Guest log by researcher Scott France: Account of a Jason Dive

Tuesday night (July 27) in a shipboard wet lab, researcher Scott France holds a pycnogonid sea spider found on a curlicue-style deepsea whip coral, Radicipes. One of the goals of the coral expedition is to determine the role of deepwater corals as fish and crab habitat. France and colleagues stayed up through the night to preserve and log specimens for later study. Photo by SONYA SENKOWSKY See related images: Late-night labwork Emptying the Biobox

Location: N. Atka Island

Posted 07.29.04 at 7:11 pm

Observations by Scott C. France,
University of Louisiana at Lafayette

Tuesday’s (July 27) Jason II dive largely followed a muddy ridge, with relatively little change in depth. Until the end of the dive, we did not encounter any steep topography, walls, ledges or even outcrops of rocks and boulders—and therefore, saw few of the corals and related organisms we are searching for. 

Most of the gorgonian sea fans and sponges we are looking for require exposed hard bottoms to which they can attach themselves. The communities we encountered Tuesday were soft bottom types.

At the deeper end of the dive (2900 meters) the soft bottom was hummocky due to invertebrates burrowing through the mud.  We saw thousands of spoon worms—or at least, we saw their “spoons,” which are tongue-like proboscises that extend from the burrow while the rest of the body remains buried.  The proboscis can extend more than 100 times the length of the body, and is used to gather food particles from the surface of the bottom. 

We did see one species of octocoral frequently in this area, a sea pen (Pennatulacean) called Umbellula.  Sea pens are corals specialized for living on soft bottoms by anchoring themselves into the sediment with a bulbous, inflatable base. Umbellula has a thin stalk standing almost a meter above the bottom, with a pinwheel arrangement of large polyps—the tentacle-bearing feeding structures of corals—at the top.  They form beautiful and graceful colonies.  Several of the colonies had a pair of red amphipods, small, shrimplike crustaceans, grasping the stalk.  We collected one colony that had a sea anemone attached to the stalk.  This is a common observation in the deep sea:  many invertebrates that capture their food from the water column climb up onto whatever structures they can find in order to get into faster moving currents. We also saw polychaete worms swimming up from the bottom as the ROV approached.

Further along the transect, the muddy bottom became smoother and the community changed to one dominated by two different species of sea pens: one tall, thin one we referred to as a “whip sea-pen,” and a shorter, fleshier species.  Many of the “whip sea-pens” had a brittle star wrapped around them, with the star’s arms drifting with the current.  We collected a couple of colonies with and without brittle stars to determine if the stars were feeding on the sea pens, or simply using them to get up off the bottom. We also saw the occasional sea cucumber and sea urchin, and numerous burrowing sea anemones.

Just before the ROV was to leave bottom, we encountered a small ledge that was inhabited by many sponges, crab and hydrozoans (delicate “bushes” of microscopic sea anemone-like animals).  We also found one of our first gorgonian corals of the day, a curly-cue whip coral in the family Chrysogorgiidae.  We collected a specimen that had a palm-sized sea spider on the stalk, and a chunk of rock from the ledge that had a large sponge on it.

The ROV was recovered at about 11:30 p.m., and that is when my work really began.  I am interested in determining the geographic range the coral species inhabit.  Are the corals we see in the Aleutians the same as those in the Gulf of Alaska or the deep sea around Hawaii and elsewhere in the Pacific (or Atlantic), or are these species unique to this area?  To answer this question, I look at the DNA sequences of the corals.  The DNA analysis is done back in my lab at the University of Louisiana at Lafayette.  Here on the ship, I collect fragments of branches and tissue from which I extract the DNA. 

Our collections Tuesday resulted in nine sea pens, one curly-cue coral, and several sponges.  My colleague Gordon Hendler was very excited about the several brittle stars we collected.  It took us about six hours to complete preserving and processing the samples.  After a few hours’ sleep, we’ll be ready for—and excited about—the next dive!