75
In suitable habitats, reef-building corals are abundant at all
depths within the photic zone or approximately from 100% to 1% of
the surface light intensity. It is not surprising that
photosynthetic photoadaptations have been observed in comparisons
of P-I curves for corals growing at different depths (Kawaguti,
1937; Wethey and Porter, 1976a,b; Davies, 1977,1980), in light and
shade environments at the same depth (Falkowski and Dubinsky,
1981), or both (Zvalinskii ~~. , 1980).
In general corals
growing in high light environments have greater values for P~
(expressed as oxygen produced per hour per mg chlorophyll-a, Ik'
and R than do corals growing in low light environments. Conversely
corals growing in low light environments have greater values for a
and are thus potentially more effective photosynthetically in dim
light than are their conspecifics from high light environments.
The relationships between the seasonal average values for
these photokinetic parameters and light intensity (photosynthetic
photon flux density, PPFD, 400-700 nm), can be described by the
general equation,
(s lope) InT + In Xl
(3 )
where X is a photokinetic parameter, T is the function of PPFD
transmitted to the collection depth, and In Xl is the y-intercept
(Chalker ~~, 1983). The differences between summer and winter
values for the photokinetic parameters are strictly a function of
light intensity. Thus, equation (1) is valid for both summer and
winter if T is redefined to the fraction of light reaching each
depth relative to light just below the surface during a cloudless
summer solstice (Chalker and Dunlap, 1983a). The possibility of
hysteresis in the approach to these seasonal extremes, such as that
observed for phytoplankton (Steemann Nielsen and Hansen, 1961), has
not yet been tested.
This communication uses these mathematical descriptions of
coral photoadaptation to simulate light saturation curves for the
reef-building coral Acropora granulosa growing at various depths on
Davies Reef, Great Barrier Reef during r:ecember and June.
Diel
curves are also constructed and integrated to estimate total diel
In suitable habitats, reef-building corals are abundant at all
depths within the photic zone or approximately from 100% to 1% of
the surface light intensity. It is not surprising that
photosynthetic photoadaptations have been observed in comparisons
of P-I curves for corals growing at different depths (Kawaguti,
1937; Wethey and Porter, 1976a,b; Davies, 1977,1980), in light and
shade environments at the same depth (Falkowski and Dubinsky,
1981), or both (Zvalinskii ~~. , 1980).
In general corals
growing in high light environments have greater values for P~
(expressed as oxygen produced per hour per mg chlorophyll-a, Ik'
and R than do corals growing in low light environments. Conversely
corals growing in low light environments have greater values for a
and are thus potentially more effective photosynthetically in dim
light than are their conspecifics from high light environments.
The relationships between the seasonal average values for
these photokinetic parameters and light intensity (photosynthetic
photon flux density, PPFD, 400-700 nm), can be described by the
general equation,
(s lope) InT + In Xl
(3 )
where X is a photokinetic parameter, T is the function of PPFD
transmitted to the collection depth, and In Xl is the y-intercept
(Chalker ~~, 1983). The differences between summer and winter
values for the photokinetic parameters are strictly a function of
light intensity. Thus, equation (1) is valid for both summer and
winter if T is redefined to the fraction of light reaching each
depth relative to light just below the surface during a cloudless
summer solstice (Chalker and Dunlap, 1983a). The possibility of
hysteresis in the approach to these seasonal extremes, such as that
observed for phytoplankton (Steemann Nielsen and Hansen, 1961), has
not yet been tested.
This communication uses these mathematical descriptions of
coral photoadaptation to simulate light saturation curves for the
reef-building coral Acropora granulosa growing at various depths on
Davies Reef, Great Barrier Reef during r:ecember and June.
Diel
curves are also constructed and integrated to estimate total diel