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Modeling Mountains: How Species Modeling Could Save the High Seas

Far off the South American coast lie submerged mountain ridges that stretch nearly 2,000 miles along the seafloor. While these seamounts are deep, remote, and mysterious, habitat modeling offers insight into what animals live in these biodiversity hotspots. Our Marine Biogeographer Dr. Sam Georgian discusses a new publication detailing how cutting-edge species distribution models are used to support conservation efforts on the last exploration frontier of our planet – the high seas.

For a marine biologist, I spend surprisingly little time on the ocean. Most of my job involves analyzing data, creating maps, and writing code for ecological models – all in an effort to help us better understand the areas that we need to protect. My desk in Seattle, WA might not look like the pilot seat of a submarine, but every day I transform into a deep-sea explorer, creating habitat maps that reveal important information about dazzling seascapes that few humans have seen in person. Although I’ve been lucky enough to go out on ships and submersibles to explore ocean ecosystems, I’ve discovered that species distribution modeling might be the key to building a strong scientific case for conserving fragile ecosystems that exist beyond the reach of costly research expeditions. Currently, I’m working with the Coral Reefs of the High Seas Coalition to put these cutting-edge modeling techniques to the test using data from the coast of South America. What our models have revealed will help guide a suite of ongoing science and conservation efforts throughout the region.

The Salas y Gómez and Nazca ridges are adjacent seamount chains that lie offshore the coasts and Peru. The ridges contain over 110 seamounts, the vast majority occurring in waters that are outside of any national jurisdiction, a remote part of the ocean commonly known as the high seas. These seamount chains support an exceptionally rich biodiversity, with the highest rate of marine species found nowhere else in the world (>40%). The highly productive waters above the ridges contain important feeding grounds and migratory pathways for numerous ecologically important species including sea turtles, seabirds, and whales. The seamounts themselves house extensive communities, including a variety of deep-sea corals and sponges, which provide the foundation for some of the most diverse ecosystems in the deep sea with thousands of associated species. Corals and sponges also contribute significantly to carbon and nutrient recycling in the deep sea, and are used by scientists for important biomedical discoveries and as paleoclimate archives. Unfortunately, their slow-growth rates, low reproductive outputs, and sensitivity to disturbance make these communities highly vulnerable.

Human activity could swiftly and significantly damage the Salas y Gómez seamount habitats, which have until now remained relatively—and tenuously—pristine. Unfortunately, achieving effective conservation on the high seas is difficult due to the lack of a legal framework to create high seas marine protected areas, and the lack of general awareness that unique and fragile ecosystems exist in these remote areas. Accordingly, only 1.2% of the high seas is protected, leaving the vast majority of high seas susceptible to damage from destructive fishing practices, pollution, oil and natural gas extraction, deep-sea mining, and climate change.

The sheer size of the high seas – spanning more than 61% of the ocean – is a significant obstacle to science and conservation. Due to the large costs of surveying remote areas, the vast majority of the high seas remains completely unexplored, presenting a major challenge to identify priority areas for conservation. Species distribution models are powerful tools to understand where fragile and unique ecosystems are likely to occur, even in places that have not yet been explored in detail. The models link broad environmental data with known locations of species of interest to predict the likely distribution of these species. Since these models predict species distributions even in areas that have not yet been explored in detail, they are particularly useful to guide science and management efforts in remote places like the high seas. Marine Conservation Institute has a long history of using species distribution models to aid conservation efforts in many locations around the globe, including  the South Pacific, British Columbia, and the Gulf of Mexico.

Map of the Salas y Gómez and Nazca ridges, two seamount chains that stretch across nearly 2,000 miles off the coast of South America.

In a recent publication in PeerJ, we produced species distribution models for stony corals and two groups of sponges (demosponges and glass sponges) across the Salas y Gómez and Nazca ridges. The research was conducted in collaboration with the Coral Reefs of the High Seas Coalition, a global alliance of partners that aims to protect coral reefs throughout the high seas. Previous work by the coalition has already shown that the Salas y Gómez and Nazca ridges contain discrete patches where diverse, rare, and unique assemblages of marine life occur, thereby underscoring the importance for protecting this region. The results of our new modelling study highlight that deep-water corals and sponges, species that are considered top conservation priorities globally, are widespread throughout the region. Importantly, the models allowed us to predict where these communities occur even on seafloor features that have not yet been explored. Coral and sponge ecosystems were predicted to occur on seamounts, ridges, and similar steep features, which are known to produce favorable habitats for a wide variety of marine life. These steep features accelerate currents around them, increase nutrients, and thereby provide important habitat that allow corals and sponges to grow.

Deep-water corals and sponges on an unnamed seamount on Salas y Gómez ridge at a depth of 1,700 feet. Image courtesy of JAMSTEC.

Building a strong scientific case for conservation is a necessary first step for long-term protection efforts. The results of this study underscore the need to protect the diverse and fragile seamount ecosystems of the Salas y Gómez and Nazca ridges, particularly on the high seas where there are no protections. These models contribute to mounting scientific evidence that the Salas y Gómez and Nazca ridges are one of the most unique diversity hotspots on Earth. We must act now to protect these unique and fragile resources before it is too late. 

Desmophyllum sp.- NOAA

The deep-water, reef-building coral (Madrepora sp.), which is known to build highly biodiverse reefs on the Salas y Gómez and Nazca ridges. Photo courtesy of NOAA.