One of the greatest biological threats to tropical coral reefs can be a population outbreak of crown-of-thorns (COT) sea stars (Acanthaster planci). Outbreaks can consume live corals over large areas, a change that can promote algal growth, alter reef fish populations, and reduce the aesthetic value of coral reefs, which in turn negatively affects tourism. Despite more than 30 years of research, the triggers and spread of COT outbreaks are not fully understood. Human impacts such as urbanization, runoff, and fishing have been correlated with outbreaks, but some outbreaks continue to occur in the absence of known anthropogenic triggers. Waves of a spreading outbreak that moves southerly along the Great Barrier Reef are termed secondary outbreaks because they are thought to be seeded from dispersing larvae of a primary outbreak upstream.
This secondary outbreak hypothesis has been widely accepted as the mechanism by which COT outbreaks spread across broad regions of the Pacific Ocean and impact remote locations such as Hawai'i, Guam, or French Polynesia - until now. A team of scientists from the Hawai'i Institute of Marine Biology and the Joint Institute for Marine and Atmospheric Research at the University of Hawai'i and Rutgers University have recently used genetic techniques to evaluate the spatial scale at which COT outbreaks can occur via larval dispersal across the central Pacific Ocean. The results of this work have demonstrated that unlike on the Great Barrier Reef, COT larvae are not moving en masse among central Pacific archipelagos. In fact, contrary to expectations under the secondary outbreak hypothesis, all COT outbreaks in the study came from local populations. On a finer scale, genetic differences were detected among reefs around islands and even between lagoon and forereef habitats of the same island, indicating that the larvae of this species are not routinely reaching their full dispersal potential, and are certainly not fueling
|Contact: Carlie Wiener|
University of Hawaii ‑ SOEST