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Scleractinian corals are the key contributors to coral reef formation.Therefore,its health is of high ecological concern.Nutrient enrichment has long been considered one of the major causes of coral reef degradation around the world,where high levels of nutrients lead to rapid growth of macroalgae and benthic filter-feeders,such as sponges and bryozoans,which would outcompete corals for space,in turn affecting coral larval settlement and recruitment.Eutrophication may also increase the growth of faster-growing macroalgae,resulting in shading of the corals and consequent reduction of photosynthesis by their endosymbiotic zooxanthellae.However,recent in situ studies suggest that nutrient enrichment from fish farms can actually enhance the growth and reproductive potential of scleractinian corals in nearby areas.In Hong Kong,wastewater discharge from the Pearl River Estuary is a major reason for relatively high and increasing nutrient levels.Local fish farms may also be another source of nutrients to coral areas.HKSAR government data show an increase in nitrogen levels (i.e.nitrate) over the past two decades.At present,the effect of high nutrient levels on growth rates of local scleractinian corals is not known,since it would depend on the proportion of autotrophy versus heterotrophy of local corals,which has not yet been determined.This study will establish the mode of nutrition of selected coral species,and thus investigate whether elevated nutrient levels will promote or be detrimental to coral growth rates.