Long term changes of Suva Reef flat communities from conventional in situ survey and remote sensing methods

Abstract

This work is concerned with the combined use of conventionally-gathered data and remote sensing methods to study the communities of Suva Reef, Fiji. A principal objective was to observe coral reef processes that could not be studied effectively by either approach individually. The in situ surveys have provided detailed information on reef community dynamics at a small scale while the airborne images have been able to reveal the longer term general patterns.The results of in situ surveys show massive changes to the reef substratum caused by Echinometra mathaei excavations. The disturbance cause by E. mathaei was associated with increases of turf algae. Four decades of habitat changes were documented from airborne images. The magnitude and spatial extent of these changes were related to likely causes. In particular, the long term patterns of spatial changes of seagrass beds revealed that there were oscillations in the regrowth and losses. Seagrass beds extended towards the lagoon in some years and regressed in others.Other disturbances have also made significant contributions in shaping community structure of Suva reef flat between 1945 to 1991. Major causes of disturbances were tsunami and cyclone damage, flood damage, Acanthaster planci predation and effects of human activities. Tsunamis have probably caused more damage to the structure of the reef than any other disturbance occurring between 1945 and 1990.This investigation has demonstrated the effective of the combined observational approach in improving our ability to interpret the long term significance of reef changes. The understanding arising from the study will be able to underpin the development of scientically based plans for conservation and management of reefs.</p