Table of Contents

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

DOP Utilization (ATP3, DOP) CTD data
Biogeochemical data collected on transect cruises studying
Dissolved Organic Phosphorus throughout the western Sargasso Sea.
Data are from several cruises over the span 2006 to 2008.

Note the cruise identifiers for the Atlantic Explorer were originally formatted as XYY## (e.g. X0806 was the 6th cruise in 2008).  The data files include cruise IDs of this type.  The vessel operator changed the cruise ID syntax several years after the cruise and the official cruise ID syntax was changed to AEYY##.  For example, AE0810 should be the same cruise as X0810.  One exception for this dataset is that X0804 is cruise ID AE0810.

Related files and references:
Detailed information on analyses:
Lomas, M.W., Burke, A., Lomas, D.A., Bell, D.W., Shen, C., Ammerman, J.W., Dyhrman, S.T. 2010.
Sargasso Sea phosphorus biogeochemistry: An important role for dissolved organic phosphorus (DOP).
Biogeosciences 7: 695-710.

Other published work:
Michelou, V.K., Lomas, M.W., Kirchman, D.L. Phosphate and ATP uptake by cyanobacteria and heterotrophic
bacteria in the Sargasso Sea. Limnology and Oceanography, in press.

McLaughlin, K., Sohm, J.A., Cutter, G.A., Lomas, M.W., Paytan, A. 2010. Phosphate cycling in the Sargasso Sea:
Investigation using the oxygen isotopic composition of phosphate, enzyme labeled fluorescence, and turnover times.
Journal of Geophysical Research - Biogeosciences, in press.

Longnecker, K., Lomas, M.W., and Van Mooy, B.A.S. 2010. Characterizing the abundance and diversity of
heterotrophic bacterial cells assimilating phosphate in the sub-tropical North Atlantic Ocean.
Environmental Microbiology, in press.

Orchard, E.D., Ammerman, J.W., Lomas, M.W., Dyhrman, S.T. 2010. Dissolved inorganic and organic phosphorus
uptake in Trichodesmium and the microbial community: The importance of phosphorus ester in the Sargasso Sea.
Limnology and Oceanography, 55:1390-1399.

Casey, J., Lomas, M.W., Michelou, V., Orchard, E.D., Dyhrman, S.T., Ammerman, J.W., and Sylvan, J. 2009.
Phytoplankton taxon-specific orthophosphate (Pi) and ATP uptake in the northwestern Atlantic subtropical gyre.
Aquatic Microbial Ecology, 58:31-44.

Van Mooy, B.A.S., Fredricks, H.F., Pedler, B.F., Dyhrman, S.T., Karl, D.M., Koblizek, M., Lomas, M.W., Moore,
L.R., Moutin, T., Rappé, M.S., and Webb, E.A. 2009. Phytoplankton in the oligotrophic ocean use non-phosphorus
lipids in response to phosphorus scarcity.
Nature Geosciences, doi:10.1038/nature07659.

Sampling and Analytical Methodology:
Detailed methods for all data collected as part of this study can be found in the publications
arising from this study (references given below). This contains information on analytical
machines and certified standards where applicable.

Sample QA/QC procedures followed those of the Bermuda Atlantic Time-series Study (BATS).
At the point of collection, any leaking niskin bottles were noted on the master cast sheets
and samples were taken from a different niskin fired at the same depth as the leaking bottle.
No data are reported for leaking Niskin bottles. During sample analysis standard curves
and/or certified standards were carefully examined to ensure that they were consistent with
expectations and accurate. If nothing was found, then we examined other data from that
niskin to see if other samples are in question. If no obvious error or problem was found,
the data were considered OK and in the range of environmental data that this study hoped
to observe.

Sample accuracy and precision:
Sample accuracy was assessed by using certified standards, for those measurements where
standards are available (dissolved oxygen, nutrients, salinity). Certified standards were
run with each analytical run and compared to long term control charts for respective analyses.
Samples were not run until certified standards were shown to be accurate for that analytical
run. Sample precision was determined by analyzing replicate samples (not replicate analyses
on the same sample) and therefore is higher than analytical precision due to the inclusion
of sampling error. At the concentrations observed during this study, sample precision was
<5% for stock measurements and <10% for rate measurements. Some analyses, namely dissolved

oxygen and salinity, were much better and often had a sample precisions <1%. These precision

estimates are consistent with the long term QA/QC seen with the BATS program.

The provided data files are complete matrices and therefore not every sample (columns) will be
taken from every Niskin fired (rows). Data that were either not collected, or were associated
with leaking Niskins, or were found to be in error for other reasons are denoted by "nd" in the
spreadsheets.

