Day 2 – Recovering the benthic elevator
July 10, 2010
1030 hours - On station 30 miles north of Station M The goal of the day was to recover the long-deployed benthic elevator and, in the process, test the tether on the remotely operated vehicle Doc Ricketts. An "elevator" is useful for getting instruments and equipment to the seafloor without having to load it onto an ROV, perfect for large or heavy equipment. Sometimes the equipment remains on the elevator for the duration of an experiment as long as several months; other times the equipment is transported to the seafloor by elevator, then removed from the elevator frame and installed on the seafloor for the experiments. The elevator is dropped from the ship, with sufficient weight to send it to the bottom. When it is time to retrieve the equipment, the ROV is sent down to release the weights and the entire elevator floats to the surface. 
Crew members Dan Benvenuti, Pat Duffy, and Perry Shoemake recover the benthic elevator.
Unfortunately, when the elevator was dropped to the seafloor in May, rough weather and a kink in the ROV tether prevented the ROV from ever reaching the seafloor to place the benthic respirometers on the seafloor and put animals into the respirometer chambers to begin the experiment. Since then, 800 meters were cut from the tether and the tether was reterminated. With the shorter tether, the pilots carefully watched how much they had left as the ROV neared the seafloor. As you can see in the picture below, there wasn't much left on the large drum when the vehicle hit bottom, just shy of 4,000 meters. But the tether worked just fine and the ROV made it to the bottom and back to the surface without incident. 
ROV pilot Buzz Scott had a rare chance to clean off almost to the end of the tether when only a few turns of the tether remained on the drum as the ROV reached bottom.
The Brewer lab group used the day to prepare for tomorrow's dive, which will involve respiration studies on midwater animals. We are sailing overnight to the Santa Barbara Basin, a known low-oxygen zone and therefore a good site for this experiment because animals there are already adapted to the low oxygen waters. Brewer will investigate how they react to increased levels of CO2, to simulate the ocean of the future. The plan is to capture a midwater animal, preferably a squid, in a clear container (called a detritus sampler) attached to the ROV, then slowly inject CO2-enriched seawater into the container and monitor the animal's respiration. At what level of CO2 does the animal become stressed? Senior Research Specialist Ed Peltzer and Summer Intern Melissa Luna calibrated pH sensors and Senior Research Technician Peter Walz worked late into the evening to attach all the necessary equipment to the ROV to be ready for the morning's dive. Postdoctoral Fellow Andreas Hofmann created the computer models that will be used to evaluate the data collected in these experiments. —Nancy Barr >
Visiting scientist Xin Zhang helps clean the benthic respiration chambers that were recovered after two months on the seafloor.
Ed Peltzer prepares pH buffers, used to calibrate the pH sensors for the next day’s experiments.
And finally, the follow up to yesterday’s photo of the Styrofoam cups; all the decorated cups started like one of the white cups at left, before shrinking from the pressure of the deep sea today.
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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.
By bouncing a specially tuned laser beam off of almost any object or substance—solid, liquid, or gas—a laser Raman spectrometer can provide information about that object's chemical composition and molecular structure.
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.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.
A CTD rosette is a cylindrical frame holding a group of plastic water-sampling tubes. Attached to this frame are instruments for measuring water temperature and conductivity (salinity) at various depths. Also attached to the rosette are instruments for measuring parameters such as chlorophyll, nutrients, and particulate matter in the water. As the frame is lowered over the side of a ship, water samples are taken automatically at various depths. Then the frame is raised to the surface again. Research Team
Peter has taken part in more than 30 deep-sea cruises, and has served as chief scientist on major expeditions and on more than 90 ROV dives with MBARI ships and vehicles. His research interests include the ocean geochemistry of the greenhouse gases. He has devised novel techniques both for measurement and for extracting the oceanic signatures of global change. At MBARI his current interests include the geochemistry of gas hydrates, and the evolution of the oceanic fossil fuel CO2 signal. He has developed novel techniques for deep ocean laser Raman spectroscopy, and for testing the principles and impacts of deep ocean CO2 injection.
Ed is an ocean chemist who has been with MBARI since 1997. He has been involved in developing instrumentation and analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has also collaborated on the development of new instrumentation for the measurement of temperature and pH from an ROV. As the group's project manager, Ed is also responsible for expedition planning and logistics.
Peter has worked as a research technician for a variety of scientists at MBARI. Most recently he has supported the research efforts of Dr. Peter Brewer and his interests in the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter assists with the design, testing and deployment of the ocean going science hardware and works closely with the marine operations group to integrate new equipment to work with MBARI's ROV's.
Andreas is a MBARI Postdoctoral Fellow in the Brewer lab. He obtained a PhD in marine biogeochemistry in the Netherlands after his biology undergraduate and bioinformatics graduate studies in Germany. Andreas' specialty is pelagic and benthic biogeochemical modeling with a focus on pH and proton cycling. At MBARI, Andreas is working on the relation between pH and soundspeed, the characterization of marine "dead zones", the development of a sediment model to estimate biogeochemical rates from pore-water methane profiles obtained with the group's deep sea sediment Raman Probe, and on a few other related topics. On this cruise, Andreas will be involved in experiments using the mid-water CO2 and O2 control system and the sediment Raman probe, as well as in various data processing tasks.
Melissa is an MBARI 2010 Summer Intern working in the Brewer lab. She is a graduate of College of Charleston in Charleston, South Carolina with a BS in Chemistry. This summer Melissa will be working on using laser Raman techniques to examine hydrogen sulfide and bisulfide signals as a function of pH in marine pore waters in sea floor sediments.
Nancy manages the editing, design, and production of the MBARI annual report and participates in a variety of editorial and communication projects. She also oversees the institute website. Nancy has been to sea with several MBARI research groups, helping them to carefully remove worms from whale bones, annotate video, sift seafloor sediment, and collect and process water samples. For this expedition she will be in charge of the daily reports that will be posted to this website and will assist with other science crew tasks.
Xin Zhang is a former MBARI student of Peter Brewer and Bill Kirkwood. He was involved in the development of a Deep-Sea Raman Probe for the measurement of sediment pore-water geochemistry.
Zeng Zhigang's research interests are in hydrothermal vents, geochemistry, economic geology, and the exploration of geology and mineral resources. He is on this expedition to learn more about MBARI's tools and methods for study ocean chemistry. |
