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GROWTH AND RECRUITMENT RATES OF MASSIVE CORALS
Introduction
Sites in the Hoga island area have different amounts of sediment and damage and percentage cover of coral. There has been no work in this area concerning growth and recruitment rates of massive corals previous to this report. The purpose of the study is to assess the factors which affect the recruitment massive corals, in order to do this sedimentation data will be collected, coral cover will be analysed and events in history such as earthquakes and tsunamis correlated with date of recruitment.
Objectives
The aim of the project is to understand the factors affecting growth and recruitment dates of massive corals by measuring surface area and using published data on growth rates and a polynomial function to find the date the coral was recruited. The degree of sedimentation between the three sites will be compared.
Methodology
Transects of 10m were laid at 3 depths, 5m,10m,15m and at the reef crest at the Hoga and Kaledupa reef sites each transect was replicated 3 times. Transects of 10m were laid at 5m, 10m and the reef crest, due to depth restrictions there was no transect at 15m all transects were replicated 3 times. An underwater visual census was carried out on massive corals within 1 metre either side of the transect line. The corals were identified down to family level and the diameter and 90 degrees to the diameter were measured in cm. Each transect laid was filmed with an underwater digital video camera. The film was then analysed in the lab to assess percentage cover of massive corals, soft coral, sponge, branching coral and dead coral. Sediment traps were laid down at 5m, 10m and 15m in replicates of 3 at each of the 3 sites. The traps were left at each site for 5 days. The traps were filtered and the sediment dried and weighed to compare the 3 sites.
Analysis of results
To analyse massive coral diversity at each site chi squared test can be used to test for a statistical difference between the 3 sires. Depth at each site can also be compared to see whether this affects the abundance of massive coral. A plot of coral recruitment dates can be used to determine whether there is any correlation with major ecological events or bomb fishing damage.
Expected results
Initial results show that there is no difference in when the massive corals were recruited at any of the three sites and ecological events did not have a major impact on the recruitment of massive corals. However there was far less diversity at the sites damaged by sedimentation and bombs than at the pristine site. At the sediment damaged site it was noted that massive corals seemed to be the only successful form, there was little or no branching and tabular coral. The bomb-damaged site had far fewer massive corals however coral diversity was not greatly affected.
Outputs
A report entitled 'Factors affecting recruitment of massive corals in three areas of the Wakatobi Marine National Park will be produced by Jennifer Rooke, University of Portsmouth by May 2001.