Back to the Marianas: Monitoring Coral Reef Ecosystems in the Pacific

Join our National Coral Reef Monitoring Program scientists during their 2025 mission as they track the health, threats, and recovery of coral reef ecosystems in the Marianas.

Ecosystems |

Pacific Islands

Coral reefs are in decline, affecting coastal communities, economies, and ecosystems. To better understand and address these challenges, the National Coral Reef Monitoring Program has been collecting data since 2000 to support the protection of these invaluable ecosystems, worth more than $3.4 billion in the U.S. economy.

This year, teams of scientific divers return for the 9th time on the NOAA ship Oscar Elton Sette to continue these long-term monitoring efforts in the Marianas. These surveys are like a routine health check-up for the ocean—scientists assess fish populations, coral health, and ocean chemistry to detect changes and identify potential threats. With these insights, they can inform the most effective strategies to support reef conservation and resilience.

The Pacific National Coral Reef Monitoring Program last visited Guam and the Northern Mariana Islands in 2022 to monitor fish and seafloor communities while the research ship collected bathymetric data. Findings revealed that, on average, half of the region’s coral has been lost over the past two decades. However, research also highlighted the success of Guam’s marine preserves in enhancing fish populations. Additionally, by bringing together data from 2009–2022, researchers developed a model to predict future fish distributions. This model can help local managers pinpoint key areas for conservation efforts.

NOAA Fisheries is dedicated to the stewardship of the nation’s ocean resources. Through rigorous scientific research and an ecosystem-based approach to science-informed management, we provide critical data on coral reef communities, fish populations, ocean conditions, and chemistry. This long-term, high-quality information supports scientists, resource managers, and the public, offering valuable tools like the program's data visualization tool.

Follow along to see the science behind our 2025 mission!

USFWS Special Use Permit (Ritidian Point) #12518-25006
NPS Scientific Research and Collecting Permit #WAPA-2025-SCI-0003
CNMI DLNR DFW Scientific Research License # SRC25-10-RE
Guam DAWR Research Permit #SCR-MPA-25-008

This year, we’re returning to the Mariana Archipelago to continue stewardship of U.S. coral reef ecosystems. Here, the N...

Cast off! After preparations and loading, the NOAA Ship R/V Oscar Elton Sette departed from Pearl Harbor, Honolulu on Ma...

These photos, taken before (left) and during (right) a bleaching event in 2016 at Jarvis Island, demonstrate the importa...

Despite swells and windy conditions, we began surveys at Wake Atoll on April 3rd, thanks to the skilled ship crew. In th...

Parrotfish play a critical role in maintaining healthy coral reef ecosystems. By comparing their populations across diff...

In addition to our typical fish, benthic, and oceanographic surveys, we also conducted towed diver surveys around the en...

During the Wake Atoll surveys we came across a lot of diversity in Acropora corals, easily visualized here. Credit: NOAA...

The logistics of dive operations off a NOAA ship are not so simple! Once a dive boat is craned over the side of the ship...

That’s a wrap for the first leg of the journey! Next stop: Guam. NCRMP surveys at Wake Atoll were a success. Ocean condi...

The NOAA Ship Oscar Elton Sette arrived in Guam on April 15! After drills and training, surveys began off Guam's western...

Prior to conducting fish surveys in the Marianas, divers must refresh their fish identification skills. Here the ringtai...

Research surveys kicked off with calm waters in Guam, allowing divers to reach shallow sites that are otherwise difficul...

While NCRMP divers rest after daytime surveys, the ocean comes alive in a different way. Far offshore—10 to 50 nautical ...

At the end of a survey day, the dive boat gets ready to come alongside the ship. The ship’s commander, driver, crane ope...

Can you find Nemo? Here, a clownfish hops from one coral to the next during a fish survey. During these surveys, divers ...

Here, a diver collects photoquadrat imagery by using a monopod stick to measure 1 meter above the sea floor. The organis...

Off Saipan, scientific divers are treated with a school of rainbow runners at the end of their survey. Rainbow runners a...

That’s a wrap on leg 2! We surveyed Guam, Saipan, and Aguijan, completing more than 100 fish and photoquadrat surveys ea...

Leg 3 of the journey has begun! During this leg we will focus on surveying the northern Mariana islands. Here a diver is...

A young damselfish protects its coral home. These fish are known to be territorial—you may see them chase other fish awa...

‘Splashing divers’ refers to the moment when divers roll off the boat to begin their descent to a survey site. Here, div...

We arrived in Pagan for four days of fish, oceanographic, and benthic surveys. Here a diver finishes up a fish and benth...

Maug is a unique structure in the Northern Marianas consisting of three islands that circle the caldera of an ancient vo...

Because underwater volcanic vents release high levels of carbon dioxide, Maug is considered a "natural lab" for scientis...

For one of our oceanographic surveys, we package several instruments into what we call a ‘diel suite’. We deploy these p...

After finishing up surveys in Maug, we made our way south and returned to Pagan. Previously, unsafe ocean conditions at ...

Corals come in all shapes and sizes! This type of coral (Porites rus) is often referred to as looking like a ‘birthday c...

We found Dory! This bright blue tang is a delight to record while divers hurriedly write down all the fish species, size...

Would you believe this is a stony coral with a skeleton just below the fleshy white surface? Bubble corals inflate their...

After Pagan, the team headed back to Saipan to finish off coral, fish, and oceanographic surveys. Here is a view from th...

Mushroom corals (left) are unique in that they are single, solitary stony corals that are not attached to any base and c...

That’s a wrap on Leg 3, with only one leg left! Here are most of the scientists from Leg 3, all ready for a break after ...

After Leg 3, in Saipan, we hosted ship tours of the Oscar Elton Sette, and also staffed a booth at the CNMI DFW Fishers ...

After a brief delay, the Oscar Elton Sette set out from Saipan for the last survey leg of the year. Here, a scientific d...

A squid duo cruises over the reef near Rota. As both predator and prey, squid play a critical role in this ecosystem and...

We’ve had a productive start to Leg 4! Favorable ocean conditions allowed us to complete 14 fish surveys, 10 benthic sur...

Continuing great weather allowed us to survey one of Guam’s more challenging coastlines, nearly wrapping up all our Guam...

Take a look at the beautiful pattern on this giant clam near Tinian! Giant clams are vital to coral reef ecosystems, act...

The weather took a turn as our team headed to Agrihan. Thunderstorms, lightning, and rough seas have made dive operation...

We got lucky with better-than-expected weather at Agrihan, giving us the rare chance to conduct surveys there for the fi...

After a day of rest and transit north to avoid stormy conditions, the Sette was rewarded with workable weather at Uracas...

A diver recovers a calcium accretion unit (CAU) that has spent the past 3 years growing on the reef. It will be analyzed...

During our fish surveys we also record habitat types. This is a classic example of a rock and boulder habitat found in l...

Despite challenging conditions from Tropical Storm Sewat, scientists successfully surveyed Guguan for the first time sin...

Last updated on 06/30/2025

Pacific Islands