Day 8 — NESCA (Northern Escanaba Trough), southern Gorda Ridge
September 5, 2009
Latitude 41 degrees 0.47 minutes N
Longitude 127 degrees 29.59 minutes W
Weather chased us south again, and we are now diving at the Escanaba Trough, the southern-most segment of the Gorda mid-ocean ridge. The axial valley here was deluged with sediment from the Missoula Floods in the Pleistocene. The glacial Missoula Lake in western Montana breached its moraine dam numerous times, sending floodwaters across eastern Washington (forming the "Scablands"), through the Columbia River drainage (carving the Columbia Gorge), out across the continental shelf and abyssal plain (cutting channels still visible in seafloor bathymetry), against the Mendocino Escarpment, and back north into the Escanaba Trough, filling it with half a kilometer of turbidite mud and sand of continental origin.
Since then, a single volcanic eruption has occurred in the area. Intrusion of lava sills lifted large hills of the sediment, and hydrothermal fluids vented through the faults and organic-rich mud, growing sulfide chimneys that have long-since extinguished and crumbled. The sulfide-rich deposits now feed communities of vesicomyid clams. We sampled several patches of those clams today for genetic comparison with clams from other hydrothermal and cold-seep locations. Patrick, our steward, prepared a delicious Manhattan Clam Chowder for lunch today, in honor of the occasion.
Crumbling sulfide outcrops and mud provide an energy source for this community of vesicomyid clams, anemones, and galatheid crabs.
On Doc Ricketts dive 83, we returned to clam beds in altered sulfide deposits observed on a dive in 2005. We collected nearly 50 clams from five distinct patches (separated by tens to hundreds of meters) for our population genetic studies. These are relatively large (exceeding 30 centimeters in length) organisms that have sulfur-oxidizing bacteria living within the cells of their gills. This fascinating example of endosymbiosis allows these clams to make a living by exploiting sulfide-rich sediments at over 3,000 meters depth, where they play an ecologically central role in the deep-sea community. The majority of the clams we encountered appear to be the long, narrow species Ectenagena extenta. Standing on end, these clams use their prodigous length to span the oxidation-reduction zone between the sea water and sulfide-rich sediments tens of centimeters deep. E. extenta (like other vesicomyid clam species) absorb sulfides from the anoxic mud and circulate them through their tissues up in the oxic zone, thereby making the compounds available to sulfur-oxidizing Gammaproteobacteria living in their gills. The bacteria, in turn, supply the clams with nutritive energy. Five much smaller clams, with darker shells, more ovate than elongate, were buried within the mud and were collected coincidentally as the ROV crew filled our clam scoop with the much more visible E. extenta. These smaller clams are almost certainly hosting endosymbiotic bacteria as well, although which kind and in which tissues we have yet to determine.
In addition to housing the bacteria inside, large numbers of sea anemones were perched on the exposed end of each clam. Places for attached organisms to live are known to be ecologically limiting in crowded near-shore marine environments—here we can see a similar situation in a deep-sea benthic habitat. Although it is uncertain whether or not these anemones derive some kind of nutritive benefit from their clam substrates (such as from effluent released by the clams), every clam hosted up to 18 anemones of all sizes. Whether by acting as a substrate for other organisms, or by 'farming' intracellular bacteria to turn chemical energy into their own biomass, these clams are ecologically valuable members of an incredibly diverse, sporadic, island-like benthic community, in one of the deeper places on earth.
A stunning example of Ectenagena extenta, situated in a small group of individuals within the larger clam bed, as seems to be their habit. The clams are festooned with beautifully tentacled anemones. Each clam lives half-buried, with its foot down in the sulfide-rich mud and its gills up in the oxygenated seawater. By housing sulfophilic bacteria in their gills, these clams, like many similar organisms living at deep-sea hydrothermal vents, seeps, and other even more ephemeral nutrition sources, can turn chemical reducing power across reduction-oxidation gradients into biomass. The red dots are lasers set 29 centimeters apart for scale.
We have reached and gone past the midpoint of our voyage and it doesn’t seem like the number of new or rare sea stars has gone down. The many kinds of marine animals which live in this part of the North Pacific are, at best, poorly known and so the rate of discovery is fairly high. But there is one particular family, the Goniasteridae, that seems to outnumber all the others.
Goniasterids are fairly distinctive, having a heavily calcified body with a prominent border surrounding the edge of the animal and often a skeleton composed of linearly arranged plates. There are more goniasterid genera (about 80) and species (~200) than almost any other single family of asteroids and amazingly, new species are still being found. In fact, the great majority of the new species I encounter are often goniasterids. I have already written about some goniasterids, the coral predator Evoplosoma, for example. But many goniasterids don’t really stand out unless you stop and take a look at them. Such has been the case on our trip!
