Tracking the Temporal and Spatial Variability of Dissolved Organic Matter, its Diagnetic State and Bioavailability During Various Bloom States in the North Atlantic

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National Science Foundation
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Ecology and Evolution

Overview–The North Atlantic phytoplankton bloom is among the most conspicuous biological events annually recorded ({McClain, 1990 #2967;Siegel, 2002 #1647;Yoder, 1993 #2966}.  This bloom represents a “hot spot” of biological activity during which a significant fraction of net community production (NCP) can be partitioned into the dissolved organic matter (DOM) phase {Duursma, 1963 #533; Williams, 1995 #1971}.  Recent work examining the spatial (horizontal and vertical) gradients of DOM in the north Atlantic coupled to measurements of mixing or water mass ventilation rates has estimated that as much as 81 Tg C as DOM is vertically exported out of the surface 100 m each year {Amon, 2003 #40; Carlson, 2010 #274}.  DOM export in the North Atlantic can contribute to as much as 20 % of export production; thus, representing an important contributor to the biological pump.  However, missing from these data sets is the valuable temporal resolution necessary to investigate the mechanisms that control DOM production, accumulation, and change in DOM quality as a result of changing bloom state and phytoplankton phenology.


Intellectual Merit– This project will leverages a large, recently funded,  NASA field-program entitled  “North Atlantic Aerosols and Marine Ecosystem Study (NAAMES)” (M. Behrenfeld Lead PI) designed to evaluate the fundamental controls of the north Atlantic phytoplankton bloom initiation, its magnitude and interannual variability. These objectives will be accomplished by coupling continuous water column and surface layer ecosystem properties from autonomous in situ sensors (Bio-Argo floats) and satellite observations with four 26-day coordinated ship and airborne field campaigns.  The NAAMES field work will collected physical, biological and biogeochemical data over varying physiological bloom states and associated phytoplankton phenology.  This funded field program and associated assets provide a unique opportunity to properly evaluate DOM dynamics and the associated change in the diagenetic state.  The main elements of this proposed work are:

-       Resolve meridional variability in DOC and 40°N to 57°N over four varying physiological states of a North Atlantic Spring Phytoplankton bloom.

-       Use temporal and spatial DOM profiles combined with MLD estimates from Ship based and ARGO floats to constrain the vertical DOM export resulting from convective overturn along the meridional transects.

-       Characterize a portion of the hydrolysable carbohydrate pool (i.e. dissolved combined neutral sugars; DCNS) to assess the variability in the diagenenetic state of Bloom produced DOM during varying physiological phases

-       Conduct DOM remineralization bioassay experiments to assess the bioavailability of Bloom produced DOM and the magnitude of surface produced DOM that resists or escapes microbial remineralization and persists (DOM Export potential).


Broader Impacts– The Galway Statement on Atlantic Ocean Cooperation is an international agreement that encourages the development of a large multidisciplinary research program focused on the coupled North Atlantic-Arctic system.  The work proposed here will contribute to that mission and help to provide a mechanistic understanding of carbon cycling in the context of the North Atlantic phytoplankton Bloom.   Data will be disseminated through established channels (i.e., BCO-DMO) and the results presented in peer-reviewed literature and at national and international conferences. Funds are requested to support the training of a graduate student.  In addition to traditional graduate training  this grant will also serve as a mechanism of mentoring for undergraduates. UCSB is officially recognized as a Hispanic-Serving institution and Carlson will continue to recruit Hispanic students into his research program. Carlson is committed to training the next generation of ocean scientists through public outreach lectures both on campus and in local  Jr. High and elementary schools.  Carlson and his graduate student also  mentoring high school students with science projects