Data Processing:
Most of the data given in this dataset are not derived variables and are calculated using
reasonably standard equations as given in the appropriate reference above. The one exception
is CTD data. Raw CTD data were processed using SBE-Data Processing software using configuration
and calibration files provided by the Shipboard Science technician. Sensors were calibrated
every 6 months. Manual determinations of dissolved oxygen, salinity and HPLC Chlorophyll a,
once passing the above QA/QC steps, were taken as correct. CTD sensor data was regressed against
the appropriate manual variable. In all cases, regression statistics were very strong and linear.
CTD data were corrected to manual measurements using the regression data and it is this corrected
data that is given in the associated data files.

Only nutrient analyses were close to analytical method detection limits (MDL). MDLs were estimated
as 3x the standard deviation of the lowest standard used for the analysis and are ~30nM for nitrate
and phosphate using a standard autoanalyzer. We used the MAGIC co-precipitation method for phosphate
which lowered our MDL to ~1.5nM. Samples below the MDL are reported as calculated for the reason
that they are somewhere between the MDL and a true zero; we consider listing them as either to be
incorrect.

BCO-DMO Edits
- Parameter names modified to conform to BCO-DMO convention
- date reformatted to YYYYMMDD
- time reformatted to HHMM
- lat/lon padded to 7 decimal places
- added CruiseId column and combined all CTD data into one dataset
- X0606 station 7 year corrected from 2007 to 2006
- Lat/Lons for X0606 standardized to positions from BGC data

Photosynthetic uptake of CO2 by oceanic phytoplankton and the export of the resulting organic carbon to the deep sea comprise a 'biological pump' capable of extracting globally significant amounts of CO2 from the atmosphere. Mounting evidence suggests that primary production in two of the larger subtropical ocean gyres, the Western Tropical/Subtropical Atlantic and the North Pacific Subtropical Gyre (NPSG), may be controlled by the availability of inorganic phosphorus. This conclusion is based on vanishingly low inorganic phosphorus (SRP) concentrations, sub-nanomolar in some locales, ratios of inorganic nutrient availability that greatly exceed the canonical Redfield Ratio, and high rates of dissolved organic phosphorus (DOP) hydrolysis.

Indeed, data collected in the Sargasso Sea shows a 30% decline in DOP inventories during summer stratification. Moreover, several studies have documented significant taxonomic variability in the ability to hydrolyze and to assimilate phosphorus from organic sources We hypothesize that despite rapid turnover times, chronically low and seasonally invariant SRP concentrations at BATS cannot support measured rates of primary production without utilization of additional P from the DOP pool. Moreover, we hypothesize that inherent physiological differences among microbial taxa represents a significant source of temporal and spatial variability in DOP utilization rates that is yet neither understood nor constrained.

Our specific research objectives are:
1. To quantify temporal and spatial variability in DOP hydrolysis in the Sargasso Sea with measures of whole-community and taxon-specific alkaline phosphatase
2. To quantify temporal and spatial variability in taxon-specific SRP and DOP uptake rates by combining flow cytometry and radioisotope methodologies.
3. To quantify whole-community total P uptake rates through BAP (biologically available phosphorus) assays, as well as SRP and model compound DOP uptake and regeneration rates.
4. To identify factors regulating rates of DOP hydrolysis and assimilation using experimental nutrient manipulations, and to evaluate the role of DOP in supporting primary production in the Sargasso Sea.

To successfully meet our objectives, we propose to employ three cruise sampling strategies: CORE, PROCESS, and CRUISES OF OPPORTUNITY. The CORE cruises and CRUISES OF OPPORTUNITY will be conducted in conjunction with the BATS biogeochemical time-series program. The PROCESS cruises are principal-use cruises that are designed to allow a more intensive study on the mechanisms of and controls on DOP hydrolysis and utilization in the Sargasso Sea.

An understanding of ocean ecosystem function is important on a broad scale. This project will provide information critical for successful modeling efforts constrain predictions of the strength of the oceanic biological pump, as well as provide information of interest to students, teachers and the general public. If in fact DOP supports a significant, and previously unquantified, fraction of the annual primary production in the Sargasso Sea, then diversity in biological metabolic processes in the central oceans plays a greater role in the global carbon cycle - including regulation of atmospheric CO2 - than we recognize at present. The overall goal of the student teaching/training programs at BBSR, WHOI and Rutgers is to expose students to oceanographic research, its global significance, and its impact on their daily lives. As such, we will incorporate data on DOP cycling in the Sargasso Sea into a problem-based learning module for courses taught by the PIs and submit our curriculum to the appropriate digital repository (e.g. www.dlese.org). The PIs have a strong commitment to direct mentoring, and they will also sponsor a minimum of three undergraduate researchers each year in their laboratories, and support the research and training of MIT/WHOI Joint Program and Rutgers University graduate students.