A new study published in Frontiers in Marine Science offers a rare glimpse of Bikar and Bokak, two remote coral atolls in the Marshall Islands. Marine ecologist Alan Friedlander described them as some of the most intact ecosystems remaining in the region, while researchers said such ecosystems are comparatively less affected by direct local human pressures.
The findings stem from a 2023 research expedition that surveyed the atolls, which last year were declared the Marshall Islands’ first national marine sanctuary. Marine ecologist Alan Friedlander of the University of Hawai'i said the atolls “are not just treasures for the Marshall Islands but for the entire planet, a gift from the community of Utirik Atoll, which has traditionally and vigilantly safeguarded these fragile ecosystems for decades.”
Bikar is situated over 100 kilometres from the nearest inhabited atoll, while Bokak lies almost 400 kilometres from people. The researchers wrote that remote oceanic atolls remain comparatively less affected by direct local human pressures.
The expedition observed 266 reef fish taxa from 38 families, with greater fish biomass at Bokak. Sharks accounted for the largest individual component of fore-reef biomass, 26.8 percent at Bikar and 33.9 percent at Bokak. Using submersibles, scientists documented 138 fish taxa at depths up to 275 metres, noting that 14 of the groups appeared to represent previously unreported records for the Marshall Islands. Deep-sea cameras observed an additional 79 groups of fishes at even lower depths. The team also recorded 17 seabird species, and 71 turtle crawls and 132 turtle nest pits, concentrated largely at Bikar.
“These atolls have extensive seabird colonies, mature native vegetation, active turtle nesting, high reef-fish biomass and large predators, coral-dominated reefs at Bokak, structurally complex mesophotic habitats, and surprisingly diverse and poorly known deep-sea communities,” Friedlander said. “They are among the best ecological reference systems we have to better understand what we have lost elsewhere.”
Even these remote havens show signs of ecological interference. At the time of the surveys, both atolls contained populations of introduced Polynesian rats. The atolls are also not shielded from global trends of warming waters, coral bleaching and ocean acidification.
“We use ‘relatively intact’ as a comparative description rather than as an assumption that remote reefs represent pristine or historically undisturbed states,” the researchers wrote. “Remoteness can reduce some forms of direct local human pressure, but it does not eliminate historical, introduced, or global anthropogenic influences.”
The contrast with another atoll was stark: days after surveying Bokak, the expedition moved to Bikini Atoll, the site of US nuclear tests in the mid-20th century. An expedition member wrote in a field diary that “the bombing vaporized three islands and left behind radioactive contamination that, to this day, leaves the atoll uninhabitable” and that “the first dives found some fish and a few spots with live coral, but also a lot of pulverized, dead reef with not much living on it.”
The study appears in Frontiers in Marine Science.
Analysis
Why This Matters
- The atolls serve as a baseline for what healthy coral reef ecosystems looked like before widespread human impact, offering reference points for conservation and restoration efforts worldwide.
- Their declaration as the Marshall Islands' first national marine sanctuary underlines the growing importance of large, remote protected areas in global ocean conservation strategies.
- The findings also highlight that even the most remote ecosystems are vulnerable to global climate pressures and introduced species, complicating their long-term preservation.
Background
The atolls of Bikar and Bokak lie in the central Pacific, hundreds of kilometres from populated islands, and have been traditionally safeguarded by the community of Utirik Atoll for decades. In 2024 they became the Marshall Islands' first national marine sanctuary. The 2023 expedition, the most comprehensive assessment of these ecosystems, integrated surveys from land to the deep sea. Many remote atolls have suffered degradation from overfishing, pollution, nuclear testing or climate change; Bikini Atoll, surveyed immediately afterwards, remains uninhabitable from radioactive contamination left by US nuclear tests.
Key Perspectives
Marine ecologist Alan Friedlander (University of Hawaii): Said Bikar and Bokak "are not just treasures for the Marshall Islands but for the entire planet" and that they are "among the best ecological reference systems we have to better understand what we have lost elsewhere."
The study authors: Cautioned that "relatively intact" is a comparative description and that remoteness "does not eliminate historical, introduced, or global anthropogenic influences."
