1. Introduction
2. Materials and Methods
1. Gross measures of erosion
2. Rates of sedimentation
3. Sediment load
4. Nutrient status of waters surrounding Sampela and Kaledupa
5. Growth rates of established Acropora spp. colonies located at the Sampela Wall and Kaledupa control site Recruitment rates of scleractinian corals at the Sampela Wall and Kaledupa control site.
6. Recruitment rates of scleractinian corals at the Sampela Wall and Kaledupa control site
7. Growth rates of newly recruited corals at the Sampela Wall and Kaledupa Control Site.
8. Statistical analyses

3.0. Results

3.1 – 3.8 as above

4.0. Reports.

Introduction

Coral reefs are the most diverse of all marine ecosystems and are home to about a third of all fish species and numerous other marine organisms. Therefore coral reefs can be considered banks of genetic diversity. Coral reefs are also biologically important for several other reasons, for example, they act as protective barriers decreasing wave action which might otherwise erode or impact delicate littoral environments. Also reef derived sediments are important components from many littoral environments e.g. beaches and sub-littoral sand banks.

Despite their obvious biological and economical importance, coral reefs are degrading worldwide and current estimates suggest that approximately 50 % of the worlds reefs have been destroyed or are showing evidence of severe degradation. Natural disturbance events, such as storm damage, are important in maintaining overall community diversity, however additional anthropogenic factors are resulting in accelerated degradation which is not sustainable. Many anthropogenic factors cause reef degradation but probably the most common and therefore the most important is coastal development resulting in the change in water quality. Coral reefs only exist in clear oligotrophic waters and therefore factors that result in reduced light availability or increased nutrient load will affect the community structure of the reef as well as coral growth rates. If growth rates are impaired to an extent where natural erosion is greater than accumulation then the coral reef will eventually disappear which will have major consequences for the coral community and associated habitats.

During 2000 an investigation of the coral community structure was carried out on the Sampela Wall, a site which is impacted by a high water-sediment load. During this investigation the extent of sedimentation and sediment load was quantified. Furthermore, as a direct result of light limitation, it appears that the coral community growth and calcification rates are impaired resulting in a net loss of material from the Sampela Wall. There are particular sites on the Sampela Wall which are more adversely effected than others, where coral rubble is slumping down the reef wall. During this investigation the rate of slumping and the physical characteristics of these coral slips was investigated. Digital photography was used to examine the size of these slips over a time course which will enable predictions to be made about the fate of the Sampela Wall. Finally nutrient samples were taken from surrounding areas to see if the reef would become eutrophicated if it were not light limited. Consequently the aim of this investigations was:

In order that this aim be met the following objectives were set:

1. To examine the slope and rugosity of the Sampela Wall and compare results to a non-impacted coral wall at Kaledupa.
2. To deploy coral rubble trays at the base of coral slips and along the wall at Sampela and Kaledupa control site.
3. To examine the sediment load at different tidal stages in waters around the Sampela Wall and Kaledupa control site.
4. To determine the rates of sedimentation on the Sampela Wall as compared to the Kaledupa control site
5. To take nutrient samples from Sampela Village, Sampela Wall and Kaledupa control site on a high and low tide (3 replications temporally and spatially).

During the investigation the following new objectives were set. Results obtained from these new objectives will not be available until 2002 due to the nature of the investigation:

6. To examine the growth rates of established Acropora spp. colonies located at 10 m depth at the Sampela wall and kaledupa control site.
7. To examine the recruitment rate of all scleractinian coral species at the Sampela Wall and Kaledupa control site
8. To examine the growth rates of newly recruited coral colonies at the Sampela Wall and kaledupa control site

Five vertical transect from 12 m to 2 m over the reef crest were examined from each site. Every 2 m up the transect the slope was assessed by an inclinometer. Rugosity as a measure of topographic complexity was examined at each 2 m station of the vertical transects. To determine rugosity (as a percentage) a chain of known length was laid 90 ⁰ to the transect every 2 m up the transect. The bead-chain was pushed into all crevices along the horizontal section of the reef. The length of the chain was then measured and percentage rugosity calculated by:

Rugosity ( %) = (1-[length of chain in situ / total length of chain]) x 100

Coral rubble trays were deployed at 7 locations along the SampelaWall, 4 at the bottom of coral slips and 3 at the bottom of the wall proper. 3 rubble trays were also deployed at a comparable depth ( ca. 12 m) on the Kaledupa control Wall. The contents of the rubble trays will be examined during April 2002 and July 2002. The contents of the trays will be described fully and measured (length and weight).

