HONOLULU, September 13 — The economic case for mapping the deep Pacific rests on a simple constraint: ship time and remotely operated vehicle dives are expensive, and the seafloor is vast. Scientists at NOAA Fisheries’ Pacific Islands Fisheries Science Center are using species distribution models to predict where deep-sea corals are most likely to occur across the Pacific Islands, filling gaps left by the limited reach of ship and ROV surveys.
The work sits inside the Pacific Islands Deep-Sea Ecosystems of Sponges and Corals: Exploration, Investigation and Technology, or DESCENT, Initiative. One of DESCENT’s core goals is to develop broad-scale distribution and habitat-suitability models that improve understanding of deep-sea coral and sponge communities and support ecosystem-based management.
Why the models matter
Deep-sea corals occur hundreds to thousands of meters below the surface, often on steep slopes, seamounts, ridges, and other complex seafloor features. These habitats provide three-dimensional structure for fishes and invertebrates. But because ROV surveys can cover only a small fraction of this vast region, understanding of where deep-sea corals are found based on imaging alone remains limited.
That is where the modeling comes in. To build and apply the models, researchers combine observations collected over decades from multiple sources, including NOAA’s national deep-sea coral and sponge records, the Global Biodiversity Information Facility, the Ocean Biodiversity Information System, and the University of Hawaiʻi’s Deep-sea Animal Research Center.
For roughly 30 deep-sea coral species, the team matches known occurrence locations with environmental information describing conditions such as depth, temperature, salinity, dissolved oxygen, nutrients, chlorophyll, and ocean currents. The species distribution model looks for patterns in this dataset to estimate where each species is most likely to live and overlays those patterns.
From species to hotspots
The models estimate where each coral species is likely to occur by relating observed locations to the environmental conditions the coral was experiencing at the time it was observed. These species-level predictions can highlight broader patterns in expected coral richness and identify potential biodiversity hotspots. The resulting maps are predictions rather than direct inventories of the seafloor and are intended to complement field observations.
The predictions provide researchers with limited ROV time on the seafloor information needed to target areas to further investigate. Preliminary results suggest clear spatial patterns for the Main Hawaiian Islands.
Higher modeled coral richness follows many slopes, banks, and deep features surrounding the islands, while smaller areas emerge as the highest-ranking hotspots. On the map, highlighted cells represent areas with the highest modeled hotspot values, with the most concentrated areas identified as “core” hotspots. These areas provide precise target zones for upcoming seafloor expeditions.
The approach is already tied to fieldwork. A squat lobster was observed living in the branches of a coral during Dive 01 of the 2026 American Samoa ROV + Mapping Exploration expedition, with the image courtesy of NOAA Ocean Exploration, 2026 American Samoa ROV + Mapping Exploration.
What to watch next is whether the core hotspots identified around the Main Hawaiian Islands translate into confirmed coral communities when expeditions reach them. Each confirmed match would sharpen the models and give managers a cheaper way to decide where to send the next dive.
