Coral Surveys at Kingman Reef

by the Paleo-Benthic Team

Dead Acropora branches and plates were abundant on Kingman, such as at this patch reef, but there was very little live Acropora. Photograph by Marie Kospartov.

Kingman Reef was amazing. The sharks, manta rays, dolphins and large fish thrilled us. Fields of colossal Porites corals, some more than 3 m in diameter, covered the back-reef and patch reefs, while the spaces in between were blanketed by teams of technicolor Tridacna clams. We [the Paleo Benthics] collected core samples from ten Porites colonies scattered around Kingman. In general, the colonies appeared quite healthy, with only a very few patches of partial mortality. Some of them had quite abundant bite-marks from fish and other predators, and several had scars where a crown-of-thorns starfish had munched. The sharks seemed attracted by the sound of the drill but mostly didn’t get uncomfortably close—except one day when a fish escaped from the Fish Team and swam directly over us, accompanied by a squadron of sharks hoping for an easy meal.

Jessica Carilli keeps an eye on a gray reef shark in the distance while coring a massive Porites colony. Photograph by Marie Kospartov.

One thing we hadn’t expected was the low abundance of live Acropora in the back and patch reefs. These corals can form extensive branching thickets, tables, and small pillow-shaped branching colonies. They are one of the most spectacular sights on a reef. However, at Kingman we only saw live Acropora on the fore reef and on very shallow parts of the back reef. At some sites there was good cover, but at other fore reef sites we saw large dead plates, still attached in their original position. Dead Acropora colonies were particularly striking at one of the patch reefs where we worked. Here Marie’s surveys found an abundance of dead Acropora branches and plates, while the largest live Acropora she observed was only about 4 cm in diameter. In fact, there were quite a few of these tiny baby Acropora “recruits.” We hypothesize that some event—perhaps the mass coral bleaching event in 1998 or one of the recent outbreaks of the coral-eating crown-of-thorns starfish —killed off the Acropora. Now the population is showing the first signs of recovery supplied probably with coral larvae from the fore reef where live Acropora still exist.

Kingman Reef thus offered us the unusual opportunity to document recovery from bleaching on a reef that is otherwise unimpacted by humans. We took advantage of this by conducting additional surveys on this patch reef. Here we quantified the genus, number, and size of the recruits, and also collected samples of dead Acropora plates and branches to date using radiometric techniques (which will tell us when they were last alive). If most of those recruits that we saw do survive to adulthood, this patch reef should look markedly different in 5 to 10 years time, with massive Porites again sharing the reef withplating and branchingAcropora. It is our hope that remote reefs like Kingman that have been spared local human disturbance may be resilient enough to weather the bleaching and other stresses that lie ahead.