Rates of sedimentation was assessed at the Sampela Wall and Kaledupa control site. Sediment traps consisting of 500 ml water bottle plus funnels were located at 3 sites at Sampela and 3 sites at Kaledupa in triplicate. Sediment traps were deployed for 7 days when they were collected and replaced. Three time periods were examined. On return to the Hoga base, sediment samples were filtered through a GF/F filter and the filtrate was discarded but the filter paper plus sediment sample was preserved. On return to the UK samples will be dried overnight at 80 ^oC and weighed. Sub-samples will be analysed on a CHN analyser to characterise the sediments being deposited at the two sites. Further sub-samples will be examined under light microscopes and the particle size determined.

500 m water bottles were used to examine sediment load in waters adjacent to the Sampela Wall and Kaledupa control site. Samples were taken from a depth of 5 m in triplicate and on three occasions corresponding to a low tide period and on three occasions during a high tide period. The water samples were filtered through a GF/F filter (diameter 47 mm) and this pre-weighed filter paper plus sample will be preserved and re-weighed on return to the UK. The difference in weights x 2 will give the sediment load in mg per litre. These values will be compared to Secchi disc readings.

Water samples were taken from three sites: Sampela Village, at 5 m depth on the Sampela Wall and at 5 m at the Kaledupa control site. Samples were filtered and the filtrate preserved for nutrient analyses (nitrate, nitrite, ammonia, silicate and phosphate) back in the UK. Samples were taken on low and high tide on three separate occasions in triplicate.

Acropora colonies were located at a depth of 9 – 15 m at the Sampela Wall and Kaledupa Control site. The length of six branches ( inside measurement from tip to previous branch always on the acute angle) were measured and recorded and each branch was tagged with a plastic label attached to the branch with fine fishing line. Care was taken not to damaged the coral surface. Video footage was taken by Prof. Crabbe (Reading University) and images were validated against actual branch measurements maid to allow measurements of all branches to be made from the video footage. The same branches will be measured during the 2002 season and consequently growth rates will be obtained.

The general method used to determine recruitment rates of scleractinian corals is to establish recruitment-tiles on a frame at 45 ^oC facing the direction of the prevailing currents. Current direction at the Sampela Wall and Kaledupa Control site appears highly variable and therefore rather than single-sided frame a tetrapod array was constructed upon which tiles could be attached to four sides facing north,east, south and west (see fig 1).

Figure 1. Coral recruitment tertrapod array used to examine recruitment rates of scleractinain corals at the Sampela Wall and Kaledupa control site.

On each side of the pyramid, 6 terracotta (15 cm²) tiles were firmly secured. Three of the tiles from each side will be randomly chosen after approximately 1 month and will be removed for microscopic analyses and macro-photography, and replaced with clean tiles. Three pyramids were be located at 5 m depth at both sites and attached to the substratum by 4 30 cm bent rods.

2.8  Growth rates of newly recruited corals at the Sampela Wall and Kaledupa Control Site.

The remaining 3 tiles located on each side on the array will be photographed at the same interval as recruitment tiles are removed, however they will be left in situ to allow continual assessment of growth rates. Measurements of corals will be made in situ and by image analyses.

Analyses of variance will be used to examine differences between sites and poc hoc Tukey test will be used to determine where differences lie. Measurements made for the physical structure of the reef will be grouped according to depth, intervals being 2 m. Relationships between variables will be examined by Pearsons correlation. Shannon-Weinner diversity index will be used to examine scleractinian coral community diversity and cluster analyses using percentage similarity will be used to examine community structural differences between sites and depth.

