Project Funding: 2013 - 2015

NRA: 2012 NASA: Ocean Biology and Biogeochemistry   

Funded by NASA

Abstract:
The particulate organic carbon (POC) pool in the surface ocean is a major, dynamic carbon reservoir, and through the biological pump, it provides a means for transfer and potential storage of atmospheric CO2 into the deep ocean. POC (as well as the phytoplankton fraction of POC) is of large interest in biogeochemical studies, in part because of the potential climate impact of changes in the biological pump; however, the variability of POC both regionally and globally is poorly understood due to a lack of direct measurement at sufficient spatial and temporal scales. The availability of high-resolution optical measurements from ocean color remote sensing and in-situ optical instrumentation has stimulated interest in the development of optical POC proxies that allow measurement of POC on temporal and spatial scales that surpass traditional, discrete water sampling methods. POC algorithms are based on both particulate beam attenuation and particulate backscattering coefficients, but both display great variability as a function of geographical regime and/or investigator, leading us to ask the following questions: 1. What are the mechanisms responsible for the observed variability in optical proxy algorithms? Is the variability natural (inherent to the specific ecosystem or regime) or due to methodology (both optical and chemical POC)? 2. If the variability is natural, what are the drivers of the observed variability? We hypothesize that part of the variability in the optical proxy algorithms is related to differences in phytoplankton taxa and community composition, composition of non- phytoplankton particles, and ecosystem function (i.e., recycling community or not). 3. Can we build better proxies by taking these differences, as well as other environmental parameters that can be remotely sensed, into consideration? We are entering an era (or we are already there?) when most estimates of POC are derived using optical proxies (in-situ or remotely sensed). These estimates of POC have been and will continue to be used to derive carbon budgets and fluxes (i.e., primary productivity, ecosystem predictions, etc.), as well as impact public policy and decision- making. Hence, it is an imperative to improve POC optical proxy algorithms by evaluating all aspects of variability for POC and optical measurements, and by assessing uncertainties in the proxy-derived POC concentrations. We propose to: " Conduct an intensive field program (taking advantage of ship time and space provided by collaborators) that will allow us to collect data on hydrography, inherent optical properties (including polarized angular scattering), POC, suspended particulate matter (SPM), particle size distribution (PSD), HPLC pigments, and plankton size and carbon biomass from a dynamic range of ecosystem types. " Use best-practice POC and other biogeochemical parameter sampling and analysis protocols and use carefully calibrated (and inter-calibrated) optical instruments to constrain methodological sources of variability in both optical and POC measurements. " Use this extensive dataset to develop a multi-sensor, ecosystem-based remote sensing algorithm that will improve estimation of the oceanic POC pool, thereby allowing new insights into the dynamics of POC, as well as SPM and phytoplankton carbon biomass, in the surface ocean. " Evaluate the applicability of newly available remote sensing products such as Sea Surface Salinity (Aquarius/NASA) and polarized scattering measurements (Parasol/CNES, future PACE & ACE/NASA) to improve retrieval of POC, and reduce uncertainty in its estimation. We believe that the proposed research is timely and needed to support NASA OCEAN BIOLOGY AND BIOGEOCHEMISTRY's current programmatic goals that address "Science investigations to advance the development and utilization of new and/or multisensor remote sensing approaches to estimate important ocean biology and biogeochemistry (ecosystem and carbon cycle) properties".

Publications:

Babic, I., Mucko, M., Petric, I., Bosak, S., Mihanovic, H., Vilibic, I., Dupcic Radic, I., Cetinic, I., Balestra, C., Casotti, R., Ljubesic, Z. 2018. Multilayer approach for characterization of bacterial diversity in a marginal sea: From surface to seabed. Journal of Marine Systems. 184, 15-27. DOI: 10.1016/j.jmarsys.2018.04.002

Cetinic, I., Poulton, N., Slade, W. H. 2016. Characterizing the phytoplankton soup: pump and plumbing effects on the particle assemblage in underway optical seawater systems. Optics Express. 24(18), 20703. DOI: 10.1364/OE.24.020703

2015 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Characterizing the phytoplankton soup: Pump and plumbing effects on the particle assemblage in underway uncontaminated seawater systems   --   (Nicole J Poulton, Wayne Slade, Ivona Cetinic)   [abstract]

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile