Sponsored by: National Aeronautic Space Administration & US J.G.O.F.S.
Project Period: March 15, 1998 – March 14, 2001
Principle Investigator: Paul G. Falkowski
Co-Principle Investigator: Michael J. Behrenfeld
Co-Principle Investigator: Zbigniew S. Kolber

The primary goal of this project is to improve ocean carbon models by describing how physical and chemical forcing affects the statistical distribution of key functional phytoplankton groups. This information is critical in predicting how changes in ocean physics and chemistry will influence total and new production in future ocean model scenarios. The research is coordinated with the Ocean Carbon-cycle Modeling Intercomparison Project (OCMIP), an international project initiated in 1995 by the Global Analysis, Interpretation and Modeling (GAIM) Task Force of the International Geosphere-Biosphere Program (IGBP).
The project focuses on the development of algorithms that predict how ocean physics and chemistry affect the spatial distribution of:

• trichodesmium sp.,the major nitrogen fixing organisms;
• diatoms, the major group responsible for export production;
• coccolithophores, which, as a consequence of calcification, raise pCO₂; and
• the polytaxonomic group of picoplankton, which, while they are the major carbon fixers, contribute little to carbon export.

The statistical distribution of these four functional groups will be analyzed using remotely sensed information in conjunction with sea truth data, and, based on the statistics of their distributions, “functional group profiles” will be generated. The “functional group profiles” give a probability of encountering each of the four groups in each grid cell of an OGCM. Based on these profiles, we can specify physical and chemical criteria that maximize and minimize the distributions of each group, and hence prospectively infer their distributions in climate change scenarios. From knowledge of the distributions of each group, the forcing and feedback between ocean circulation, chemistry and biological processes can be represented much more realistically in ocean general circulation/biogeochemical models.

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Sponsored by NSF – Division of Ocean Sciences
Principle Investigator: Paul G. Falkowski

This component of the Southern Ocean iron enrichment experiment is designed to provide the instrumentation and expertise for biophysical assessment of the factors limiting phytoplankton photosynthesis in the open waters of the Antarctic Ocean. Our techniques incorporate both real-time, continuous underway measurements, as well as discrete sample analysis and include: fast repetition rate (FRR) fluorometry, single-celled fast repetition rate (SCFRR) fluorometry, and low temperature fluorescence excitation/emission spectroscopy. These “tools” are capable of sensitively and reliably detecting and quantifying intrinsic biophysical limitations of phytoplankton photosynthetic processes, and provide diagnostic profiles for specific limiting factors such as iron. This program element (1) provides key data that directly tests the iron limitation hypothesis for high nutrient, low chlorophyll waters in the Southern Ocean, (2) quantifies the temporal and spatial photosynthetic responses to the iron enrichment, (3) provides the capability for real-time adaptive sampling within an enrichment area, and (4) helps to determine the taxonomic components that are iron limited, and to understand their responses to enrichment.

We propose to evaluate all of the basic variable fluorescence characteristics at sea. We will also perform post-cruise measurements.

Sponsored by: Office of Naval Research (ONR)

Principle Investigator:  Paul G. Falkowski

Co- Principle Investigators:  Zbigniew S. Kolber, Maxim Gorbunov

The major theme of this research project is to understand processes that contribute to fluorescence emission from benthic targets in the coastal and shallow waters with the overarching goal of developing parameterization schemes that optically detect anthropogenic objects. This effort is part of the larger Coastal Benthic Optics Program (CoBOP) DRI.

The research effort has three basic tasks:

1. To analyze data obtained from in situ fluorescence detectors, especially the scuba-based Fast Repetition Rate Fluorometer and to iteratively improve the instrumentation and retrieval algorithms in support of CoBOP field measurements.
2. To measure fluorescence lifetimes in the subnanosecond time domain from model organisms. This task, which will be carried out both in the field and at Rutgers University, will provide the fundamental knowledge for the interpretation of in situ lifetime measurements.
3. To determine the molecules that give rise to the specific fluorescence signatures and to characterize their spatial and temporal distributions in relation to variations in fluorescence yields. This latter task will address the first order applicability of CoBOP optical models to subtropical and tropical shallow water benthic environments.

Principal  Investigators:

Paul Falkowski	Rutgers University	falko@imcs.rutgers.edu
Michael Follows	M.I.T.	mick@plume.mit.edu
Yuan Gao	Montclair State University	gaoy@montclair.edu
Yoram Kaufman	NASA	kaufman@climate.gsfc.nasa.gov
Daniel Sigman	Princeton University	sigman@princeton.edu

Sponsored by: US Dept of Energy, Division of Basic Energy Bioscience
Project Period: March 1, 1999 – February 28, 2002
Principle Investigator: Paul G. Falkowski

This project addresses the basic molecular mechanisms responsible for the acclimation of the photosynthetic apparatus to changes in irradiance. We have recently identified that the redox status of the plastoquinone pool is a sensor that affects nuclear gene transcription in a eucaryotic green alga, Dunaliella tertiolecta (Escoubas et al., Proc. Nat, Acad. Sci. 92:10237-41). The research builds on that discovery by analyzing the signal transduction cascade and the cue/response functions.

The effect of redox modulation in the photosynthetic electron transport chain on the expression of a variety of nuclear genes is under investigation. The research goals are to characterize the key DNA binding factors, follow the effects of redox control on the activation of the binding factors, and examine how redox poise is related to environmental cues such as irradiance, temperature and CO2.

The research has broad implication for understanding how environmental information is transduced to biochemical information with photosynthetic organisms, and how that information, in turn, affects nuclear gene expression.