Ecology of Black Coral — G rigg 
245 
Fig. 1. Large colony of A. grandis, at 58 meters, off Lahaina, Maui (Station 9). It is approximately 3 Vi 
meters across and 2 meters high. Photo by Ron Church. 
while the two cells were exposed to full sunlight. 
Then one cell was lowered to the bottom and 
the difference in electrical potential was meas- 
ured with the galvanometer. This value can be 
converted to percent surface light or to gm 
cal. cm -2 (24 hr)' 1 , and plotted against depth 
(Fig. 6). 
These measurements were taken at an hour 
when the sun was at maximum altitude on days 
when turbidity was at a minimum. Thus it was 
attempted to measure the maximum penetration 
of light for a particular depth. 
turbidity: Samples of water were collected 
from various stations and analyzed with a Tyn- 
dall meter so that turbidity values could be com- 
pared. Since only relative values were required, 
it was not necessary to calibrate the Tyndall 
meter. 
oxygen CONCENTRATION: Dissolved oxygen 
was measured by the Modified Winkler Method 
(Hydrographic Office Pub. No. 607). 
SALINITY: The Knudsen Method was em- 
ployed to measure chlorinity, which is easily 
converted to salinity by the formula: Salinity = 
0.03 + (1.805 X chlorinity) (Hydrographic Of- 
fice Pub. No. 607). 
TEMPERATURE: Temperature as a function of 
depth was recorded by using a bathythermo- 
graph. Data were also collected with a simple 
110° Celsius thermometer carried to the bottom 
by a diver. Temperature increase due to hydro- 
static pressure was assumed to be negligible and 
thus was not taken into account. 
substrate: Portions of the substrate were 
chiseled with an axe and sledge hammer and 
