Project Funding: 2010 - 2013

NRA: 2009 NASA: New Investigator Program   

Funded by NASA

Abstract:
The overarching purpose of the research proposed here is to improve quantifications of global ocean primary production (PP) through new observations, reanalysis of existing time-series data and assessment of the role of community composition and size distributions relative to PP models for the expanding, stratified and nutrient-poor seascape of the North Pacific Subtropical Gyre. The underlying rationale of our proposal assumes that community structure and hence size structure can be viewed as an integrator of environmental variables and hence be used to predict the very photo-physiological properties used to model PP from space. Our specific project objectives are as follows: 1. Assess potential relationships between PP parameterizations and community structure derived from discrete pigment analyses, absorption spectra and particle size distributions (PSD) using Hawaii Ocean Time-series (HOT) data. 2. Conduct complementary in situ size-fractionation experiments to investigate the relationship between size structure and PP in a series of cruises conducted each year of this project and generate basis vectors for discrete size fractions. 3. Building on historical data analysis (Obj. 1) and ancillary experiments to refine our understanding of the system (Obj. 2) we will incorporate physiological parameterizations derived from in situ measurements of PSD and hyperspectral absorption with results of discrete pigment-based analysis into existing models of PP. In order to achieve our stated research objectives we will leverage partner resources and utilize established analytical methods. The HOT program routinely collects a full complement of biological, chemical and hydrographic data. The bio-optics portion of this program (1998-2009) has collected surface irradiance, upwelling and downwelling radiance, multispectral absorbance and attenuation, particle size distributions (as of 9/2009) and fluorescence based assessments of primary productivity (FRRF, 2002-ongoing). Leveraging this program (see support letters from Church and Letelier), with the addition of a hyperspectral absorbance and attenuation meter (funds requested), will allow for a multi-scale assessment of community structure- productivity relationships. Measurements of euphotic zone PP (0-200m) parameterizations will be compiled from in situ 24-hr free floating 14C arrays and 14C response curves conducted by the HOT program (2) size-fractionated 14C P-E response curves conducted over the first three years of this project and (3) filter-pad and in situ ac-s based spectral absorption coefficients and relative to spectrally resolved radiance. Community structure will be approximated by three independent means: (1) HPLC-based size classes (2) deconvolution of filter-pad and in situ ac-s based spectral absorption and (3) particle size spectra determined by a LISST-100X. Principal component analyses will be employed to identify the factors (biological and environmental) which influence measurements of algal photophysiology and productivity. Multiple regression analysis and inversion approaches will be used to estimate the contributions of phytoplankton pigment size-classes or the dominant mode of the PSD relative to spectral absorption coefficients and the quantum efficiency of carbon fixation. These data will ultimately be used to construct depth-resolved models of PP. This proposal is directly relevant to the NASA-NIP focus on the global carbon cycle and ecosystems. Specifically, this work will address NASA strategic goals to "achieve progress in quantifying global marine productivity" and enhance scientific understanding of "the role of oceans in the climate system and in improving predictive capability." Knowing that outreach does not end with publication, this effort is intimately linked with a series of workshops, resource development and mentoring activities intended to educate and encourage the young scientists of tomorrow.

2011 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Primary Productivity as a Function of Absorption, Pigment Based Phytoplankton Diversity And Particle Size Distributions   --   (Angelicque White, Amanda Whitmire)   [abstract]