The rugosity of the Kaledupa Wall varied significantly with depth (F _{2, 30} = 7.48, p < 0.01) with greatest rugosity being found between 12 – 10 m ( 55.04 ± 10.36 %) and the lowest rugosity was determined for the reef flat between 4 – 2 m (40.28 ± 7.85 %) (See Fig 2).There was a significant positive correlation between depth and rugosity ( r = 0.56, p < 0.01, df = 30). This was in contrast to rugosity measurements determined for the Sampela Wall. Once again there was a significant difference with depth (F _{3, 44} = 4.03, p < 0.02), but greatest rugosity was found above 4 m (35.74 ± 8.18 %) and the lowest rugosity was found between 12 and 10 m (24.68 ± 6.28 %) (see Fig 2). There was a significant negative correlation between rugosity and depth at the Sampela Wall ( r = - 0.45, p < 0.01, df = 43). There was no significant difference between rugosity on the reef flats ( 6 – 2 m) at Sampela and Kaledupa, but there was a significant difference at depth (12 – 10 m, p < 0.0001, t-test), with Kaledupa having a rugosity of 2.3 x that of Sampela. There was no significant difference between the slops of the two sites although the Kaledupa Wall has a higher variation in slope angle.

Figure 2. The rugosity (%) of the Kaledupa Wall (empty circles) and the Sampela Wall (full squares) at varying depth categories. Measurements were made on 5 separate transects and results were pooled according to depth.

Five rubble trays were placed at Sampela and three at Kaledupa. To date only course sand and some seagrass blades have accumulated in these baskets. The baskets will be examined during the beginning of October at which time accumulated material will be brought to the surface and analysed. The baskets will be surveys again during April, July and August 2002.

A total of 54 sediment traps were deployed (see Table 1). Sediment samples will be analysed on return to the UK.

Table 1. Site of sediment trap deployment and duration of deployment

54 samples 500 ml samples were collected on three occasions from Sampela Village, Sampela Wall, and at the Kaledupa control site on low and high tide. Samples will be analysed on return to the UK.

54 water samples were collected on three occasions from Sampela Village, Sampela Wall, and at the Kaledupa control site on low and high tide. Samples will be analysed on return to the UK.

3.6 Growth rates of established Acropora spp. colonies located at the Sampela Wall and Kaledupa control site

Three colonies of branching Acropora were tagged and videoed at Sampela and Kaledupa. At the same time as tagging the length of specific branches were measured (see Table 2). The same branches will be measured during October 2001 and April, July and August 2002.

Table 2. Colonies of branched Acropora tagged and measured during 2001

Three recruitment pyramids have been located at the Sampela Wall and Kaledupa control site. In both cases the pyramid arrays with positioned on the reef flat at a depth of 4-5 m and were orientated northwards. Table 3 summaries the location and dates of deployment.

Table 3. Location, depth and date at which recruitment arrays with deployed

Growth rates will be measured after 12 months on tiles attached to the recruitment pyramids.

Data from this study are being incorporated into the following papers:

• Crabbe, J. and Smith, D. J. (2002). Real-time monitoring of reef health and coral recruitment using digital videophotography and computer image analysis and modelling in the Wakatobi Marine National Park, S.E. Sulawesi, Indonesia. Coral Reefs. 21: 242-244.
  
• Crabbe, J. & Smith J.D (In Press) Computer modelling and estimation of  recruitment patterns of non-branching coral colonies at three sites in the Wakatobi Marine Park, S. E. Sulawesi, Indonesia; implications for coral reef conservation.   Computation Biology and Chemistry.
  
• Smith, D. J., Crabbe, J. and Budianto, A. (in prep) The physical and biological characteristics of  a light-limited and non-light-limited reef system within the Wakatobi Marine National Park (SE Sulawesi, Indonesia). Coral Reefs.
  
• Smith, D. J., Corrigan, L. Crabbe, J. Hukom, F. and Budianto, A. (in prep). The importance of Acropora tables in overall coral reef fish diversity. Coral Reefs [expected submission date Jan. 2003].
  

• Smith, D. J.,  Budianto, A. and Hukom, F. (in prep). The scleractinian coral and associated fish community structure of 12 different reef systems within the Wakatobi Marine National Park (SE Sulawesi, Indonesia). Coral reefs [expected submission date March 2003].