Growth rate of coral reef sponges near Discovery Bay Jamaica after Hurricane Allen

Full description

In February 1986, specimens of five massive sponge species (Pseudoceratina crassa, Ircinia felix, Verongula ardis, Smenospongia aurea and Agelas dispar) were collected from 20 m depth, approximately 1 km to the west of the Discovery Bay Marine Laboratory in Jamaica. The site was covered by a dense bed of Acropora rubble in excess of half a meter thick, which had accumulated during Hurricane Allen and contained numerous small sponges and coral colonies growing on pieces of the rubble.Regular-shaped animals (presumably derived from a single larva), which were attached to rubble and without obvious signs of predation damage were chosen. The sponges were weighed after draining for approximately 20 seconds and the volume measured by displacement in water. Estimates of dry weight were made on 5 individuals of each species after drying for 36 hours at 80°C.The size-class structure of the Pseudoceratina crassa population was estimated using the MIX program, which is an interactive program used to fit distributions to grouped data by maximum likelihood estimation. For Pseudoceratina crassa, it was assumed that there were five size groupings representing the recruitment from five annual spawning events between Hurricane Allen (August 1980) and the date of collection. The mean size of sponges in each size-class was determined from the significant fit obtained to the size-frequency data with the MIX program. These mean values for each size-class were analyzed using a least squares regression to provide an exponential growth model (Wt = ae^alpha t) from which the relative growth rate alpha was estimated.Growth rates for the other four sponge species could not be obtained by the same method due to the limited number of specimens. Growth rate approximations for these species were derived using the growth model from Pseudoceratina crassa, assuming that the average size at 50 days after spawning was the same for all species. Dates for spawning of these species were extracted from the literature.
Hurricane Allen passed within 50 km of the north coast of Jamaica on 6 August 1980. Large seas generated by winds in excess of 250 km per hour caused extensive damage to the coral reefs in the vicinity of the Discovery Bay Marine Laboratory.

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Maintenance and Update Frequency: notPlanned

Statement: Statement: The reliability of growth rate estimates depends on several assumptions:(i) All sponges in the region surveyed were destroyed by the hurricane. The specimens collected originated from newly settled, individual larvae produced by undamaged populations from deeper water;(ii) The individuals collected, particularly the large ones, originated from single larvae;(iii) The sponge species examined produce recognizable size classes which can be related to annual or semiannual spawning events;(iv) The largest sponges resulted from larvae which settled out within the first year after Hurricane Allen.The MIX program used to estimate the size-class structure of Pseudoceratina crassa is described in: Macdonald PDM, and Pitcher TJ (1979) Age-groups from size-frequency data: a versatile and efficient method of analyzing distribution mixtures. J. Fish. Res. Board Can. 36:987-1001.Macdonald PDM and Green PEJ (1985) User's guide to program MIX: an interactive program for fitting mixtures of distributions. Ichthus Data Systems, Ontario, Canada. 28 pp.The program has been used effectively in the analysis of fisheries size-frequency data where the groups represent successive year classes.Dates for spawning of sponges were derived from:Reiswig HM (1983) 1. Porifera. Pp. 1-21 in Spermatogenesis and Sperm Function, KG and Adiyodi RG (eds). John Wiley & Sons, New York.Hoppe WF (1988) Reproductive patterns in three species of large coral reef sponges. Coral Reefs 7: 45-50.

Notes

Credit
Wilkinson, Clive R, Dr (Principal Investigator)