Seamounts are large underwater mountains that rise hundreds, or even thousands, of feet from the seafloor. Often formed by volcanic activity, they are found in every ocean basin on the planet and provide critical habitat for a variety of ocean life, including corals, mollusks, crustaceans, fish, and marine mammals. These geologic formations attract many migratory and highly mobile species, such as tuna, sea turtles, sharks, and whales. Yet, despite their abundance, less than 0.1% of the world’s seamounts have been explored.
Seamounts teem with marine life
Seamounts have steep flanks that steer ocean currents in complex patterns. This results in an upwelling of nutrients, such as nitrates and phosphates, that help stimulate phytoplankton growth and provide food for myriad species. In addition, these currents remove waste and reduce sediment buildup on seamounts, fostering an ideal habitat for cold-water coral and sponge communities, which in turn provide habitats for a wide variety of life. It is no wonder that seamounts hold cultural significance for many island communities and artisanal fishermen who rely on these productive fishing grounds.
Experts speculate that seamounts, because of their isolation, have high levels of biological endemism: species that are found nowhere else. Researchers estimate that seamounts host 15% to 35% of all endemic species and are particularly important sites for deep-sea fauna. Experts also theorize that the large numbers of highly mobile species drawn to seamounts visit them to feed, breed, nurse their young, rest, or seek refuge from predators. Researchers also believe that whale and shark species use seamounts’ unique geomagnetic signatures—created as volcanic rock solidifies, locking in the magnetic field of that time—to help them navigate the open ocean.
Seamounts are threatened by human activity
Seamounts face increasing threats from large-scale fishing, deep-sea mining, and climate change. Highly mobile species such as tuna form larger schools around seamount peaks than in the open ocean, attracting industrial fishing vessels. In addition, seamounts are particularly vulnerable to bottom trawling, a fishing method that indiscriminately scrapes the seafloor and destroys much of the life there, including unique ecosystems.
Some seamounts are also coated in valuable minerals—such as nickel, copper, and cobalt—that have attracted industrial interest. Mining on or around seamounts could destroy them, killing marine life in the immediate vicinity and removing the metal-rich seafloor that many marine flora and fauna need to survive. In addition, plumes of mining-related sediment can smother life beyond mining zones.
Studies show that many of the species found on seamounts are extremely sensitive to changes in ocean chemistry and, perhaps, temperature. For example, increased carbon dioxide levels caused by climate change result in ocean acidification, which decreases the growth and structural integrity of corals.
According to the International Union for Conservation of Nature, many seamount species grow slowly and take years to reach reproductive age, making them particularly vulnerable to habitat degradation and overexploitation. For example, coral and sponge species found on seamounts often live to be thousands of years old and are among the oldest known creatures on the planet. These ecosystems will take decades to thousands of years or more to recover from damage or destruction, depending on the severity of the impact.
Seamounts need increased protections
As researchers uncover more compelling information about the biological significance of seamounts, policymakers are increasingly committed to conserving these unique geological formations. In 2016, President Barack Obama expanded the Papahānaumokuākea Marine National Monument northwest of the Hawaiian Islands, creating what was at the time the largest protected area in the world. This decision honored the area’s spiritual and ancestral significance for Native Hawaiians and helped safeguard the corals, sponges, and other marine life that live on seamounts in these waters. Similarly, Mexican President Enrique Peña Nieto designated the Revillagigedo Archipelago National Park in 2017, fully protecting the volcanic chain of islands and seamounts from fishing and other extractive activities.
Seamounts play a vital—although only partially understood—role in marine ecosystems across the globe. Yet the vast majority of these biodiversity hot spots are still unexplored and unprotected. With threats mounting to these remarkable habitats, more governments should move to safeguard seamounts. Marine protected areas and other effective conservation measures could help insulate them from further destruction, safeguard the livelihoods and culture of coastal communities that depend on them, and preserve their benefits to biodiversity and ocean health for generations to come.
Ashleigh Cirilla is a senior manager and Rebecca Jablonski-Diehl is an associate manager with the Pew Bertarelli Ocean Legacy Project. Diva Amon is a deep-sea biologist, founder of SpeSeas, and a Pew Bertarelli ocean ambassador.