Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

All measurements used in the net oxygen production estimates from data collected at the San Pedro Ocean Time-series (SPOT) station (33 33'N, 118 24'W). Data are also published as Table 3 in the following publication:
Haskell, W. Z., et al. 2016. An organic carbon budget for coastal Southern California determined by estimates of vertical nutrient flux, net community production and export. Deep-Sea Research I, 116, 49-76. doi:10.1016/j.dsr.2016.07.003

See complete methodology in Haskell et al. (2016). In summary:
This study is part of an effort aimed at characterizing the biological response to upwelling at SPOT on 21 cruises between January 2013 and June 2014; the Upwelling Regime In-Situ Ecosystem Efficiency (Up.R.I.S.E.E.) study.

Dissolved oxygen/argon ratios: Samples for O2/Ar analysis were collected from Niskin bottles in 300 and 500 mL glass flasks equipped with airtight Louwers-Hapert valves (with 3 high-vacuum greased Viton O-rings in valve stem) and side arms. Prior to sampling, each bottle was poisoned with 150 uL saturated HgCl2, dried in an oven at 50 C, then evacuated to <1 mtorr and weighed. Samples were later sent to the laboratory of Rachel Stanley (WHOI) where they were analyzed for O2 (m/z = 32) and Ar (m/z = 40) by peak jumping using a Finnigan MAT 253 IRMS.

CTD oxygen sensor calibration: The CTD oxygen sensor (Seabird SBE 43) was calibrated using Winkler titrations on samples collected in duplicate at 5 depths on every CTD cast. Winkler titrations were performed the day after each cruise for most of the one day cruises, and typically two days following each two-day cruise, with equipment and procedure outlined by Langdon (2010). In one case (Up-1), Winkler analyses were performed 4 days after the cruise.

Oxygen mixed layer depths were determined as the depth at which the oxygen concentration was 0.5% different from the surface concentration (Castro-Morales and Kaiser, 2012) and ranged between 10 m and 35 m. Euphotic depths were typically between 35 m and 65 m, with the exception of Up-8 and Up-15 (30 m and 70 m). For 9 cruises (Up-13 to Up-21), the base of the euphotic zone was determined with the CTD as the depth at which 1% of the surface photosynthetically available radiation (PAR) is measured. Prior to Up-13, there was no PAR sensor on the CTD unit. Since the deep chlorophyll-a maximum (DCM; determined from CTD fluorescence profiles) is almost always above the euphotic depth in Southern California Bight (Cullen and Eppley, 1981), for the remainder of the cruises, the euphotic depth was defined as 10 m below the DCM. However, during Up-2, -3, and -4, the DCM was within the mixed layer. For these three cruises, the euphotic depth was defined as 15 m below the MLD.

BCO-DMO Processing:
-modified parameter names to conform with BCO-DMO naming conventions;
-formatted dates to yyyy-mm-dd;
-created separate columns for MLD and EuphD;
-added site name, lat, and lon from information on metadata form.

The marine biological pump is one of the primary pathways via which anthropogenic carbon dioxide may be sequestered from the atmosphere and exported to the deep ocean as organic carbon. While the link between nutrient supply and high primary productivity in upwelling regions is well established, factors controlling the organic carbon export efficiency of upwelling ecosystems are not well known. Scientists from the University of Southern California and Pomona College plan to determine the factors that control the rates and magnitudes of two components of biological production, Net Community Production (NCP) and Gross Primary Production (GPP), as well as particulate organic carbon export efficiency, at the San Pedro Ocean Time Series, a coastal site in the California Borderland during periods of minimal and high upwelling velocity over a 2-year span. At this site, past and ongoing observations of hydrography and carbon rain will provide an historical context for interpreting results and mechanisms at work.

Rates of NCP and GPP will be quantified at different upwelling intensity, using dissolved oxygen to argon (O2/Ar) ratios and the oxygen triple isotope composition of dissolved oxygen (O2). The export of organic carbon will be established using 234Th (thorium) profiles in the water column, coupled with floating sediment trap deployments, and the development of a carbon isotope balance for the water column. Upwelling will be characterized using non-steady state budgets for atmospheric 7Be (beryllium) input and its depth-integrated decay, as well as estimating rates based on remote measurements of wind stress curl and budgets for dissolved inorganic carbon and silicon. Application of the O2/Ar ratio and the oxygen triple isotope approach will require depth-integrated profiles of these tracers to evaluate the impact of upwelling on mixed layer inputs and use of non-steady state models during seasonal transitions in upwelling. The comprehensive data set to be obtained should provide insights into the organic carbon export efficiency under variable upwelling regimes and help to relate the satellite-based measurements of chlorophyll to the organic carbon export of these highly productive ecosystems.

Broader Impacts: One graduate and one undergraduate student from the University of Southern California and two undergraduate students from Pomona College would be supported and trained as part of this project.