Due to climate change and thermo expansion of the sea, rise is occurring. If this occurs the corals will have to increase their growth rate, to stay at a depth that has light readily available to photosynthesise. The rate of sea level rise in the Holocene was thought to be around 20cm per decade (Smith & Buddemeir 1992, Bard et al. 1990, Fairbank 1989). In a recent climate model there are predictions that the sea level will rise by 3-9.7mm per year (IPCC 2007). As different species grow at different rates some corals may not be able to ‘keep up’ with the rise. The slowest growing corals are in areas of lagoon sands and only grow 1mm yr-1 upwards. The fastest growing corals grow at 7mm yr-1 upwards at the reef flat. This is 2.7mm yr-1 slower than the sea level rise. The zooxanthellae will not be able to photosynthesise without the use of light, and therefore the coral will eventually die. The corals that are Unable to keep up with the rise in sea levels will be out competed and a selection process will occur where by branching corals with faster growth rates are selected for.