Exploring Corals of the Aleutian Seas
Researchers tune in to deepsea corals
Part 4: Face to face with the Deep
By Sonya Senkowsky
As Jason II comes aboard, the scientists rush the most vulnerable samples, including corals, sponges and crabs, into buckets of refrigerated water, which are then hustled down the hall into a “cold room,” essentially a walk-in refrigerator. In an onboard laboratory, researchers work all night, taking pictures and preparing tissue samples for future DNA studies.
This is where we finally come face to face with the bizarre creatures we’ve been seeing from a distance. There’s a several-foot-long white spiral, the deep-sea coral Radicipes; a sponge on a three-foot-high stalk that looks like a giant mushroom; a white-legged sea spider, still alive and walking.
The corals bear little resemblance to the bleached-out pieces one collects on the beach. Fresh from the deep ocean, the pieces retrieved are covered in soft pink, red or white tissue, and it’s easy to identify a branch of coral as a colony of many individual, jellyfish-like animals, or “polyps.” These and other critters soon stink up the lab with a distinctive deep-sea stench.
Scott France, an assistant professor of biology with the University of Louisiana at Lafayette, was collecting coral tissues for genetic analysis to help identify different, and perhaps new, coral species.
Even the dives for the unrelated geology research proved fruitful, he said. “We were kind of lucky because they were sampling rocks that had a number of things attached to it, so those were bonuses. And there are some really interesting things in those bonuses. We probably have a new species of chrysogorgid, a new species of a primnoid—these are two different families of corals—and they just happened to be on a rock that was brought up, so that was fantastic!”
At the very deepest depths probed by Jason II—as deep as 2 miles below the waves—we’d seen fields of single-stalked corals poking from a muddy and otherwise largely bleak seafloor. The corals are abundant—in some cases it seems there are thousands—but their appearance was a far cry from the images of multicolored, multispecies sponge-and-coral habitats researchers brought back from shallower waters.
“The biggest surprise has been the fact that so many of the corals that we’ve seen in the deeper waters are very different from anything we’ve seen in the shallower waters,” said researcher Doug Woodby.
So, where were all the coral “gardens”?
The lack of diversity in deeper regions was a surprise, said Stone. Based on previous finds in the North Atlantic and on undersea volcanoes in the Gulf of Alaska, researchers thought they’d see more of the kind of diverse coral habitat they’d found at shallower depths. But even when they did find the same species, the corals found at depths of 1,400 meters and below were often smaller than their counterparts in shallow water. And they represented only a few dominant species.
There appeared to be plenty of food available, sufficient current to deliver the food to the corals, and the lack of sunlight should not be a factor. So why weren’t varied communities of corals thriving there?
One contributing factor, Stone speculated, could be an unstable Aleutian seafloor, subject to frequent earthquake activity. Corals live hundreds of years and need stable rock holdfasts to cling to as they grow.
“Because these are very longlived animals, they need a stable environment in which to live,” Stone said. In some cases, researchers have even seen evidence of landslides.
Other factors could be oceanography and geology, including the types of rocks that are found in different depth zones.
The new finds are intriguing researchers as well as helping them to answer questions already on the table.
Anchorage science writer Sonya Senkowsky is the editor of Alaska Science Outreach (www.alaskascienceoutreach.com). She spent two weeks aboard the R/V Roger Revelle (July 24-Aug. 8) with a team of coral researchers; her time aboard was supported by the North Pacific Research Board and the NOAA Undersea Research Program.