Researchers
tackle the coral-killing starfish
February 2013. Crown-of-thorns Acanthaster
planci is the principle natural enemy of reef-building corals.
Outbreaks of this coral-feeding starfish occur periodically, due to reasons
that remain unclear. It decimates entire reefs in the space of just a few
years, as has been the case in French Polynesia since 2004. A new study
conducted by IRD researchers and their partners describes this population
explosion around Moorea, the "sister island of Tahiti". The rate of
living coral cover in ocean depths and lagoons alike dropped from 50% (healthy
reef) to under 5% in 2009. The ecosystem will need at least a decade to be
restored to its original state.
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| Photo: Kurt Domingo |
The
starfish has spread from island to island
The archipelago has been suffering from a new population explosion of the predatory starfish since 2004. It is one of the most intense and devastating outbreaks ever recorded. The outbreak of Acanthaster began in a very specific location in the Austral and Leeward Islands, then in 2006, the starfish colony spread to Tahiti and Moorea. Thanks to a dozen stations around the island of Moorea, scientists were able to make spatio-temporal observations of the dynamics of the infestation of coral populations. Thus, in a new study published in PLoS One, they described the spread of the coral reef invasion.
The archipelago has been suffering from a new population explosion of the predatory starfish since 2004. It is one of the most intense and devastating outbreaks ever recorded. The outbreak of Acanthaster began in a very specific location in the Austral and Leeward Islands, then in 2006, the starfish colony spread to Tahiti and Moorea. Thanks to a dozen stations around the island of Moorea, scientists were able to make spatio-temporal observations of the dynamics of the infestation of coral populations. Thus, in a new study published in PLoS One, they described the spread of the coral reef invasion.
Ocean
depths and lagoons alike
The starfish first settled in the deeper areas along the outer slopes of the reef, around 20 to 30 metres below the ocean surface. It then rose to a depth of approximately 6 metres, and even colonised certain parts of the lagoon. The damage was gradually observed: from 47% of living coral cover at one of the stations in 2006, for example, this rate dropped to 21% in 2007, 6% in 2008 and 2% in 2009: a disastrous state of affairs that disrupts the structure and functioning of all reef communities (including other coral-feeding species, such as butterflyfish, etc.).
The starfish first settled in the deeper areas along the outer slopes of the reef, around 20 to 30 metres below the ocean surface. It then rose to a depth of approximately 6 metres, and even colonised certain parts of the lagoon. The damage was gradually observed: from 47% of living coral cover at one of the stations in 2006, for example, this rate dropped to 21% in 2007, 6% in 2008 and 2% in 2009: a disastrous state of affairs that disrupts the structure and functioning of all reef communities (including other coral-feeding species, such as butterflyfish, etc.).
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