Day 6 – Watching the siphonophore migration
June 18, 2011
Location:
Monterey Canyon We began the dive today at 0630, but the siphonophores were up before us. Nanomia bijuga is a common siphonophore in Monterey Bay and many other places around the world. Each day in the late afternoon, these siphonophores undertake a migration, moving up to more plankton-rich, shallow water. Then, early the following morning they begin their return to deeper depths, often trailing krill (which also migrate daily). Today we caught the beginning of that migration with an EK500 echosounder. 
The yellow band in the figure above comes from sound reflected back from the float or pneumatocyst of the siphonophore, Nanomia bijuga as they move from shallow (~100 meters) water down to ~200 meters. Many fishes, crustaceans and jellies make this mass migration on a daily basis, many of them moving several hundred meters.
The plan was to dive to almost 3,000 meters deep in order to observe and collect the little-studied animals living in the water column. We were all looking forward to the dive because weather has, until now, kept us from our deeper study sites. Segmented and bioluminescent polychaete worms, nemerteans, and munnopsid isopods affectionately called "spiders" were high on the list for Dr. Karen Osborn, a visiting scientist from the Smithsonian Institution. But even below the oxygen minimum zone (see yesterday’s post), where oxygen begins to increase again, we saw very few animals. Our enthusiasm began to ebb. Then at 1,600 meters, when we saw the swimming tongue. Completely orange, this nemertean was at least the size of a large tongue-depressor. Another nemertean we collected later was actually brooding its young on its back! This was definitely a jaw-dropper; especially for Karen. 
Nemerteans are neither worms nor fish, although they look a bit like both. They are unique enough to belong in their own phylum.
Over the course of the dive we added two undescribed species of "spider", and a medusa in the genus, Chromatonema that we’ve only seen once before. The bathypelagic (deep open) ocean comprises a tremendously large habitat in the world ocean, extending from ~ 2,000 to 4,500 meter depths. Dr. Bruce Robison and the rest of us in the midwater lab are very interested in bathypelagic biodiversity and, while we learn a tremendous amount with each dive we make, we have only scratched the surface. 
Munnopsid isopods aren’t spiders at all, but you can see how they got the name!
As the ROV Doc Ricketts ascends with our samplers full and video of behaviors that give us insight into how these animals make their living, I am amazed that we once thought the deep sea devoid of life. Only after putting the animals into our cold room, did I remember the mesh bags filled with styrofoam cups that we had attached to the ROV prior to the dive. My son, Kieran, his fellow pre-schoolers from Ms. Barbara’s Child Development Center and many MBARIans decorated styrofoam cups and gave them to us to shrink. Since pressure acts equally on all sides of a submerged object, things with small air spaces, like styrofoam, shrink uniformly and return from the depths miniature versions of the original. At 3,000 meters there is over 300 atmospheres of pressure and these cups looked tiny … and great! 
Please come by our open house in Moss Landing (Saturday, June 25th) to learn more about MBARI and the science we do… and there might even be a shrunken cup for you! - Rob Sherlock
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Logbook
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Equipment
 R/V Western FlyerThe 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 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.
The MRS conducts oxygen consumption rate measurements in situ gauging the metabolism of animals without subjecting them to the stresses of transport to the surface. MRS has been modified to operate in deeper water with an expanded capacity, enabling respiration studies on animals that live deeper than 1,250 meters.
Detritus samplers are large plexiglass containers with lids that can be controlled by the pilot of the ROV and gently closed once an organism is trapped inside.
The CTDO is mounted on the ROV and takes in situ measurements of environmental parameters such as conductivity, temperature, depth, and oxygen concentration.
This sampler acts like a vacuum cleaner sucking up samples and depositing them into one of the 12 buckets. Research Team
Bruce Robison's research is focused on the biology and ecology of deep-sea animals, particularly those that inhabit the oceanic water column. He pioneered the use of undersea vehicles for these studies and he led the first team of scientists trained as research submersible pilots. At MBARI, his research group has focused on the development of remotely operated vehicles as platforms for deep-sea science.
Kim's general area of interest is the study of midwater and deep sea animals. He has developed many tools and techniques to observe, manipulate, and collect these organisms, and to maintain the animals in the lab.
Rob studies the properties and organisms of the ocean's largest habitat, the midwater. His research group is learning more about the ecology of midwater organisms; their abundance and seasonal patterns, depth ranges and who eats whom. Rob enjoys watching mesopelagic animals with the HD (high definition) camera; animals that once would have come up as glop in a net can be seen to have delicate structure and complex behavior (e.g., squid inking or changing color, fish eyes that rotate to keep prey in sight, an amphipod carving up a pyrosome to make a home).
Kris works with the Midwater Ecology group, analyzing ROV video transects between 50 and 1,000 meters in depth to identify biological organisms from all taxonomic levels, most of which spend their entire lives in the oceanic water column. Kris started working at MBARI in 1996 after finishing her Master's at UC Santa Cruz. She's looking forward to returning to sea this month to collect video transects and search for deep-sea lobster larvae from the family Polychelidae.
Susan works in the MBARI video lab, where her primary responsibility is to watch video taken with MBARI's remotely operated vehicles (ROVs) and make observations about the organisms, behaviors, equipment, and geological features that she sees. While annotating video, she's become adept at identifying numerous deep-sea organisms, specializing in midwater organisms. She works closely with the midwater ecology group and the bioluminescence lab to expand her knowledge of the fish, jellies, cephalopods, and other groups in the midwater.
Henk-Jan received his Ph.D in Ocean Ecosystems from the University of Groningen. Henk-Jan has developed an experimental program of both laboratory and in situ research that will chemically mark increments in the deposition of squid statoliths. Using the marks as temporal reference points, the pattern of deposition should allow him to determine the age of any squid.
Karen's research interests include evolution of pelagic life, phylogenetics of marine invertebrates, and mechanisms of speciation in the open ocean and the deep sea. Karen is a former MBARI graduate research assistant and is currently a University of California President's Postdoctoral Fellow at Scripps.
Richard is Professor Emeritus of Oceanography at the University of Hawaii. His research seeks to increase our understanding of cephalopod phylogeny and biodiversity, focusing in particular on cephalopod beaks, one of the more under appreciated features of all cephalopods, and their potential usefulness in phylogeny and identification.
Alexis is working with the Midwater Ecology Lab as a summer intern. Her interest in deep sea research has brought her to MBARI from UC Santa Cruz where she received her B.S. in marine biology, and more recently worked as a research technician. |
