Detecting and visualizing potential multiple coral reef regimes in Doreri Bay, Manokwari Regency, Indonesia

Abstract

Impact of local pressures in synergy with effects of global climate change can functionally cause damage to coral reefs and lead to changes in benthic structure often called regime shift. There is an urgent need to anticipate the regime shift as a result of the loss of coral reef resilience. This research aimed to detect and visualize the potential of multiple coral reef regimes in Doreri Bay, Manokwari Regency, Indonesia. Benthic cover data collected by applying underwater photo transect (UPT) method at 5 observation stations. Each station consists of 5-7 sampling sites, bringing the total number of 30 sites. To obtain quantitative data on benthic habitat, data analysis performed on each photo frame by selecting a number of 30 random samples. Descriptive statistics (mean ± SE) were used to compare the cover of six benthic categories within the study area and between stations. In order to detect, visualize and define potential multiple regimes, a combination of exploratory ordination methods was applied, including calculation of the phase shift index (PSI) and multimodality examination, correlation-based PCA, hierarchical cluster analysis, and K-means clustering. The mean percentage of hard coral cover (HC) is the highest compared to other benthic categories at nearly all stations, followed by the abiotic cover (AB) and dead coral cover (DC) respectively. PSI calculation and multimodality test displayed a normal distribution, indicated an absence of multiple regimes. However, the combination of correlation-based PCA and Clustering analysis approach highlighted the existence of three primary reef regimes dominated by live coral, algae and abiotic/dead coral.