The corallite shape of Goniastrea pectinata also changes in relation to light and Ow and Todd (2010), through modeling light capture, showed PCI-32765 order this response to be an adaptive response to the immediate light environment.

Some morphologies, both at colony and corallite level, are believed to encourage sediment-shedding (Lasker, 1980, Rogers, 1983 and Rogers, 1990). Marshall and Orr (1931), after smothering various coral taxa with sand, concluded that corals with large polyps were better at removing sediment than those with small polyps. Small polyps equate to less tissue-distension potential and thus to a reduced ability to remove coarse grains. Stafford-Smith and Ormond (1992) found that active-rejection capability was positively correlated with calyx size and Hodgson (1993) concluded that large corallites and extensible polyps were advantageous in his tests on 50 species of coral. see more Corals that move larger grains tend to have more septa, high relief and numerous septa teeth. The shape of the calyx is also important to sediment-shedding, with V or U floors apparently beneficial for mechanical reasons (Hubbard and Pocock, 1972). Todd et al. (2001) hypothesised that these features in Favia speciosa may be advantageous to this species in Singapore’s sedimented waters. Further, they found that Favia speciosa polyps were significantly larger at their

most sediment-impacted study site ( Todd et al., 2001). Riegl (1995) also found corallum shape to be important while Dodge (1982) found no

clear trend. Gleason (1998) noted green and brown morphs of Porites astreoides had different sediment-shedding abilities even though small-scale morphologies to were very similar. Even intra-colonial variation can have a great effect on sediment removal; for instance, small differences in colony convexity can lead to areas where sediments accumulate and create anoxic conditions ( Stafford-Smith, 1992 and Stafford-Smith, 1993). In the only study to date to specifically examine whether sediment can induce change in coral morphology, Todd et al. (2004b) found a slight increase in rugosity (the height of the wall measured from the outside of the corallite) in fragments exposed to sediment treatment compared with controls (Favia speciosa control = 1.36 mm, sediment treatment = 1.53 mm; Diploastrea heliopora control: 1.40 mm, sediment treatment = 1.54 mm). As passive rejection is enhanced by tall polyps with steep surfaces ( Lasker, 1980), it is possible that this response would be beneficial to the two species tested. Any attempt to examine plastic responses of corals to chronic sediment is complicated by the reduction in light caused by sediment in the water. For instance, explanate Porites sillimaniani form branches under high light ( Muko et al., 2000).