What to Watch
- Whether management plans for the new marine sanctuary address the introduced Polynesian rat populations and whether eradication efforts are considered.
- Continued monitoring of coral health at both atolls in coming years as ocean temperatures rise and bleaching events become more frequent.
- Potential expansion of protection to other remote central Pacific atolls, and whether the sanctuary becomes a model for other nations.
Checked
12 claims in this story checked against 1 source: 10 supported.
Show each claim
- Partly supportedThe field-diary quote says, “the bombing vaporized three islands and left behind radioactive contamination that, to this day, leaves the atoll uninhabitable.”ScienceAlert: “"In those years, the bombing vaporized three islands and left behind radioactive contamination that, to this day, leaves the atoll uninhabitable," an expedition member wrote in a field diary.”
- SupportedA marine ecologist called Bikar and Bokak some of the most intact ecosystems remaining in the region.ScienceAlert: “There is good reason to enforce protection of these special places, as they represent some of the most intact ecosystems remaining in the region, according to marine ecologist Alan Friedlander from the University of Hawai'i.”
- SupportedThe story quotes Friedlander saying Bikar and Bokak are treasures for the Marshall Islands and the planet, gifted by the Utirik Atoll community, which safeguarded them for decades.ScienceAlert: “"Bikar and Bokak are not just treasures for the Marshall Islands but for the entire planet, a gift from the community of Utirik Atoll, which has traditionally and vigilantly safeguarded these fragile ecosystems for decades," Friedlander says.”
- SupportedFriedlander called the atolls ecological reference systems that can help explain what has been lost elsewhere.ScienceAlert: “"They are among the best ecological reference systems we have to better understand what we have lost elsewhere and to provide fundamental insights needed for effective conservation and restoration efforts."”
- SupportedThe researchers said they use “relatively intact” comparatively, rather than to imply pristine or historically undisturbed reefs.ScienceAlert: “"We use 'relatively intact' as a comparative description rather than as an assumption that remote reefs represent pristine or historically undisturbed states," the researchers write.”
- SupportedThe researchers said remoteness can reduce some direct local human pressures but does not eliminate historical, introduced or global anthropogenic influences.ScienceAlert: “"Remoteness can reduce some forms of direct local human pressure, but it does not eliminate historical, introduced, or global anthropogenic influences, and ecological condition should therefore be evaluated from observed ecosystem attributes rather than remoteness alone."”
- SupportedThe field-diary quote says the first dives found some fish and a few live-coral spots, as well as pulverized dead reef with little living on it.ScienceAlert: “"The first dives found some fish and a few spots with live coral, but also a lot of pulverized, dead reef with not much living on it."”
- SupportedSurveys of Bikar and Bokak revealed high fish biomass, large predators and extensive seabird colonies.ScienceAlert: “"These atolls have extensive seabird colonies, mature native vegetation, active turtle nesting, high reef-fish biomass and large predators, coral-dominated reefs at Bokak, structurally complex mesophotic habitats, and surprisingly diverse and poorly known deep-sea communities," Friedlander says.”
- Partly supportedBoth atolls have introduced rats.ScienceAlert: “At the time of the 2023 surveys, both Bikar and Bokak contained populations of introduced Polynesian rats ( Rattus exulans )”
- SupportedBikar and Bokak were declared the Marshall Islands’ first national marine sanctuary last year.ScienceAlert: “In a new study in Frontiers in Marine Science, scientists surveyed the Bikar and Bokak coral atolls, which last year were declared the first national marine sanctuary in the Marshall Islands.”
- SupportedThe expedition observed 266 reef-fish taxa from 38 families, with greater fish biomass at Bokak.ScienceAlert: “The field expeditions – which helped inform and secure Bikar and Bokak's protected status – observed 266 reef fish taxa from 38 families, with greater biomass of fish seen at Bokak.”
- SupportedSharks were the largest individual component of fore-reef biomass, making up 26.8 percent at Bikar and 33.9 percent at Bokak.ScienceAlert: “Sharks were a standout, representing the biggest individual component of fore-reef biomass, accounting for 26.8 percent at Bikar and 33.9 percent at Bokak.”
