User guide

Chelsea Technologies Group
FAST
tracka
User Guide HB179 Issue 7.0
Page
5
of
47
1. INTRODUCTION
The FAST
tracka
Fluorimeter offers rapid, real-time, in situ measurements of photosynthetic
characteristics of marine and freshwater phytoplankton. By exposing phytoplankton to a series
of microsecond flashes of blue light at 200 kHz repetition rate, a saturation profile of PSII variable
fluorescence is observed and recorded. Analysis of the observed fluorescence signal and
knowledge of the excitation protocol allows calculations of the absorption cross section of PSII,
the efficiency of photochemical conversion, and the rates of electron transport from PSII to PSI.
The FRR Fluorimeter is designed to measure these parameters on dark adapted and ambient
irradiated samples in situ.
Analysing the saturation profile of variable fluorescence induced by a sequence of fast repetition
flashes allows evaluation of the following parameters:
Fo: background fluorescence yield when all reaction centres open
F: background fluorescence yield under ambient light
Fm: maximum fluorescence yield when all reaction centres closed
τ: time constants of electron transport from PSII to PSI (s)
Additionally, PAR is measured using an external irradiance sensor attached to the instrument.
Including the measured photosynthetic parameters in appropriate models relating fluorescence
and photosynthesis allows calculation of photochemical/nonphotochemical quenching,
photochemical conversion efficiency, and primary production. Other incidental parameters are
recorded by the instrument for monitoring performance and calibration, and include internal
temperature, battery status, and error codes.
The FAST
tracka
may be deployed for profiling or for moored operations. In constant-duty profiling
operations, the FAST
tracka
will continuously log up to 24 h of data at a 1 Hz acquisition rate when
powered from the standard 15 Ah battery pack. In a moored operation, the acquisition lifetime
may be extended to the timescale of months by reducing the flash repetition rate and properly
managing the instrument sleep cycles. The FAST
tracka
may be powered externally through either
the Interface or the Battery external bulkhead connectors, thus removing the limitation of the
standard battery pack.
The FAST
tracka
is designed for maximum user flexibility. A comprehensive software package
operates on an internal microcontroller and handles data collection, primary data reduction, and
basic instrument functions. Data may be stored internally on a PCMCIA flashdisk, exported to a
CTD or similar device over two 0-5 volt scaleable analogue channels, or transmitted serially over
a host cable to a computer or terminal device. For most operations, flashdisk storage is
recommended for simplicity and speed. Analogue interfacing is more complicated due to the
differences between each manufacturer's CTD/logger specifications, and CI does not claim that
the FAST
tracka
is compatible with all CTDs or loggers, especially older or custom models.
However, our technical support team is ready to assist and advise users to interface the
FAST
tracka
to any CTD or analogue logger. Since there is much variability in CTD performance,
older models might require reconfiguration of the instrument analogue output channel or
reconfiguration of the CTD itself. Please contact CI technical services for help with interfacing the
FAST
tracka
with any other intelligent instrument.