Getting to the bottom of the oceans’ tallest peaks

By Jordan Macke

Coldwater corals at Rodriguez Seamount. Photo: MBARI.

Our oceans are home to a number of globally rare habitats that marine animals rely on. These areas are often characterized by the presence of endemic species and are usually teeming with life. Unfortunately, the qualities that make these places unique also make them incredibly vulnerable. Seamounts—undersea mountains—have been at the center of recent conservation discussions and U.S. legislative action on protecting important ocean habitats and are a great example of vital, yet vulnerable habitats that needs protection.

Seamounts exist across every ocean basin and create some of the largest peaks on the planet, yet as of 2009[1] only approximately 1,000 seamounts have been examined well enough to be given a name and displayed on charts (satellite-collected data indicate there are likely between 15,ooo and 100,000 seamounts worldwide) [1]. Though relatively few seamounts have been explored, what we know of the ones that have been studied reveals a magnitude of reasons to protect them.

An Island Oasis in a Great Expanse

A) Diagram of a seamount community
B) Photo of a ‘‘City of Brittlestars.” Photo: CenSeam-NIWA.

The ocean floor covers ~70% of the Earth’s surface and consists primarily of abyssal plains coated in fine mud [2].  This lack of hard substrate is a large obstacle for species such as sea anemones and corals that need hard substrate to attach onto. Because seamounts are often exposed to high currents, sediments are swept from the flanks of seamounts providing a hard surface for these “rooting” animals in an expanse of open ocean. For seamounts that reach up from the depths to near the surface, these rocky areas receive sunlight allowing photosynthetic organisms (think: algae) to thrive at great depths. In fact, the record set for observation of benthic algae is 268 meters found near a seamount [2]!

A Place to Grab a Quick Bite

A benthic octopus at Gorda Ridge. Photo: MBARI.

Seamounts support incredibly diverse ecosystems. Partly, this is because they create locally accelerated currents that generate exceptionally high productivity and remove sediments from hard surfaces. In short, if you’re a sea animal that needs lunch, seamounts are where you’ll want to be. Seamounts intercept ocean currents, which sets up unique oceanographic features (stationary eddies in the waters over seamounts are called Taylor columns) that help concentrate species up and down the food chain. Plankton, an important part of the marine food web, also find themselves trapped over seamounts by these same physical forces. This gives seamount inhabitants a front-row seat to a pretty epic feast and increases overall ecological productivity by fueling the food web from the bottom up.

A One of a Kind Place to Thrive

These same Taylor columns that help increase productivity over seamounts also increase the residence time that eggs and larvae spend over seamounts. This allows them to settle safely and mature on the rocky surface below instead of being carried away by the currents. Because of Taylor columns, seamounts are home to a variety of endemic species (species that are not found anywhere else), which have settled on seamounts and are adapted only to live on, or near, these habitats. These things make seamounts very special and valuable places [2][3].

Long-Lived and Vulnerable

Okenia rosacea. Photo by Clinton Bauder

Many of the species that call seamounts home can live for a very long time. Long-lived species tend to reproduce very slowly, spend more time maturing and expend more energy rearing young. The average age of a fish living on a seamount is 12 years, while fish in other areas of the ocean have an average life span of 4-6 years. Some seamount-inhabiting fish, such as orange roughy, live to be between 100-200 years old and corals in the same habitat have been observed to be more than 4,000 years old! Unfortunately, human pressures from overharvesting, destructive trawling, deep-sea mining and oil and gas exploration mean that their lives are often cut short and the incredible genetics that allow for such resiliency are lost. Once gone, their likelihood of returning is quite poor [3].

A Reason for Hope

Several steps have been taken by legislators in different states and by former President Obama to safeguard seamount habitats. The California Seamounts and Ridges National Marine Conservation Area Designation and Management Act (H.R. 5797) was introduced during the summer of 2016 by Congressman Sam Farr and received co-sponsorship from four other Representatives. This bill would have protected seamounts, ridges and banks within the 200 nm exclusive economic zone (EEZ) of the state of California by continuing to limit detrimental human interaction, giving these pristine areas a chance at fighting climate change. There is very little area still considered ‘pristine’ on this planet, so the introduction of H.R. 5797 was an exciting first step towards the protection of California’s seamounts.

Protection of seamounts in the U.S. Atlantic Ocean has been long sought after, because these seamount chains serve as a key migration route for marine animals like whales and sea turtles. The Atlantic’s seamounts also offer a spectacular array of varied and unique sea life that need protection to survive the pressures of commercial fishing and climate change. In September 2016 President Obama permanently protected several seamounts and canyons off of New England in a marine national monument at the urging of Senator Blumenthal (D-CT), banning oil and gas exploration as well as commercial fishing.

Most recently, a national marine sanctuary proposal was drafted to protect critical habitat along Southern California’s offshore banks and seamounts. If enacted, this proposal would prohibit oil and gas extraction along with other potentially damaging industrial uses, while still coordinating necessary offshore activities. These sites are home endangered species such as white abalone, provide refuge for protected and sensitive marine mammals and could very well be home to significant archeological artifacts.

These landmark designations, proposals and legislation set the tone for a future of hope for our oceans, our planet’s life support system.  The California Seamount Coalition is working to protect the biologically sensitive and rare habitats found in our oceans.

Cover Photo by Clinton Bauder