|
The Wall, the Wave, and the Weird
Line Up and Be Counted
One of the most interesting sights was the fields of Plumarella soft corals all oriented perpendicular to the
current - a foraging strategy.
Wall Studded with Rockfish
A memorable dive occurred along a wall about 15 meters tall, 500 meters long and 100 meters wide, that held a
remarkable diversity of fish and invertebrates including numerous large rockfish of several species, many with
fat bellies - perhaps gravid (pregnant) females? The wall was riddled with burrows but it was difficult to tell
what organisms inhabited them. Squat lobsters, other crustaceans and brittle stars could be seen in some but
there were thousands of burrows along the wall. It would be fascinating to identify the occupants and what
organism actually creates the burrows.
One of the more unusual organisms on the wall was a pom pom anemone
(Liponema brevicornis) atop a small ledge. This is a very large, pink anemone that looks just like the common
name, a pom pom. Unlike other anemones, its mouth (oral disk) is underneath it and the pom pom anemone is not
attached. Instead, this anemone is like tumbleweed. After seeing our first one on the wall we saw two more
at another dive site on a muddy bottom. A lingcod swam by and the currents caused by its undulations flipped
one of the pom pom anemones over so we could see its oral disk. Within seconds it had righted itself.
Corals as Shark Egg Case Habitat
One of the scientists on board, Peter Etnoyer, has documented the occurrence of shark egg cases on octocorals
in the Gulf of Mexico*. He was excited to see shark egg cases on several
species of gorgonians in OCNMS, including Plumarella, and Primnoa. Corals provide habitat not only for
rockfish, but also for sharks and a multitude of invertebrates. One Paragorgia colony had so many organisms
using it as habitat that instead of standing erect it was bent over clear to the seafloor.
In addition to a
Gorgonocephalus basket star and several Florometra crinoids, shrimp and brittle stars, there were more than
ten shark egg cases attached to the colony - and at least parts of the colony were still alive with feeding
polyps extended. We collected several of the egg cases to try to confirm the shark species. One of the
sharks "hatched" after we collected it.
*Etnoyer, P. and J. Warrenchuk. In Review. On the occurrence of a catshark
nursery in an octocoral field in the Gulf of Mexico. Bulletin of Marine
Science.
Dumbo and Other Canyon Critters
We had one canyon dive, and only into the head of the canyon, so not at its deepest point. We dove to about
650 meters depth in the head of the Juan de Fuca Canyon. Even at this slightly deeper depth however, the
organisms we saw looked different than many seen in shallower waters.
Take a look at the space age shrimp,
Eualus sp., likely Eualus
macrophthalmus,
the beautiful soft coral sea pen Umbellula,
the question mark sea pen (possibly Anthoptilum
grandiflorum)
and the purple sea pen that often has a large brittle star
(Asteronyx loveni) associated with
it.
All of us enjoyed the find of the relatively uncommon and adorable Dumbo octopus
(Opisthoteuthis,
probably O. californiana), a cirrate octopus with muscular lateral fins to propel it. See a video of the dumbo octopus.
Cold Seeps
Cold seeps are ocean floor "springs" where sulfide- or methane-rich fluids are released from the seafloor. We
have known that there are cold seeps in the sanctuary but we had never seen one, and those we know of are in
relatively shallow waters. We were not expecting to come across one on the canyon wall at about 500 meters
depth. Cold seeps look like patches of black sediment or bacterial mats with white precipitate from which a
fluid plume rises. Chemosynthetic communities are sometimes associated with cold seeps. We could see clams on
the surface of the seeps and along the edges whelks, sea stars and on one, a bright purple coral,
identified as Anthomastus cf. ritteri.
We are not sure if any of the organisms we observed rely on the chemical energy
from the seafloor to promote bacterial growth that they can feed upon. We collected some of the bivalves and
a suction sample from one of the seeps to try to find out. It may be that the organisms we saw utilize a
variety of habitats in the sanctuary - certainly some of the organisms near the seeps were seen elsewhere, not
strictly at the cold seeps.
Fine Coat of Silt and an Understory of Hydroids
The movement of the North American continental plate colliding with the Juan de Fuca oceanic plate makes the
sanctuary seafloor a very active place. In addition, sediment from the Strait of Juan de Fuca and the
Columbia River is continually deposited in the sanctuary, covering the seafloor with a fine coating of silt.
The sediments are strikingly evident in the canyons, which trap sediments from the Columbia River (Quinault
Canyon) and the Strait of Juan de Fuca (Juan de Fuca and Nitinat canyons).
The canyon walls we observed were
coated in fine silt. Depending on currents and disturbance levels, hard substrates support "undergrowth" of
hydroids and other moss-like organisms. Corals, especially those in the sea pen family, occur on soft
sediments. At least five species of sea pens were seen on the 2006 cruise. In some areas we observed
step-like benches on the canyon walls, the result of erosion and collapse of the canyon sidewalls. We observed
this type of feature in 2004 in the Nitinat Canyon and on this cruise in the Juan de Fuca Canyon.
|
