77
were obtained from the Nautical Almanac (Her Majesty's Nautical
Almanac Office, 1980). Values for Im at each depth were obtained
by multiplying surface PPFD at local solar noon by the measured
light transmittance of the water at each depth. EStimated ~situ
rates of net photosynthesis were calculated by substituting
equations (4-7) into equation (I), to yield
P~
P~l exp (clrt!' }tanh (ImTsin( lTH/D) / (I kl exp( alrt!') } }-R l exp( dIrt!'}
(8 )
Light saturation curves for gross photosynthesis were simulated by
the equation,
(9 )
A single equation for estimating instantaneous rates of gross
photosynthesis was obtained by combining equations (4,5,7 and 9),
P g
T
P~l exp (clrt!') tanh (I mT sin (lTH/D}/(I kl exp (dlrt!')}).
(10 )
Estimated diel JE. situ rates for primary production were calculated
by integrating equation (10) for the length of the day using a
Simpson's rule approximation (Hamming, 1971). Es timated JE. situ
rates of respiration were calculated by multiplying hourly rates,
from equation (6), by twenty-four.
RESULTS AND DISCUSSION
Using equations (1,4,5, and 6) and parameters calculated from
the data of Chalker and Dunlap (1983a), light saturation curves for
photosynthesis were calculated for 1:... granulosa growing at depths
from 1 to 50 m on Davies Reef in December (figure l) and June
(figure 2). In each figure, P~ (normalized per mg protein) and a