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Introduction | Identification | Impacts | Causes | Actions | More Info
|What are some of the biological and physical impacts to coral reefs?|
In a healthy reef ecosystem, Diadema populations help keep algal growth at healthy levels so not to outcompete with corals for space on the reef. (See One Of First Attempts To Save Coral Reefs Upcoming by M. Cunningham for efforts to re-establish Diadema populations off of Florida and the Caribbean.) However, Diadema outbreaks can lead to overgrazing of reefs and can cause physical damage to corals. Feeding scars and even death may result from an over-abundance of Diadema. Too few Diadema is also a problem for reefs. Back in the 1980s a disease severely reduced the population of Diadema in the Caribbean Sea leading to increased algae growth and reduced coral cover. The die off was made worse by increased nutrients and overfishing of herbivores.
Can the absence or outbreak of Diadema impact local communities and economies?
Many cultures harvest Diadema for their roe (eggs) and therefore there is a financial value connected to Diadema. In Hong Kong, Diadema populations are large enough to support a fishery by hookah divers who collect them for their roe (Cornish 2003). However, high populations of Diadema are likely having an impact on shallow reef biota as they over graze on algae and coral. Aggregations have been observed to cause serious bio-erosion to otherwise healthy coral heads (Cornish 2003; McClanahan et al 1996). This subsequent loss of healthy coral reef habitat reduces the productivity of that reef. Local fisheries and tourism may be impacted as a result. A weakened reef structure can also make coastal communities and infrastructure vulnerable to severe storms.
|Diadema antillarum on coral rubble.
Jamaica (T. Hughes)|