Scientists find remote coral atolls with intact marine ecosystems in the Pacific

Scientists conducted a research expedition in 2023 to survey the Bikar and Bokak coral atolls in the Marshall Islands, a country in the Pacific Ocean.

These atolls were declared the first national marine sanctuary in the Marshall Islands last year. The researchers aimed to provide a comprehensive assessment of these remote ecosystems to understand how tropical marine systems function in the Anthropocene, a current geological age defined by significant human impact.

The study revealed that these atolls represent some of the most intact ecosystems in the region due to their extreme isolation. Bikar sits more than 100 kilometers from the nearest inhabited atoll, while Bokak is nearly 400 kilometers away from human settlements. The expedition observed 266 reef fish taxa and 17 seabird species. Researchers also found high biomass of large predators, with sharks making up 26.8 percent of the fore-reef biomass at Bikar and 33.9 percent at Bokak.

Using submersibles and deep-sea cameras, the team documented 138 fish taxa at depths up to 275 meters and another 79 groups at even greater depths. The findings showed that 14 of these groups were previously unreported records for the Marshall Islands. While the atolls are relatively untouched by local human pressure, the researchers noted that they still face global threats like warming waters and ocean acidification. They also found populations of introduced Polynesian rats on both atolls.