Browsing by Author "Rushingisha, George"

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    Modelling coral-corallimorpharia interaction under varying anthropogenic inputs along the coast of Tanzania
    (University of Dar es Salaam,, 2012) Rushingisha, George
    Coral reefs are valuable resources for humanity, but are increasingly threatened by natural and anthropogenic stresses. The increased corallimorpharian abundance on reefs located close to urban centers is alarming as it appears to outcompete and inhibit recruitment of corals. This study investigated the interaction between corals and corallimorpharians under varying anthropogenic inputs using observational, experimental and modelling approaches. The Line Intercept Transect method (LIT) was used to determine changes on corals, corallimorpharians, macro-algae, turf-algae and coral rubble and the changes were correlated to (a) water visibility (b) phosphate and (c) nitrate concentrations. Nutrients and iron were enriched within Porites and Rhodactis rhodostoma interactin plots. A cellular automata (CA) model was applied to investigate the interaction between corals and corallimorpharians under a nutrient gradient. Results indicated no significant changes on corals, corallimorpharians, turf-algae and coral rubble covers during the study period. Porites and Galaxea genera were found to be susceptible and not susceptible to corallimorpharians overgrowth, respectively. Corallimorpharians cover correlated positively to phosphate and nitrate concentrations but negatively to water visibility. The experimental results indicated higher R. rhodostoma growth rate in nutrient enriched plots (1.7cm/month) than controls with and without iron nail (0.5cm/month). The model showed that corallimorpharians spread was faster and their cover was higher on high nutrient zone. The study suggests nutrient as the major factor facilitating corallimorpharians overgrowth on corals. Therefore, coexistence between corals and corallimorpharians is only possible under low nutrient conditions.