, 1965, Amesbury, 1981, Rogers, 1990, Gilmour, 1999 and Bray and Clark, 2004). It
may also, however, cause increased rates of asexual reproduction in free-living corals that show partial mortality (Gilmour, 2002 and Gilmour, 2004). Furthermore, cover by sediment interferes with the coral’s feeding apparatus, by causing polyps to retract and tentacular action to cease. Sufficient sediment Apoptosis inhibitor overburden may make it completely impossible for corals to expand their polyps and thus can inhibit the coral compensating for its losses in autotrophic food production by heterotrophic activity. While some corals are able to ingest sediment particles in turbid conditions and derive some nutritional value from them (Rosenfeld et al., 1999 and Anthony et al., 2007) or even build up higher lipid energy reserves (Anthony, 2006), most corals cease activity when confronted with heavy sediment loads. Corals can withstand a certain amount of settling sediment, as this occurs naturally (Rogers, 1977, Rogers, 1990 and Perry and Smithers, 2010). Many species have the ability to remove sediment from their tissues, either passively (through
their growth form) or actively selleck chemicals (by polyp inflation or mucus production, for example). Sediment rejection is a function of morphology, orientation, growth habit and behaviour of the coral and the amount and type of sediment (Bak and Elgershuizen, 1976). Corals growing in areas where they typically experience strong currents or relatively high wave energy generally have no need for effective (active) sediment rejection mechanisms, as the turbulence of the water assists in the passive cleaning of any sediment that may have accumulated on the coral tissue (Riegl et al., 1996 and Hubmann et al., 2002; Sorauf and Harries, 2010). Many branching corals appear very effective in passive rejection of sediment because of their colony morphology, but they may suffer from reduced light levels. Massive and plating coral colonies,
on the other hand, though usually more tolerant of turbid conditions, are more likely to retain sediment because of their shape and a lack of sediment rejection capabilities and thus tend to have a relatively low tolerance nearly to sedimentation (Brown and Howard, 1985). Various species of free-living mushroom corals that live on reef flats and slopes can occur on a range of substrata, whereas those that live deeper on the sandy reef bases usually live on sediment (Hoeksema and Moka, 1989, Hoeksema, 1990 and Hoeksema, 1991b). As juveniles, mushroom corals live attached and only after a detachment process do they become free-living and mobile (Hoeksema, 1989, Hoeksema, 2004 and Hoeksema and Yeemin, 2011). Some free-living mushroom coral species show a large detachment scar and their juveniles remain relatively long in the attached anthocaulus phase.