Report from the Pacific Seas

May 13, 2022

Researchers conduct seafloor mapping and coral reef assessment in the Mariana Archipelago.

Feature Story |

Pacific Islands

A scientist conducts a reef fish survey at Aguijan Island. Credit: NOAA Fisheries/Mia Lamirand.

In March, the Rainier Integrates Charting, Hydrography, and Reef Demographics mission aboard the NOAA Ship Rainier kicked off its first leg. In this mission, scientists with different backgrounds share the goals of measuring water depths, mapping the seafloor, and gathering information on coral reef habitats. The data from this mission will support efforts in the region including the National Coral Reef Monitoring Program’s long-term coral reef monitoring and nautical charts.

The coral reef scientists recently completed their first 24-day survey. One team conducted 108 surveys around the islands of Guam, Saipan, Tinian, Aguijan, and Rota. They assessed their reef fish populations by counting the number of each species of fish and estimating their sizes. The team counted all kinds of fish, from stingrays to anemonefish.

anemone fish on a coral reef — A curious anemonefish looks at a diver during a fish survey at Tinian Island. Credit: NOAA Fisheries/Matt Chauvin.

Another coral reef team was busy measuring ocean conditions with an array of instruments. They collected water samples at 94 sites, and retrieved and deployed more than 130 instruments! These instruments measured water temperature, depth, currents, pH, dissolved oxygen, and light.

dive team on a small boat — The ocean and climate change team prepare a suite of instruments to carefully lower to the seafloor to record environmental information. Credit: NOAA Fisheries.

The scientists also photographed the seafloor to create three-dimensional models of the reefs, which will show what is growing on them. At sites that are re-visited over time, they will see how much coral has grown or if coral colonies have died. Read more about these models.

divers conducting a survey — Divers swim in concentric circles collecting images of the reef that they will stitch together later to form a three-dimensional model. Credit: NOAA Fisheries/K. Urquhart.

Another team mapped the shallow areas using two small boats while the Rainier collected data in the deeper areas. These mapping surveys include bathymetry (water depth) and backscatter (bottom type) data. Scientists combine them to create detailed three-dimensional maps of the seafloor and its different habitats. These maps will update nautical charts and support marine resource management in the region. The Rainier charted areas that have not been surveyed in more than 80 years!

Bathymetry for Guam and Rota — Areas the Rainier has surveyed for both mapping and corals as of May 1, 2022. Blue dots represent completed coral survey sites around the islands. Shaded colors around the islands indicate the range of water depth from the shallow (red) to the deep (purple). Credit: NOAA Office of Coastal Survey.

This is just the beginning of the Rainier’s mission, which will run through August. For now, these scientists have traveled back to Honolulu and a new group of coral researchers have joined the ship. Be sure to follow the progress on our coral and mapping story maps and the Rainier’s Facebook page!