Dr. Mebrahtu Ateweberhan is a visiting research fellow at Warwick University working on climate change impacts on Western Indian Ocean coral reef ecosystems and coastal communities. He has lived in Kenya and worked with WCS on the interaction between closed area management and bleaching. He was a lecturer at the University of Asmara, Eritrea where he taught courses in Marine Botany, Marine Ecology and Coral Reef Ecology. He has a wide interest and worked on the following:
Taxonomy and biogeography
• Taxonomy of Red Sea and Western Indian Ocean flora, including macroalgae, seagrass, and mangroves.
• Scale and structure of coral reef diversity distributions.
Macroalgal and coral population and coral reef community ecology
• Population and module dynamics of benthic macroalgae in relation to monsoon driven seasonality.
• Population changes in corals in relation to climate change.
• Algal-coral-herbivore interactions.
Ecological effects of climate change and management on coral reefs
• Large-scale spatial variation in coral bleaching and mortality and their relationships to historical SST variations
• The interaction between coral bleaching and closed area management
• Integration of social and ecological aspects in combating climate change impacts on coral reefs.
Climate change and coastal communities
• Investigation of adaptation of coastal communities to climate change through integrated social-ecological studies
Recent studies in the Caribbean and the Pacific and Eastern Indian Ocean regions indicated significant long-term region wide changes in coral cover due to many interacting stress factors. The western Indian Ocean region (WIO) remains one of the main reef regions where little is known about the timing, rate and spatial variability of change in coral cover.
We compiled a cover database based on published and unpublished data for ~2000 site-time combinations gathered between 1958 and 2005. Investigation of the spatio-temporal patterns indicated that the 1998 ENSO was the single most important factor in influencing temporal change in coral cover in WIO and resulted in a ‘stepped change’. Analysis of frequency distribution indicated that median coral cover was 38.8% before 1998, 18.13% immediately after the 1998 ENSO and 28.13% in 2001-2005. Cover and latitude correlated significantly immediately after the 1998 ENSO, but not after 2001. Before 1998, highest cover was observed in the central region while after the 1998 ENSO highest cover was in the southern region. The change in cover due to the 1998 ENSO event strongly correlated with the background water temperature, areas of low temperature variability suffering the highest.
We tested the abilities of three variations of a thermal threshold and one multivariate environmental stress model to predict coral cover. Field data were tested against 1) vulnerability indices from a multivariate stress model based on 11 environmental variables, 2) estimates of time until the current summer temperature threshold becomes the mean summer condition, 3) the Cumulative Thermal Stress for the full satellite record, and 4) the 1998 Annual Thermal Stress. The multivariate stress model fit reasonably with the post-1998 cover and susceptibility of the coral community (R2 = 0.42 and 0.25, respectively). Temperature threshold models had poor fits for cover and susceptibility and only the 1998 Annual Thermal Stress had significant predictive power, likely related to impacts from the severe thermal event of that year. We conclude that the ecosystem response of coral reefs to climate disturbances and global warming predictions is more complex than predicted by models based on cumulative temperature anomalies and thresholds and this implies a heterogeneous response to climate warming.