Thirty five kilometers off the Big Sur coast and 800 meters below the sea surface lies an underwater mountain range called Sur Ridge that is home to an amazing array of deep-sea animals. Staff from MBARI and the Monterey Bay National Marine Sanctuary recently worked together to create an illustrated, on-line field guide to Sur Ridge.

The Sur Ridge Field Guide includes more than 260 different species of animals, many of them beautiful and strange. On some slopes of Sur Ridge, fluorescent yellow Picasso sponges cling to the rocky seafloor, growing to half a meter tall. Elsewhere the tree-like branches of bright-pink bubblegum corals extend more than two meters above the ocean bottom.

These corals and sponges create complex, three-dimensional structures that provide habitat for many other animals such as crabs, snailfish, and blob sculpins. Farther up, in the water above the ridge, vampire squids and glistening comb jellies drift and feed in the darkness.

In some ways, Sur Ridge resembles Davidson Seamount, another underwater mountain range offshore of the Central California Coast. Over the last two decades, MBARI has conducted many research cruises and remotely-operated vehicle (ROV) dives on Davidson Seamount in collaboration with the Monterey Bay National Marine Sanctuary. These dives revealed forests of deep-sea corals that led to the seamount being added to the Sanctuary in 2008.

Eighteen kilometers (11 miles) long and four kilometers (2.5 miles) wide, Sur Ridge is considerably smaller than Davidson Seamount, and it is much closer to shore (see map). But its inhabitants are just as interesting to deep-sea biologists. Both Davidson Seamount and Sur Ridge are ecological “islands”—their rocky slopes harbor animals that cannot live on the flat, muddy seafloor nearby.

Spectacular sponge and coral gardens were first discovered on Sur Ridge in December 2013, when MBARI and sanctuary researchers conducted a six-day cruise to study deep-sea animals on the floor of Monterey Bay. Finding themselves a bit ahead of schedule, the researchers decided to head down the coast and explore Sur Ridge using remotely operated vehicle (ROV) Doc Ricketts. They were excited to discover forests of deep-sea sponges and corals growing on the dark rocks that crop out along the ridge.

Since that time, the research team, led by MBARI Senior Scientist Jim Barry, has returned to Sur Ridge five times, conducting a total of 29 ROV dives in the area. As with all MBARI ROV dives, high-definition video was recorded. After the dives, this video was painstakingly analyzed by Linda Kuhnz, a marine biologist in MBARI’s video lab. She identified every animal visible in the footage and entered this information into MBARI’s vast Video Annotation Reference System (VARS) database.

Researchers created the Sur Ridge Field Guide by “mining” the VARS database. The result is a comprehensive list of the animals seen during these dives. The field guide also includes photographs of most of these animals.

“Deep-sea organisms are not well known and few field guides are available to provide a clue to their identities and the interrelationships,” said Barry. “The Sur Ridge Field Guide provides a quick source of information for scientists and others interested in the invertebrates and fishes inhabiting this curious habitat, far below the sea surface.”

You can read an article about the new field guide on the Monterey Bay National Marine Sanctuary web site or view the entire field guide here.

Article by Kim Fulton-Bennett

Watch a short video of sponges and corals on Sur Ridge:

For additional information or images relating to this article, please contact pressroom@mbari.org.