New tools and techniques for marine science
Principal Investigator: Hans Jannasch
Scientists are becoming increasingly aware that the ocean is a highly variable realm where many cycles are driven by sporadic and short-term events such as storms, upwelling, and phytoplankton blooms. Better knowledge of processes that affect the variability of important chemical compounds in the ocean is essential for improving scientific understanding of the interactions between the seafloor, the ocean environment, and the atmosphere. For example, in many areas of the ocean, levels of phytoplankton productivity are limited by the availability of the nutrient nitrate. In other regions where nitrate is abundant, a lack of iron or phosphate may curb productivity. Drawing carbon dioxide from the atmosphere, via surface waters, phytoplankton sustain ocean food-chains. Thus, deciphering chemical cycles associated with phytoplankton is of great importance. The origins and fates of many other chemicals in the atmosphere, throughout the water column, and at the seafloor are likewise integral to the workings of ocean ecosystems.
This project continues MBARIs long-term efforts to advance the understanding of marine chemical processes through the development of better instruments, systems, and methods. Project tasks are geared to evolving advanced instruments for in situ, continuous, real-time measurements of ocean chemistry. The efforts fall into three main categories:
P6A Ocean biogeochemical processesFocusing on processes affecting the oceanic distribution and cycling of greenhouse gases, notably carbon dioxide and methane, this sub-project encompasses:
P6B Continuing development of in-situ analyzers and samplersThe
success of the in-situ nitrate OsmoAnalyzer,
currently in use on moorings in Hawaii, Bermuda, and the equatorial Pacific, as well as
Monterey Bay, has prompted the adaptation of this relatively low-cost, simple, long-term
monitoring device to other significant chemicals. An OsmoAnalyzer for hydrogen
sulfidea compound of major interest, in part for its role in supporting life at
hydrothermal vents and cold seepsis nearly finished. Similar analyzers for iron and
manganese are also under development. The MBARI chemical analyzer group expects to test
prototypes of the sulfide, iron, and manganese instruments in 1998. A major redesign
effort to simplify the analyzer, improve its duration, and to increase its overall
reliability is currently underway. Due to the significant interest expressed by the
oceanographic community, negotiations are continuing with a potential commercial partner
for transferring the technology to make it generally available.
Refinements on both types of sensors are ongoing, based on the results of field use.
P6C Chemical mapping toolsInstitute scientists and technicians are continuing to refine tools for improving measurements that will help pin down marine chemical processes and identify biogeochemical responses to changes in climate and ocean circulation (see Project 1). Measuring the various forms of carbon in the ocean reveals different aspects of the cycling of this all-important element. A device for determining the partial pressure of carbon dioxidethe difference between atmospheric and oceanic CO2 levelshas been used on MBARI moorings since 1993. Information from this sensor tells whether the ocean is acting as a sink for CO2 or, in areas of strong upwelling, as a CO2 source. Researchers also are using MBARI-originated shipboard systems for continuous sampling of total carbon dioxide, which indicates levels being taken up by photosynthesizing phytoplankton. Similar shipboard techniques are used to sample nitrate and silicate, another important nutrient. Upgrades are planned for the computer software that enables the sampling data to be combined with geographic information to create chemical "maps." In the coming year a dissolved organic carbon analyzer and an alkalinity titrator will be constructed to aid in the study of the oceans carbon system. For ROV use, a methane detector and an in-situ pH probe will be tested. These will allow continuous mapping of methane and pHwhich is sensitive to CO2 concentrationsmaking it possible to conduct directs searches for chemical plumes near the sea-floor.
MBARI chemists also are assembling equipment to synthesize gas hydrates in the laboratory. They will study, among other things, how hydrates "grow" and dissolve, how they react with seawater, and other factors that affect their stability. To assist these studies, existing gas chromatography equipment is undergoing modifications for measuring methane and other light hydrocarbon gases in seawater and sediment samples.
Chemical mapping, lab studies, and increasingly sophisticated measurements of key chemical compounds will contribute important information to modeling mid-latitude, coastal upwelling systems such as that of Monterey Bay.
Next: Feasibility studies
Last updated: 07 October 2004