Scripps expedition provides new baseline for coral reef conservation

From sharks to microbes, scientists capture key data at the central Pacific's Line Islands archipelago

Line Islands coral reef habitats (left column) and bottoms (right column) are depicted across four atolls exhibiting declining states of health, from a reef dominated by top predators and coral... Click here for more information.

An ambitious expedition led by scientists at Scripps Institution of Oceanography at UC San Diego to a chain of little-known islands in the central Pacific Ocean has yielded an unprecedented wealth of information about coral reefs and threats from human activities.

The exploration of four atolls in the Line Islands, part of a chain approximately a thousand miles south of Hawaii, has produced the first study of coral reefs comprehensively spanning organisms from microbes to sharks. This in-depth description was replicated across a gradient of human impacts, from uninhabited Kingman Reef to Kiritimati, also called Christmas Island, with a population of 5,000 people.

The results are published in two papers in the Public Library of Science (PLoS) ONE (Feb. 27) journal and a companion essay in PLoS Biology (Feb. 26).

At Kingman, the researchers described one of the planet’s most pristine coral reefs, a resource they say provides a much-needed baseline for the conservation of coral reefs. In one paper, the scientists describe Kingman’s atypical food web, where predators such as sharks accounted for 85 percent of the total fish biomass (the weight of all fish together). This inverted pyramid, they say, runs contrary to the bottom-heavy pyramids seen in other parts of the world where top predators have been fished out. Kingman also exhibited healthy coral populations and was nearly absent of seaweed and had low microbe concentrations, unlike evidence found elsewhere on disturbed reefs.

A comparison of Kingman with other reefs in the Line Islands revealed increasing levels of human impacts, including declining coral health, fewer and smaller fish and an increase in microbes.