Growth of the two most common Halimeda species (H. copiosa and H. opuntia) was studied at 4 sites on Davies Reef over 6 tagging periods between February 1981 and February 1982. Comparative data was collected from Myrmidon Reef for one tagging period (November 1981 to January 1982).
A total of 1685 branch tips were tagged over the period of a year during visits to the reef at approximately 2-month intervals. New growth was recorded by detailed drawings mid-way and at the end of the period. If growth was too complex to record in the field, those samples were collected and taken back to the laboratory; new batches were tagged as replacements. The laboratory samples were photocopied, dried and weighed, and the total surface area measured with a Licor LI-3000 area meter.
Variables recorded were: days, number of samples, time of year (Feb/Mar, Apr/May, Jun/Aug, Aug/Oct, Oct/Dec, Dec/Feb). Halimeda community habitat variables were: hole, bommie, leeward slope, windward slope.
Rates were calculated for number of new segments per day. Rates of production were calculated in two ways based on (1) the number of branch tips per unit biomass and the rate of new segment production; and (2) the rate of loss of tagged branches in conjunction with rates of new segment production. Rates of contribution of Halimeda debris to sediment composition were also calculated.