78
both increase with increasing depth; R is constant; and Ik
declines. The transition from relatively high irradiance in summer
to relatively low irradiance in winter produces analogous changes
in the values of the photokinetic parameters: P~ and a both
increase, R is constant, and Ik declines.
In general, these observations are consistent with
photosynthetic photoadaptations which are commonly reported.
The
only exception is the observation that R is constant for fl..
granulosa at all depths and seasons. For Acropora spp. (Chalker ~
~., 1983) and for other species (Kawaguti, 1937; Davies 1977,
1980) respiration declines with decreasing irradiance.
Estimated .!!!.. situ rates of instantaneous net photosynthesis
were calculated from equation (8).
Results for December and June
are illustrated in figure 3 and 4, respectively.
There is a newly
homeostatic carbon flux throughout the day from the surface to a
depth of 30 m.
Below 40 m, due to reduced PPFD, net photosynthesis
never closely approximates its potential maximum.
Seasonally,
summer values are considerably higher at any given hour than are
winter values. In addition, the decline in instantaneous net
photosynthesis below 30 m, is far more dramatic in winter than in
summer.
The shapes of the curves in figures 3 and 4 are typical of
those which have been previously observed for corals by means of in
situ respirometers (Wells, 1977). They are also similar to curves
produced by the models of Vollenweider (1965) when the possibility
of photoinhibition is not included.
Diel gross photosynthesis for December and June as calculated
from the integrals of equation (10) are illustrated in figure
(5).
During the summer, diel P/R ratios increase with increasing
depth from the surface to 25 m (12% of daily surface light),
decline slowly to 35 or 40 m (5.8 - 4.1% of daily surface light),
and are projected to decline rapidly thereafter.
During December,
the diel compensation depth is 60 m (1% of daily surface light).
During June, diel P/R ratios increase from the surface to a
depth of 15-20 m (13 - 9.1% of daily summer surface light),
declines slowly to 30 m (4.5% of daily summer surface light), and
declines rapidly thereafter.
During June, the compensation depth
is 45 m (1.6% of daily summer surface light).
both increase with increasing depth; R is constant; and Ik
declines. The transition from relatively high irradiance in summer
to relatively low irradiance in winter produces analogous changes
in the values of the photokinetic parameters: P~ and a both
increase, R is constant, and Ik declines.
In general, these observations are consistent with
photosynthetic photoadaptations which are commonly reported.
The
only exception is the observation that R is constant for fl..
granulosa at all depths and seasons. For Acropora spp. (Chalker ~
~., 1983) and for other species (Kawaguti, 1937; Davies 1977,
1980) respiration declines with decreasing irradiance.
Estimated .!!!.. situ rates of instantaneous net photosynthesis
were calculated from equation (8).
Results for December and June
are illustrated in figure 3 and 4, respectively.
There is a newly
homeostatic carbon flux throughout the day from the surface to a
depth of 30 m.
Below 40 m, due to reduced PPFD, net photosynthesis
never closely approximates its potential maximum.
Seasonally,
summer values are considerably higher at any given hour than are
winter values. In addition, the decline in instantaneous net
photosynthesis below 30 m, is far more dramatic in winter than in
summer.
The shapes of the curves in figures 3 and 4 are typical of
those which have been previously observed for corals by means of in
situ respirometers (Wells, 1977). They are also similar to curves
produced by the models of Vollenweider (1965) when the possibility
of photoinhibition is not included.
Diel gross photosynthesis for December and June as calculated
from the integrals of equation (10) are illustrated in figure
(5).
During the summer, diel P/R ratios increase with increasing
depth from the surface to 25 m (12% of daily surface light),
decline slowly to 35 or 40 m (5.8 - 4.1% of daily surface light),
and are projected to decline rapidly thereafter.
During December,
the diel compensation depth is 60 m (1% of daily surface light).
During June, diel P/R ratios increase from the surface to a
depth of 15-20 m (13 - 9.1% of daily summer surface light),
declines slowly to 30 m (4.5% of daily summer surface light), and
declines rapidly thereafter.
During June, the compensation depth
is 45 m (1.6% of daily summer surface light).