57
Such instruments must be calibrated in the field in order to reflect the particular
environmental conditions of the phytoplankton community and must be recalibrated
as conditions change. These instruments, described below, are a subset of the now
common submersible fluorometer family of instruments used for the various other
analyses described above. Many designs feature a common platform where the light
source and filters are substituted to specifications as the application may require.
Early submersible fluorometers adaptable to modern CTD/carrousel arrays
incorporated traditional cast iron optical benches with various lenses, xenon lamps,
and photomultiplier detectors housed in a cylindrical pressure hull. Power requirements were substantial, severely limiting autonomous operation. Instruments in use
today for the most part use LED sources and photodiode detectors, vastly reducing
bulk, weight, and power consumption. Single optical excitation and emission bands
are selected using optical filters. Various instrument architectures are available for
pumped or unpumped operation. Most common is an external cell array with
orthogonal light source and detector aimed at a small volume of the seawater
medium. Some instruments mount two opposed light sources. External optical
arrays may allow installation of optical head housings with inlet and outlet suitable
for pumped operation. A more innovative solution is an axial flow-through optical
pipe essentially transporting the optical head into the instrument housing. These
instruments operate at low power (7–20 V DC) drawing less than 100 mA (Fig. 2.17).
For shipboard or mooring applications, data generated by fluorometers and other
instruments are usually coupled to the primary onboard environmental data systems; CTDs or thermosalinographs, together with the now common oxygen, pH,
and pCO 2 sensor data. Ancillary data from these instruments is appended to the
CTD and GPS data streams for telemetry.
2.5.2 Automated Sell Sorting, Counting, and Bio-optical
Characterization
A number of phytoplankton species including some diatoms and, most notably,
dinoflagellates are capable of producing highly toxic water-soluble compounds that
affect marine as well as terrestrial organisms. Human consumption of contaminated
shellfish causes poisoning leading to severe gastric and neurological distress and
resulting, in extreme, in paralysis and eventual death. Even inhalation of aerosols of
ocean foam containing the organisms or their detritus can result in illness. Their
proliferation in coastal environments has been attributed to anthropogenic eutrophication that, under appropriate environmental circumstances, promotes their
unchecked growth resulting as harmful algal blooms (HABs). Chlorophyll biomass
determination provides only an indication of algal biomass. Fortunately, automated
means of determining the composition of phytoplankton assemblages and a mature
understanding of the role of turbulence and nutrient supplies on their temporal evolution are now beginning to allow an operational approach to forecasting HABs.
2.5 Sensors for Biological Compounds and Processes: Chlorophyll, Accessory…
Such instruments must be calibrated in the field in order to reflect the particular
environmental conditions of the phytoplankton community and must be recalibrated
as conditions change. These instruments, described below, are a subset of the now
common submersible fluorometer family of instruments used for the various other
analyses described above. Many designs feature a common platform where the light
source and filters are substituted to specifications as the application may require.
Early submersible fluorometers adaptable to modern CTD/carrousel arrays
incorporated traditional cast iron optical benches with various lenses, xenon lamps,
and photomultiplier detectors housed in a cylindrical pressure hull. Power requirements were substantial, severely limiting autonomous operation. Instruments in use
today for the most part use LED sources and photodiode detectors, vastly reducing
bulk, weight, and power consumption. Single optical excitation and emission bands
are selected using optical filters. Various instrument architectures are available for
pumped or unpumped operation. Most common is an external cell array with
orthogonal light source and detector aimed at a small volume of the seawater
medium. Some instruments mount two opposed light sources. External optical
arrays may allow installation of optical head housings with inlet and outlet suitable
for pumped operation. A more innovative solution is an axial flow-through optical
pipe essentially transporting the optical head into the instrument housing. These
instruments operate at low power (7–20 V DC) drawing less than 100 mA (Fig. 2.17).
For shipboard or mooring applications, data generated by fluorometers and other
instruments are usually coupled to the primary onboard environmental data systems; CTDs or thermosalinographs, together with the now common oxygen, pH,
and pCO 2 sensor data. Ancillary data from these instruments is appended to the
CTD and GPS data streams for telemetry.
2.5.2 Automated Sell Sorting, Counting, and Bio-optical
Characterization
A number of phytoplankton species including some diatoms and, most notably,
dinoflagellates are capable of producing highly toxic water-soluble compounds that
affect marine as well as terrestrial organisms. Human consumption of contaminated
shellfish causes poisoning leading to severe gastric and neurological distress and
resulting, in extreme, in paralysis and eventual death. Even inhalation of aerosols of
ocean foam containing the organisms or their detritus can result in illness. Their
proliferation in coastal environments has been attributed to anthropogenic eutrophication that, under appropriate environmental circumstances, promotes their
unchecked growth resulting as harmful algal blooms (HABs). Chlorophyll biomass
determination provides only an indication of algal biomass. Fortunately, automated
means of determining the composition of phytoplankton assemblages and a mature
understanding of the role of turbulence and nutrient supplies on their temporal evolution are now beginning to allow an operational approach to forecasting HABs.
2.5 Sensors for Biological Compounds and Processes: Chlorophyll, Accessory…