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Horrill et al. 2000 reviewed the coral reefs of northern Tanzania with respect to distribution, condition, physical and chemical characteristics as well as socio-economic and management issues; while Darwall et al. 2000
reviewed similar aspects for southern Tanzania.
Muhando 1999 reviewed the extent of reef damage and socio-economic impacts caused by the 1998 coral bleaching event and discussed the subsequent recovery of reefs.
Guard and Masaiganah 1997 reviewed the findings of the marine biological and resource use surveys which were conducted by Frontier-Tanzania in southern Tanzania, discussing the extent of damage by dynamite fishing,
the intensity of its use, geographical variations Kilwa, Lindi and Mtwara and recommended possible solutions.
Wagner 1997, 1998a reviewed impact of various types of fishing on coral reefs, while Wagner 1998b, 1999 reviewed the importance, threats, conservation and restoration of coral reefs.
4.3 Research methodology
This section pertains to baseline, observational, experimental and applied studies, but of course, not review studies.
4.3.1 Sampling AspectsParameters
Most of the earlier studies, such as Hamilton 1975 and Hamilton and Brakel 1984 were qualitative, only recording the presence and absence of coral species and their zonation and assemblage patterns on reefs. Little
attention was paid to other biotic or abiotic aspects of the coral reef ecosystems.
More recent studies have reported quantitative, or at least quasi-quantitative data, most commonly giving percent cover of hard coral, the percentage of hard coral that is alive or dead, and sometimes the percent cover of each
species. Moreover, these studies have also characterised the coral reef ecosystem by reporting percent cover of other types of biological cover soft coral, algae, etc., percent cover of various non-living substrate types rock,
sand, etc., invertebrate counts, fish density, and measurements of abiotic factors such as temperature, salinity, turbidity, etc. Experimental studies have determined the growth rates of coral transplants Franklin et al, 1998;
Allen, 1998; Wagner et al., 2000a,b or the recruitment rates of coral larvae Nzali et al., 1998; Nzali, 1999. While the Institute of Marine Sciences has not yet published it’s annual monitoring report, it is important to note
that permanent monitoring has started of a number of sites in Tanzania.
4.3.2 Instrumentation and Techniques of Sampling and Collecting Data
Baseline or observational studies on the condition and health of coral reef ecosystems has generally fallen into two categories: rapid assessment techniques and intensive, rigorous sampling.
Rapid assessment techniques, such as the surveys done by Frontier-Tanzania Darwall et al., 1994; Choiseul and Darwall, 1996; Darwall, 1996a,b; Darwall and Choiseul, 1996; Darwall et al., 1996a,b,c,d; Darwall et al., 1997;
Hanaphy and Muller, 1997; Guard, 1998; Guard et al., 1998a,b,c involve swimming, while SCUBA diving or snorkelling, for a fixed time interval or an estimated distance and recording aspects such as percent biocover,
percent substrate type, fish density and invertebrate density. The survey can also be done while the diver is pulled behind a boat while holding onto a manta board, i.e., the Manta Tow Survey Horrill, 1995; Wagner et al., 2000b.
These techniques are very useful in that a lot of information can be gathered over a large area in a relatively short period of time. The disadvantages are that, though they are to quite an extent repeatable, they are somewhat
subjective, so the reliability of repeated measurements depends largely on the uniformity of training.
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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