When the ROV flies over muddy bottoms, many small, white, pentagonal sea stars are frequently observed which would be passed by many folk. But I’ve made a concerted effort to stop and pick up these nondescript, white to orange stars. Already, I’ve found what seem to be at least three new genera and tentatively another four new or rarely encountered species. Goniasterids are diverse. Some, such as the frequently seen Mediaster, occur widely around the world in shallow waters as well as in deep-sea environments. Observations suggest Mediaster stars live on sediment and are peaceful deposit feeders or possibly just scavengers. A relatively modest feeding mode relative to the highly specialized Evoplosoma, which feeds on deep-sea corals!
To add to our growing list of goniasterids is a new genus and species discovered crawling through a field of dead (center) and living (right) clams. It's not nearly as fancy as some of the new species I’ve described but who knows how its importance may factor into a greater ecological picture someday!
Members of the ship's crew practice handling a fire hose during the weekly fire and boat drill.
The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
R/V Zephyr is the primary support vessel for MBARI's autonomous underwater vehicle (AUV) program. This 26-meter vessel is also used to maintain environmental moorings, collect time-series data along the California Current, and support scuba divers as they study near-shore habitats.
AUV D. Allan B.
The MBARI Mapping AUV is a torpedo-shaped vehicle equipped with four mapping sonars that operate simultaneously during a mission. The multibeam sonar produces high-resolution bathymetry (analogous to topography on land), the sidescan sonars produce imagery based on the intensity of the sound energy's reflections, and the subbottom profiler penetrates sediments on the seafloor, allowing the detection of layers within the sediments, faults, and depth to the basement rock.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using ROV Tiburon's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Niskin bottles are used to collect water samples as well as the tiny bacteria and plankton in that volume. The caps at both ends are open until the bottles are tripped, when the caps snap closed.
The box fits in a partition in the sample drawer. It is shown open, with an animal being placed into it by the ROV's manipulator. When the lid is closed, the box will hold water to protect the animals inside.
This device is used to collect volcanic glass fragments from the surface of a flow. It is made of about 450kg of lead and steel and is launched over the stern of the ship on a wire. Fragments of rock that break off of the lava flow on impact are trapped in wax-tipped cones mounted around the crusher. The wax is melted in the lab to liberate the rock particles for analysis.
Sample drawer with partitions
The benthic toolsled is attached to the bottom of the ROV for our geology dives. Its components are the manipulator arm and the sample drawer. The sample drawer is shown open on deck, full of rocks. Normally it is closed when the vehicle is operating and is opened only when a sample needs to be stowed. Partitions in the drawer help us keep the rocks in order. The rocks often look alike, but the conditions and chemistries of the eruptions are different so it is important that we know where each came from.
Glass suction sampler
This equipment is used to vacuum glass particles and larval animals from cracks and crevices. The carousel of small plastic jars fitted with wire mesh will be mounted in the benthic toolsled. The hose will be held by the ROV's manipulator and a suction will be drawn by the pump.
Canvas bags on a T-handle for collecting gravel or other materials that fall out of a push-core.
Held by the ROV's manipulator, the wire on the right is placed into the fluid emitted from a hydrothermal vent to record the temperature.
Senior Scientist, MBARI
Dave's research interests are nearly all related to the formation and degradation of oceanic volcanoes, particularly Hawaiian volcanoes, mid-ocean ridges, and isolated seamounts. Topics of interest include: compositions of mantle sources for basaltic magmas and conditions of melting; volatile and rare-gas components in basaltic magmas and their degassing history; chronostratigraphic studies of eruption sequence and evolution of lava chemistry during volcano growth; subsidence of ocean volcanoes and its related crustal flexure, plate deformation, and magmatic activity; geologic setting of hydrothermal activity; origin of isolated seamounts; and monitoring of magmatic, tectonic, and hydrothermal activity at submarine and subaerial volcanoes.
Senior Research Technician, MBARI
Jenny works with Dave Clague in the Submarine Volcanism project. On this expedition, Jenny will be in charge of the GIS work, including use of the recently acquired, high-resolution MBARI Mapping AUV data of our dive sites. She will also stand watches in the ROV control room, help with rock and sediment sample workup and curation once the vehicle is on deck, and coordinate these cruise logs for our group's two legs of the expedition. She is now quite solidly a marine geologist, but her degrees are in biochemistry (Smith College) and biological oceanography (Oregon State University). She is thankful for the opportunities that have led her to study volcanoes, and loves being involved with the research and going to sea. She looks forward to discovering more about how the Earth works.
