Sampling Frequency and PeriodTime of Collection Data Analysis Methods and Procedures

105 Intensive, rigorous techniques include the use of line intercept transects, belt transects, point-based sampling, permanent quadrats, and permanent photoquadrats. These techniques give fairly accurate data on the percentage of each type of biocover, each species of coral and each non-living substrate type. Moreover, repeated measurements can give reasonably consistent results, even if done by different people who never trained together. The disadvantage of these methods is that they take a lot of time to cover a small area. Generally, to get both extensive and accurate information about a system of reefs, both rapid assessment and intensive sampling techniques should be applied and the results synthesised. Another way to cover a fairly large area and produce reasonably accurate results is by underwater photography. Lindahl 1998 took random photographs of a reef which he later analysed by point sampling on slide projections Lindahl, 1998. Wagner et al. 2000b took underwater photographs systematically and later analysed them for percent cover of life form and substrate categories by placing a mini-quadrat over them. Photography has also often been used for descriptive and taxonomic work. Hamilton 1975 presented numerous photographs of many species of corals, providing a good record or reference for their identification. Studies on biological aspects of coral reefs have often been accompanied by recording measurements of abiotic factors such as seawater temperature thermometer or temperature logger, water transparency Secchi disc, sedimentation rates sedimentation traps tied onto fixed steel rods, reef structural complexity Ohman et al., 1999 and meteorological factors. Socio-economic aspects of environmental issues and the utilisation of coral reefs have been studied by standardised interviews Andersson, 1998; Wagner et al., 1999, informal interviews and participatory observation Solandt and Ball, 1999, as well as by Participatory Rural Appraisal PRA, including transect walks, participatory resource mapping, and focus group discussions Wagner et al., 1999.

4.3.2 Sampling Frequency and PeriodTime of Collection

Temporal aspects of different studies have been very variable. Nzali et al. 1998 examined clay tiles for coral recruits every 8 weeks for 12 months. Lindahl 1998, in his experimental study, transplanted corals in November 1995 and took measurements in October 1996 and October 1997, the entire study period being 23 months. Ohman et al . 1999 conducted an experiment over a period of 3 years, taking measurements after the second and third years. Many other studies, particularly baseline studies have just been conducted once, irrespective of season.

4.3.3 Data Analysis Methods and Procedures

Data analysis has varied, depending upon the number of factors involved, the number of groups compared, the nature of the data normality, homogeneity of samples, etc., and the hypotheses tested. Nzali et al. 1998 compared coral recruits at two sites and on upper and lower sides of tiles using the non- parametric Mann-Whitney U test, while correlations between environmental factors were tested using the non- parametric Spearman rank correlation coefficient. In the Tutia reef studies, Lindahl 1998 applied orthogonal three-way ANOVA with three fixed factors. Ohman et al . 1999 analysed changes in abundance and diversity of fish over time using a pairwise t test and related reef structural complexity to fish abundance using Spearman rank correlation. They applied the ANOSIM permutation test analysis of similarities to test for significant differences in fish community composition before and after bleaching. 106 Wagner et al. 2000a used different tests for different aspects of their study, including the Mann-Whitney U test, two-sample t test, χ 2 test, contingency tables, and the Kruskal-Wallis test. Wagner et al. 2000b used the paired- sample t test, the Wilcoxon paired-sample test signed rank test, two-sample t test, and the Mann-Whitney U test.

4.4 Reliability, quality and usefulness of data information