Coral Reef Communities in Kenya: Status, Patterns and Resilience

Abstract

Coral reefs are important ecosystems providing ecological and social services but are declining at an alarming rate globally with climate change being one of the biggest threats. Understanding the resilience-enhancing properties of these ecosystems will help focus management intervention that support the persistence of these ecosystems amid climatic disturbances. This thesis determines the spatial and temporal patterns of coral reef communities and how this influences the resilience of coral communities. First, I determine the spatial pattern of benthic coral reef communities in Kenya using rapid underwater assessments and find that there is a spatial heterogeneity in the composition of benthic communities across different reef habitats. This pattern is tied into two levels, there is a broad latitudinal gradient in benthic community composition that separates north and south geographic zones. This latitudinal gradient is further compounded by a more complex habitat-level pattern with a highly heterogenous benthic community in the north. Second, I determine the demographic changes in coral communities by comparing with past data and classify their responses into three groups reflecting ongoing recovery patterns in 2015/16 from 2008/9 and the initial bleaching in 1998. ‘Group I’- coral community with increasing colony sizes and numbers representing potentially high recruitment and growth; ‘Group II’- increasing colony sizes but decreasing numbers suggesting potentially low recruitment but good growth; ‘Group III’- decrease in density with no change/decrease in area representing declining populations with low recruitment and low ability to grow. The temporal pattern is influenced by regional differences. Thirdly, I determine the spatial pattern in resilience of coral communities by applying a bivariate analysis of resistance and recovery properties of resilience from bleaching disturbance. Using some of the variables that were analysed in the previous parts of the study as indicators, I quantify the resistance and recovery potential of reefs along the Kenyan coast. Results show that resistance and recovery potential of coral communities is highly influenced by habitat factors with depth, exposure to oceanic waves and reef type having a significant role in structuring this pattern. Resistant potential is higher in patch reefs that are deep and exposed to oceanic waves. Recovery potential is higher in channel reefs that are shallow and exposed to oceanic waves. Finally, discussion is based on how these findings are important in providing information about the current status of coral reef communities in Kenya, their recovery trajectory from previous bleaching disturbances and their resistance and recovery potential. I suggest that re-designing and creating new MPA networks should include replicates of representative habitats with high resistance and recovery potential to bleaching in order to spread the risk of coral loss from other localized disturbance including failures in management.