Deep-Sea Surprise

As a shallow-water biologist, Catherine McFadden’s usual method of coral specimen collection is via SCUBA diving. She also tends to get seasick if she spends much time on a boat. So, when her colleague, deep-water biologist and Harvey Mudd postdoctoral researcher Andra Quattrini, asked McFadden to take her place aboard a two-week, deep-sea exploration cruise last summer, it was with some hesitation that McFadden agreed. Fortunately for her, she didn’t get sick, she took her first-ever dive in a submersible vessel, and she ended up being part of an exciting discovery.

McFadden on ship deck with first-dive awards.
As it was McFadden’s first dive, she was crowned Queen of the Octocorals when she arrived back on deck. With funding from the National Science Foundation, McFadden’s research group at Harvey Mudd College is developing next-generation sequencing-based target-enrichment methods to study phylogenetic relationships and skeletal evolution in anthozoan cnidarians (corals and sea anemones). McFadden is particularly interested in understanding species boundaries and the generation of biodiversity in shallow-water soft corals, and in recent years has focused on the coral reef communities of the South China Sea.

“We thought there might be some coral at the site, but I was expecting a fairly barren landscape of mud and rock with just some small, isolated coral colonies here and there,” says McFadden, the Vivian and D. Kenneth Baker Professor of Biology at Harvey Mudd College.

As the Lophelia pertusa grows and dies over many hundreds of years, new Lophelia grows atop the old skeletons, forming 80- to 100-meter high mound structures that stretch further than scientists had imagined. During nearly eight hours in the submersible, McFadden, Cordes and pilot Bruce Strickrott viewed and sampled different coral species, including Enallopsammia, Madrepora and octocorals (plexaurids, primnoids, Anthomastus). Lophelia was by far the most sampled coral.

Instead, McFadden and the expedition’s chief scientist Erik Cordes “landed on a massive coral reef formed by a mix of dead coral rubble and large, dense stands of living coral,” she says. “It’s pretty mind-blowing to know that the existence of this huge biological structure was completely unknown until now and to have been one of the first humans to visit it.”

Researchers are using the deep-sea submersible Alvin to visit previously unexplored locations, including canyons, gas seeps and coral ecosystems, in order to identify and ultimately protect sensitive habitats. Passengers can view their surroundings through any of five portholes or via a television monitor inside. The Alvin is equipped with robotic arms, which the pilot can direct to collect coral samples. A platform on the front of the Alvin holds containers designed to hold the samples. As the Alvin holds only three people at a time, scientists who remain on the ship above make a list of specimens for their diving colleagues to look for and collect when they’re underwater.