Aspects of the life history of the soft coral Efflatounaria sp. on Davies Reef, Great Barrier Reef

Full description

Stereophotography was used to study life history characteristics of Efflatounaria sp. at two sites at Davies Reef on the Great Barrier Reef, between December 1980 and June 1982. Site 1 was located on a patch reef about 200 m long on the leeward margin of the lagoon which had a comparatively high density of Efflatounaria sp.. Site 2 was located on a similar patch reef approximately 1 km away, within the lagoon but close to the leeward margin and had a lower density of Efflatounaria sp..Plots (1 m²) were established at about 5 m and 10 m below low water datum on hard substrate. At Site 1, plots were set up with both high densities (much greater than 50 colonies per square metre) and low densities (less than 20 colonies per square metres) of Efflatounaria sp.. At Site 2 only low density plots could be established. In addition, 'empty' plots (1 m² and 9 m²) were set up at 10 m depth at both sites. At Site 1, all Efflatounaria sp. colonies were completely removed from these plots using a knife. At Site 2, these plots were originally devoid of the species. Two replicate were established for each of the above treatments.Plots were photographed at intervals of about 2 months from December 1980 to June 1982, using twin Nikonos cameras and flashes mounted on a 105 em high frame constructed of aluminium and PVC piping. Four pairs of centrally overlapping photographs were taken of each square metre, each pair showing an area 70 x 60 cm. Using a stereoscope, maps were drawn for each plot recording the continued existence, appearance or disappearance of individual colonies and stolons. The precise numbers of colonies and stolons in dense clumps and the presence of very small colonies (less than 2 cm across) were checked by visual inspection underwater. Gonad development was also monitored following collection of approximately 40 colonies at 5-10 m from Site 1, at monthly intervals (more frequently in early summer). Reproductive condition was assessed by dissection and from histological sections. Additional field observations were made in summer 1981, principally at Site 1.
In this study, vegetative propagation, natality and mortality rates, and some aspects of sexual reproduction in the soft coral, Efflatounaria sp. were investigated, to determine characteristics of the species' life history and possible reasons for its great abundance in some areas.
In the xeniid genus Efflatounaria, vegetative propagation by means of stolon-like outgrowths occurs. Stolons usually arise from near the base of a branch or from the colony stalk. Sometimes series of several daughter colonies are formed, interlinked by straight or divided stolons. The stolons may bear polyps and are then usually attached to the substrate throughout their length.

Lineage

Maintenance and Update Frequency: notPlanned

Notes

Credit
Dinesen, Zena D, Dr (Principal Investigator)