indicate normal seasonal changes in these communities or may indicate long term
ecosystem changes, due to either natural or anthropogenic causes. Thus, one
achievement of CREWS station long term monitoring via the methods described here
may be the elucidation of the causes and implications of variation in the shading
properties of CDOM on coral health.
8.1.3. Fluorescence Efficiency
Previous studies have shown reduction in coral fluorescent yield as a coral stress
response to, for example, high sea temperature (Jones, et al. 2000) or exposure to
intense UVR (Jones and Hoegh-Guldberg 2001). This reduction in fluorescent yield
typically precedes either mild or extensive coral bleaching, including the expulsion of
zooxanthellae from the coral host. Variation in fluorescent yield during a diurnal cycle
is larger than the night-to-night, dark-adapted variation in efficiency observed over
time. Monitoring of the nighttime fluorescence yield of corals provides an early
indication of the onset of coral bleaching, prior to when subjective determination of
changes in the corals' color can be observed. For this reason, select CREWS stations
have been designed to incorporate a direct measure of fluorescent yield to provide
better coral bleaching predictions. Long term monitoring of fluorescence yield
provides an additional baseline from which the expert system software can calculate
deviation and determine significance.
The typical method for determining fluorescent yield is via pulse amplitude
modulation (PAM) fluorometry. PAM fluorometers have been used at individual
locations and with variable sampling intervals to determine photosynthetic health, both
for terrestrial plants and, more recently, for submerged vegetation and corals (for a
review, see Fitt et al. 2001). The next generation PAM fluorometer, a multi-sensor
“monitoring PAM” designed for long-term underwater deployments, has been
incorporated into the CREWS station architecture (see Figures 6-8). Typical PAM
fluorometry output data (Figure 9) provide the dark adapted background fluorescence
(F 0 ) and the maximum fluorescence observed when the coral is exposed briefly to a
saturating pulse of broad spectrum light (F m ). The instrument then calculates the
variation in fluorescence (F v = (F m -F 0 )/F m ) which is the fluorescent yield. In a
monitoring PAM deployment, the time series data will show very low values of F v
during the day since the corals undergo dynamic photoinhibition, essentially
eliminating a portion of the excess light energy from photosystem II for protection from
cellular damage (Lesser and Gorbunov 2001). However, in the nighttime hours (a
subjective period recognized by the expert system software, cf. Table 2), the F v values
quickly rise to a stable range, with healthy corals achieving values as high as 0.65.
Higher values are exhibited in conditions favorable for coral growth, while lower
values are observed when corals are stressed. Subjective data ranges are applied to
these values to allow expert system-based early warnings of coral bleaching events.
149
Meteorological and Oceanographic Instrument Array
ecosystem changes, due to either natural or anthropogenic causes. Thus, one
achievement of CREWS station long term monitoring via the methods described here
may be the elucidation of the causes and implications of variation in the shading
properties of CDOM on coral health.
8.1.3. Fluorescence Efficiency
Previous studies have shown reduction in coral fluorescent yield as a coral stress
response to, for example, high sea temperature (Jones, et al. 2000) or exposure to
intense UVR (Jones and Hoegh-Guldberg 2001). This reduction in fluorescent yield
typically precedes either mild or extensive coral bleaching, including the expulsion of
zooxanthellae from the coral host. Variation in fluorescent yield during a diurnal cycle
is larger than the night-to-night, dark-adapted variation in efficiency observed over
time. Monitoring of the nighttime fluorescence yield of corals provides an early
indication of the onset of coral bleaching, prior to when subjective determination of
changes in the corals' color can be observed. For this reason, select CREWS stations
have been designed to incorporate a direct measure of fluorescent yield to provide
better coral bleaching predictions. Long term monitoring of fluorescence yield
provides an additional baseline from which the expert system software can calculate
deviation and determine significance.
The typical method for determining fluorescent yield is via pulse amplitude
modulation (PAM) fluorometry. PAM fluorometers have been used at individual
locations and with variable sampling intervals to determine photosynthetic health, both
for terrestrial plants and, more recently, for submerged vegetation and corals (for a
review, see Fitt et al. 2001). The next generation PAM fluorometer, a multi-sensor
“monitoring PAM” designed for long-term underwater deployments, has been
incorporated into the CREWS station architecture (see Figures 6-8). Typical PAM
fluorometry output data (Figure 9) provide the dark adapted background fluorescence
(F 0 ) and the maximum fluorescence observed when the coral is exposed briefly to a
saturating pulse of broad spectrum light (F m ). The instrument then calculates the
variation in fluorescence (F v = (F m -F 0 )/F m ) which is the fluorescent yield. In a
monitoring PAM deployment, the time series data will show very low values of F v
during the day since the corals undergo dynamic photoinhibition, essentially
eliminating a portion of the excess light energy from photosystem II for protection from
cellular damage (Lesser and Gorbunov 2001). However, in the nighttime hours (a
subjective period recognized by the expert system software, cf. Table 2), the F v values
quickly rise to a stable range, with healthy corals achieving values as high as 0.65.
Higher values are exhibited in conditions favorable for coral growth, while lower
values are observed when corals are stressed. Subjective data ranges are applied to
these values to allow expert system-based early warnings of coral bleaching events.
149
Meteorological and Oceanographic Instrument Array