Sea Star Outbreaks

Sea Star Outbreaks

There are some species that inhabit the Great Barrier Reef that can tip its balance from time to time. Among those species is the crown-of-thorns sea star (Acanthaster planci), a large sea star that can grow to diameters of more than a meter and can have up to 21 arms. The crown-of-thorns sea star is covered with long, sharp, venomous spines and can move up to 20 miles per hour.

Outbreaks of crown-of-thorns sea star can mean disaster for a reef. The starfish feed on corals and can decimate a reef in the wake of their feeding path. The first recorded outbreak of crown-of-thorns sea star on the Great Barrier Reef occurred in the 1960s. Subsequent outbreaks were recorded in 1979 and in 1994.

Although coral reefs do recover from the outbreaks, it takes decades for species diversity to return. Renewed outbreaks greatly hinder recovery if they occur at intervals that don't allow coral to regrow and communities to reestablish themselves.

Though scientists do not know for certain what causes the sea star outbreaks, they have identified a number of possibilities:

• the sea star population outbreaks are part of a natural cycle
• the decline of the starfishes' natural predators enables the outbreaks
• human disturbance such as run-off of nutrients from land have enabled the outbreaks

Sources

For a list of sources used in the creation of this visual guide, please see the Recommended Reading page.