Dariusz Stramski - US grants

*** 9531975 Mitchell This research project is part of the US Joint Global Ocean Flux Study (JGOFS) Southern Ocean Program aimed at (1) a better understanding of the fluxes of carbon, both organic and inorganic, in the Southern Ocean, (2) identifying the physical, ecological, and biogeochemical factors and processes which regulate the magnitude and variability of these fluxes, and (3) placing these fluxes into the context of the contemporary global carbon cycle. The Joint Global Ocean Flux Study (JGOFS) has had three successful field efforts (in the North Atlantic, equatorial Pacific, and the Arabian Sea), and the last major field effort will be in the Southern Ocean. The overall objectives of JGOFS are to determine and understand processes controlling the time-varying fluxes of carbon and associated biogenic elements, and to predict the response of marine biogeochemical processes to climatic change. The Southern Ocean is critical in the global carbon cycle, as judged by its size and the physical processes which occur in it (e.g. deep and intermediate water formation), but its present quantitative role is uncertain. This project concerns the development of relationships between the optical properties of sea water and the concentrations of carbon-based biological parameters such as phytoplankton pigments, particulate organic carbon, and the formation and export of organic carbon from the upper layers of the ocean. The objectives are both to investigate biochemical processes in the low stability Southern Ocean environment, and to develop algorithms for the interpretation of remotely sensed ocean color images. The in situ data will be obtained from an instrumented ocean buoy that will provide detailed information on the spectral reflectance, light attenuation, and scattering coefficients in the context of actual process data provided by other investigators in the Southern Ocean Experiment. The information and understanding developed through this project will directly improve our abil ity to extrapolate the time and space scales of the Southern Ocean carbon flux system, and allow the development of more accurate system models and the interpretation of long-term changes in the ecosystem.

ABSTRACT

OCE-0324680 / OCE-0324346

In this research project, investigators from the Scripps Institution of Oceanography and University of Southern California will work to establish bio-optical relationships for deriving particulate organic carbon (POC) concentration in the ocean from optical measurements. These relationships will be applicable to data collected from ships, unattended moorings, drifters, and satellite ocean color sensors. The approach to be taken is based on the use of historical in situ data collected by various researchers. Over the years, extensive bio-optical data have been collected in various regions of the world's ocean, which are now available through JGOFS and NASA's SeaBASS databases. These and other historical data sets will be reanalyzed to derive optical relationships for studying the POC dynamics in the ocean. It is expected that by taking a full advantage of the already collected data, a substantial progress in this area will be made. The research team will interact with several researchers who generated basic data that will be used in this project, and these contacts will also ensure that all related research efforts will be well coordinated.

The project us expected to provide important scientific contributions to our understanding of the ocean reservoir of POC and its role in ocean carbon cycle. The project builds on significant science questions and unexplored opportunities for the application of optical techniques to the study of POC in the ocean. Optical measurements have already proven to be a major device for studying chlorophyll a and primary production on regional, basin, and global scales. However, the major currency of interest for understanding ocean biogeochemistry is carbon, not chlorophyll a. The impact of the proposed work stems from the fact that the combination of bio-optical relationships with new technologies (satellite sensors, unattended in situ platforms) will provide a capability to acquire information about POC in the ocean on previously impossible scales of time and space. The proposed project is a step towards a long-term research goal, which is to apply the bio-optical algorithms to the global ocean color data in order to study POC dynamics on synoptic, seasonal, and interannual time scales.

The project has a number of broader impacts. Among them, it will represent a major component of the Ph.D. research of a graduate student. Moreover, the investigators will create project-specific websites with the compiled data and results, which will be specially designed both for the science community and general public.

P.I. Papen, George Proposal #: 0428900

Project Summary
Nanoparticles, or colloids in aquatic environments, have sizes ranging from 1 to 1000 nm and are at the boundary between soluble chemical species and sinking particles. They are the most abundant particles in the ocean and other aquatic environments and account for a significant portion of "dissolved" organic carbon. In situ characterization of the physical and biochemical properties is crucial for a wide range of fundamental applications including: 1) ocean biogeochemistry 2) ocean optics and 3) aquatic biological hazards.

While the characteristics of nanoparticles are important for a variety of applications, their complex heterogeneous nature and small size makes the in situ determination of their physical and chemical characteristics extremely challenging. To date, most characterization techniques are laboratory-based and are thus limited. This project will develop in situ sensor networks for aquatic nanoparticle characterization that can address a broader range of applications and test them in an ocean environment. The research program consists of the development of microfluidic-based techniques that can preprocess and help analyze heterogeneous assemblies of aquatic nanoparticles and bacteria and the development of a pipelined suite of advanced optical techniques using the amplitude and the phase of the optical fields, multiple wavelengths, multiple scattering angles, polarization properties, and parallel interrogation volumes, which sequentially classify particle characteristics over a wide range of variables. The program will culminate in the deployment of a prototype in situ sensor network node that can measure both the physical and biogeochemical properties of aquatic nanoparticles forming the basis of a complete sensor network for in situ spatial and temporal monitoring.

