryotic algae) are
readily apparent in images of massive blooms occurring in surface waters at temperate and polar latitudes. Suspended nonphotosynthetic particulate matter is of limited
2.5 Sensors for Biological Compounds and Processes: Chlorophyll, Accessory…