Science Postdoctoral Fellow, MBARI
Brian completed his Ph.D. in igneous geochemistry at Washington University in Saint Louis in 2007 and has since been working in MBARI's Submarine Volcanism Group. Brian applies the principles of isotope geochemistry to young samples of volcanic rocks to gain insight into aspects of magmatism. Much of his postdoctoral work focuses on eruption and petrogenetic timescales of Axial Seamount, the most volcanically active portion of the Juan de Fuca Ridge. His other research interests include geochemistry of the Earth's mantle, magmatic interaction between oceanic spreading centers and hotspots, and exploiting the systematics of rare isotope species to quantify material flux through subduction zones.
Assistant Director of Science, National Evolutionary Synthesis Center
Craig has conducted deep-sea research for 11 years and published over 30 papers in the area. Participation in dozens of expeditions has taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig's research focuses on the ecological and evolutionary drivers of marine invertebrate biodiversity and body size. He is the author and editor of Deep-Sea News, a popular deep-sea themed blog and rated as the number one ocean blog on the web, and his popular writing has been featured in Cosmos, Science Illustrated, and Open Lab: The Best Science Writing on the Web.
Senior Research Technician, MBARI
Linda specializes in the ecology of small animals that live in marine sediments (macrofauna), and larger invertebrates and fishes that live on the seafloor or just above it (megafauna). She conducts habitat characterization studies in benthic (seafloor) ecosystems using underwater video and by collecting deep-sea animals. She hopes to find some new and interesting animals in the unique habitats we are visiting on this cruise.
Postdoctoral Fellow, University of Sydney
Angel is a carbonate sedimentologist specialist in non-tropical carbonate sediments. His current research, however, is focused on the tropical realm. He is working on drowned reefs from Hawaii, studying their morphology and structure, sedimentary facies and stratigraphical successions in order to attempt to constraint eustatic sea-level changes, subsidence rates, drowning times, carbonate accretion rates, and paleobathymetry. In this expedition Angel hopes to learn basic skills in marine geology that could help him to better understand the data he works with in his current research.
Research Technician, MBARI
Julio is a molecular ecologist and evolutionary biologist currently working on the population genetics of various deep-sea invertebrate species in Bob Vrijenhoek's laboratory. Julio is also developing molecular probes capable of detecting a variety of marine invertebrate larvae and other microorganisms from environmental seawater samples as part of the Environmental Sample Processor project.
Research Collaborator, Smithsonian Institution
Chris specializes in the evolution, systematics, and taxonomy of echinoderms, specifically asteroids (starfish or sea stars). His research emphasizes cold-water species, including those living in the deep sea and at high-latitudes (Antarctica and the Arctic). He has identified starfish species for National Geographic, the National Marine Fisheries Service, and MBARI, as well as organizations in France, Australia, Palau, and New Zealand. He has been on many deep-sea cruises, including submersible work in the Bahamas and Hawaii as well as more conventional scientific cruises in Antarctica, Alaska, as well as off Monterey, California. He is also the author of the Echinoblog, an echinoderm-themed blog. This will be his first trip on the Western Flyer.
Soureya recently received her bachelor's degree in general geology in Munich. She gained field experience related to volcanology during a campaign to Colima volcano in Mexico, where she looked at pyroclastic flow and block-and-ash flow deposits, did detailed stratigraphic logs, and performed density measurements in the field. She also participated in a field trip to Etna, Vulcano, Lipari, and Stromboli volcanoes where she was shown the different aspects of Italian volcanism. After these terrestrial experiences she is now looking forward to discovering more about submarine volcanism. She will benefit greatly from participating in this cruise, as it is highly complementary to her university education.
Student, University of Quebec, Chicoutimi
Levin Castillo-Guimond finished a BSc-Honour's degree in Earth Sciences at University of Quebec in Chicoutimi (UQAC-2009). His prime interest was on the physical volcanology of Archean mafic and felsic submarine successions, as they are often associated with volcanic massive sulfide deposits (VMS). In addition, to better understand large-scale caldera evolution and pyroclastic processes, Levin participated on a field trip in autumn 2007 on the island of Tenerife (Canary Islands). In summer 2009 he worked for an exploration focusing on gold and uranium deposits.
Gillian recently received her BSc-Honours degree in Marine Biology in Brisbane, Australia. She gained diving field experience while observing fish behavior on the Great Barrier Reef. On previous research cruises, she has assisted in the processing of collected organisms and in the collection and analysis of underwater video to identify the benthic life present on flows over an age series. On this cruise, she will assist in the collection of underwater video and hydrothermal clams and tubeworms, and aims to gain a better understanding of the diversity of animals living at these sites.