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RELATIONSHIP BETWEEN CORAL DIVERSITY AND DIVING PRESSURE AND FACTORS AFFECTING DIVER COLLISION RATES

Introduction

The number of people learning to dive in recent years has dramatically increased however with this increase in divers concern has arisen for the impact that diving may have on the coral reefs. Heavily dived areas have become degraded and so there is a need by travel companies to search for new pristine sites and thus degrading new areas otherwise untouched.

Coral reefs are subject to a range of natural and anthropogenic disturbances that affect the local diversity and abundance of marine organisms. Effects of hurricanes, predator outbreaks, coral bleaching and extractive human activities such as fishing, mining and coastal reclamation have combined to cause an alarming decline in the condition of coral reefs in many parts of the world (Birkeland, 1997). In addition to these, the increase in diving will also be accumulating to the damage already present on some reefs.

Scuba divers may unintentionally damage stony corals and other benthic reef organisms by breaking their skeletons and abrading their tissues (Hawkins and Roberts, 1992). Once damaged, coral may be more susceptible to disease and algal competitors, in addition serious damage occurs when misplaced boat anchors scar the reef (Hawkins and Roberts, 1994).

In the sites studied around Hoga Island, South East Sulawesi mooring buoys have been implanted to help prevent the further damage to the reefs by the use of anchors. The number of divers present in the Wakatobi Marine Park still remains at a very low intensity, however an increase in the number of divers and high intensity diving at some of the sites will impact these reef habitats causing some degree of degradation.

Aims

To understand the relationship between coral diversity and sites with variable number of divers.
To understand the factors affecting the diver collisions with the reef.
To understand the impacts of different forms of education packages and their effectiveness.

Objectives

Using 3 sites; a heavily dived site, a second site with an intermediate number of divers and a third site with a relatively low number of divers. The Line Intercept Transect method will be used at different depths to assess the coral diversity.
Observing other divers and recording their activity, what part of their body or equipment contacted the reef and with what it contacted. Other conditions and factors are also considered.
The implementing of different forms of education packages from no briefing, a video and a lecture and the number of collisions recorded to see if any effect has been achieved.

Methodology

The Line Intercept Transect method will be used at 3 different sites with varying number of divers. A heavily dived site, a site with an intermediate number of divers and a relatively low level dived site will each have four transect lines of 100m recorded. Two transects will be completed at a depth of 5m and two at a depth of 10m. The transect line will record all types of hard corals, soft corals, rock, dead coral, sand and their growth forms where appropriate. The measurement that each different substratum finished will be recorded and data will be collected from the 0-20m, 40-60m, 80-100m distances from the buoy line, at both depths in opposite directions.

Anonymous observers will also be studying the behaviour of divers in the water and also recording details of their experience, age, current, visibility, group size, depth, reef topography, activity, gender, camera use and whether a group is guided. Initially no form of briefing will be used as a control. A video form of an education package about diver damage will be used for both new and more experienced divers and then a lecture given about diver damage will be given again to both new divers and more experienced divers. With each dive observations are recorded within 10 minute segments and observers record the number of times a diver contacts the reef and whether the contact was by fin, hand, kit or other part of the body, also the type of substratum and growth form needs to be recorded.

Preliminary Results

The observations of diver contacts with the reef have produced a mean number of contacts of 0.69 per 10 minute segment with a total of 504 contacts with the reef or surrounding environment from over 700 divers observed in total. Over 44% of all contacts with the reefs were using a hand and were generally a voluntary contact using one finger to push away from the reef. Involuntary contacts were caused by fins (38%), Kit (10%) and body (8%).

The education packages used have shown to be effective, the lecture format causing the greatest significant decrease in the number of contacts.

The Line Intercept transects for each site has not shown any difference in diversity relating to the number of divers present this therefore indicates that the number of divers at present is not causing an impact on the reefs. However the sites chosen for dive training (therefore heavily dived) were chosen due to the damage already present caused by other means i.e. bomb fishing, which may have affected these results.

Report

A dissertation entitled Relationship between coral diversity and diving pressure and factors affecting reef collision rates by divers will be produced by Michelle Chapman, University of Southampton by March 2003

References

Birkeland, C. Editor (1997) Life and death of coral reefs, Chapman and Hall, New York, USA.

Hawkins, J. P. and Roberts, C. M. (1992) Effects of recreational scuba diving on fore reef slope communities of coral reefs, Biological Conservation, 62, 171-178

Hawkins, J. P. and Roberts, C. M. (1994) The growth of coastal tourism in the Red Sea: present and possible future effects on coral reefs, Ambio 23, 503-508,