Colloids are the most abundant particles in the ocean and other aquatic environments, and play a crucial role in the structure and functioning of these ecosystems. The PI's request funding to design and fabricate a new instrument, an Aquatic Colloidal Analyzer (ACAN), for quantitative determinations of concentration and size distribution of heterogeneous colloidal assemblages (including nanoparticles) present in aqueous suspensions. No instrumentation is presently available which provides accurate information about size distribution of polydisperse systems of aquatic colloids over a broad size range from about 10 nm to 1 µm. The ACAN will utilize a Nanoparticle Tracking Analysis (NTA) method, which is based on physical principles of Brownian motion and light scattering by colloids.

The ACAN measurements on unperturbed samples will provide a capability for acquiring an unprecedented wealth of scientifically new and valuable information on polydisperse assemblages of naturally occurring aquatic colloids, which cannot be obtained using present techniques. The data from these measurements will be fundamental in extending the understanding of the biogeochemistry of the ocean, the carbon cycle, satellite remote sensing of the oceans for biogeochemical and climate studies, the roles of microbes in ocean ecosystems, and atmospheric colloidal particles and their deposition into the ocean (via rainwater analysis).

Broader Impacts:

The proposed instrument has the potential to impact a broad range of environmental studies related to particle dynamics, such as biology, chemistry, optics, physics and climate science. These measurement are critical for many fields in the aquatic sciences The project would interface with the education and outreach projects with the UCSD Preuss School and the Scripps Birch Aquarium designed for K-12 students, college students, and general public.

The PI and his group have developed an innovative technology named Multi-spectral Apparatus for Nanoparticle Tracking Analysis (MANTA) for accurate characterization of nanoparticle concentrations and sizes in an unperturbed state, which is relevant for many applications and research areas; for instance medical, pharmaceutical, biochemical, physical and environmental. Tests with nanoparticle standards demonstrate that MANTA outperforms existing commercial technologies. The superior performance of MANTA is due to novel approaches including sample illumination and video recording of nanoparticle Brownian motion and to proprietary algorithms and software for analysis of video data. MANTA is capable of providing information on nanoparticles meeting outstanding needs not currently met by the existing technologies and that affects a broad variety of industrial sectors/applications which utilize nanotechnology, such as manufacturing diagnostics, the printing, drilling, and milling industries, and the production of cosmetics, pigments, inks, catalysts, and textiles.

Because measurements of concentration and size distribution of nanoparticles are essential to many applications as stated above, a range of potential customers for MANTA technology is large and diverse with no single typical customer profile. MANTA ensures that the concentration and size of nanoparticles are accurately determined over a broad range of nanoparticle sizes. The innovative solutions of MANTA thus represent a transformative advancement in the area of nanoparticle analysis and a major competitive advantage over existing technologies. The team expects that MANTA will have transformative effects in a broad range of health and environmental applications, including the diagnosis of disease and pathological conditions, development of efficient and specific therapies, environmental risk assessment, food safety, and occupational health and safety risk management strategies.

Low-light conditions in the ocean have critical significance in the lives of marine animals due to various light-dependent physiological mechanisms and behavioral patterns associated with animal vision, communication, reproduction, predation, antipredator tactics, and vertical migration within the water column. Therefore, low-light environments have multiple implications for oceanic habitats, water quality, and commercial fisheries production. Measurements of extremely low-light marine environments including twilight (sunset and sunrise) conditions in the surface ocean layer as well as very dim solar daylight within deeper layers extending from about 200 to 1000 m depth are not possible with existing conventional instruments. As a result, such measurements have been very scarce and greatly limited in scope. The instrument to be developed in this project, called LARS (Low-light Aquatic Radiometer System), will have an unparalleled capability to accurately measure extremely low light, which will pave the way to improved characterization of deep-sea light and twilight conditions in the ocean beyond oversimplifying historical descriptions. This instrument will aid in expanding research of deep-sea habitats to protect the biodiversity and integrity of these largest ecosystems by volume on Earth, an important goal recognized by international community of scientists and policy-makers.

The proposed development of LARS will be based on state-of-the-art highly sensitive photon counting technology which will allow measurements of extremely low levels of underwater spectral irradiance of 10 - 20 photons/(cm2 s nm) within the visible spectral range. This will enable measurements of dim daylight at ocean mesopelagic depths (~200-1000 m) not only of blue light but also, for the first time, potentially biologically significant levels of green and red light generated locally at depth by inelastic radiative processes such as Raman scattering by water molecules. In addition, LARS will provide the capability to measure both the downward and upward irradiances in low-light marine environments, which has never been done before. Field demonstrative data will be collected to comprehensively characterize the deep-sea light field and provide first experimental evidence for the role of inelastic processes and approach to the asymptotic light regime at depth. The measurements of poorly characterized twilight and moonlight conditions in the ocean surface layer will be also demonstrated. The broader utility of LARS will be demonstrated by data analysis in support of the study of specific biological questions related to low-light marine habitats.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.