Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

Background
Particulate Organic Matter (POM) in the ocean consists of a variety of material such as live organisms, zooplankton carcasses, organic debris, zooplankton fecal pellets, transparent exopolymer particles, and minerals of both biogenic and terrestrial origin. The adhesive, coagulative nature of these particles leads to the formation of aggregates that become dense enough to sink towards the sea floor (McDonnell et al., 2011). It is well understood that the flux of marine particulate matter is a key process that links the surface with the deep ocean, and is a controlling factor in the distribution of many elements that form the building blocks of marine biota (Buesseler et al., 2007). These sinking particles are closely linked to the biological carbon pump (Ducklow et al., 2001), represent a key component in the ocean food web and can also act as a sink for inorganic minerals and pollutants that are scavenged by the sinking particles.

Sample collection
The BATS program uses a method developed by Knauer et al. (1979), which was used extensively at the VERTEX time-series site in the northeast Pacific, and is suitable for the assay of all levels of sinking flux found in the ocean. Particle flux is collected within a floating array of polycarbonate tubes (7 cm diameter by 53 cm height) containing a buffered brine solution with polycarbonate filters at the bottom. During monthly cruises to the BATS site, tubes are deployed at three depths (150, 200, and 300 meters) for a target time of 72 hours, depending on weather and conditions. The array is tracked using Argos, Iridium, RDF, and AIS localization units.

Before the array is deployed, tubes are arranged in deployment racks for the different depths and filled with a heavy brine (~85 ppt) and 2% formalin solution.  Equipment used and the specific arrangement of the array is represented in Figure 1 (See Supplemental Files section). Four tubes are deployed for carbon and nitrogen determinations, three tubes are deployed for phosphorus counts, and three tubes are prepared (but not deployed) for blank counts. 

Upon recovery, the ambient seawater above the interface (at approximately half height of the tubes) is siphoned off and the brine in the lower half of the tube is drained through the filter by means of opening a valve. Tubes are disassembled inside a fume hood and the pre-weighed polycarbonate filters containing the flux sample are transferred to clean petri dishes. Samples are misted with pH buffer solution once in the petri dish to keep them moist. Misting is done during transfer of samples as well as during the time they remain stored at 4ºC until analysis. Care is taken to store samples no longer than 3 to 6 months to prevent any biological processes that could modify organic carbon contents.

Sample analysis
After recovery, filters are examined under a microscope at 12x and 25x magnification to remove swimming zooplankton and other organisms which are not considered sediment flux. Manual removal is needed to prevent overestimation of sinking material that could skew the end results. The remaining flux on each filter is scraped into a bolus, dried and then placed into a silver capsule. For each depth, three samples are acidified to to remove inorganic carbon prior to measurement of organic carbon and nitrogen.  The non-acdified sample (fourth bolus) is measured for total carbon. Samples are analyzed with a CE440 Elemental Analyzer (Exeter Analytical), which combusts and reduces the sample, converting all C and N present into CO₂ and N₂. These gas concentrations are measured by thermal conductivity detectors and converted to electrical millivolt signals. Calibration coefficients are then used to convert millivolt outputs to carbon and nitrogen concentrations in micrograms. Acetanilide conditioners and machine blanks are also run to standardize the instrument and monitor performance and accuracy during a run. (See Data Processing Section below for additional information).

The PITS samples that are collected for determination of total particulate phosphorus (PPhos) are analyzed at Bigelow Laboratory of Ocean Sciences following the methods described in Lomas et al. (2010). The PPhos samples have swimmers removed (as detailed above) and are then analyzed using the ash-hydrolysis method of Solarzano and Sharp (1980).  This procedure does not separate inorganic from organic phosphorus and thus results should be considered as total particulate phosphorus.    

Considerations, concerns, and challenges
Sediment traps are the only tools for directly collecting sinking particles in the ocean. They are largely un-calibrated in the field and there are significant unresolved questions on their accuracy and precision. It is assumed that the collection of particles is linearly related to the aperture area of the sediment trap and that this collection is an accurate estimate of the mass of sinking particles at that depth and the particle sinking speeds. But hydrodynamics and other factors influence the collection of material by sediment traps so the interpretation of trap data should be approached with caution (Antia, 2005; Butman et al., 1986; Gardner et al., 1980; Kahler and Bauerfeind, 2001; Lee et al., 1988). The U.S. JGOFS Planning Report #10 provides an overview of these issues (U.S. JGOFS Planning Office, 1989) and there have been significant published papers on trap accuracy since that report.

• Any investigator using sediment traps should become aware of the facts and challenges in order to make informed decisions about appropriate methods for their investigation.
• Any scientist looking to use sediment trap data should be familiar with the factors affecting flux estimates, the methods used for the study, and the assumptions made for the flux calculations.

The CE440 elemental analyzer calculates the amount in micrograms (ug) of C and N present in a sample. However, results are reported in milligrams carbon per square meter per day (C mg/m2day). The raw data downloaded from the instrument provides K values, blank values, R and Z values (in milliVolts), and calculated C and N values (ug). 

For BATS processing, the mean of all the calculated K values is used for C and N estimations, and therefore a slightly different K is used than that of the CE440 software. The calculations for the K value for BATS are as follows:

          R - Z - B
K =    ------------
          C (or N)

where:
B (mV) = Blank capsule reading in millivolts (i.e the first run with ID ‘blank’)
R (mV) = Sample reading in mV from standards (Std1's)
Z (mV) = Instrument baseline, without capsule
C (ug) = mass of carbon. Acetanilide (ug) x 0.7109 from Std1’s
N (ug) = mass of nitrogen. Acetanilide (ug) x 0.1036 from Std1’s

Then, to calculate the Carbon or Nitrogen content in the sample, we use an average of the field blanks (FB) rather than the instrument blank measured using the following equation:
                                        R - Z- FB
Carbon content (ug)  =   -------------- 
                                              K

where FB = Average_R(mV) minus Average_Z(mV)

Since the elemental content measured is a part of the total sample captured (assuming some sample was lost in the scraping and bolus loading process), we adjust the carbon or nitrogen content to represent the entire filter sample:

                          C_CE440  
C_adjusted =   ----------------- * (M_sample*1000)
                           M_bolus

where:
C_adjusted (ug) = Carbon content adjusted to represent the entire filter sample
C_CE440 (ug) = Carbon in subsample calculated by CE440 mV data in MATLAB program.
M_bolus (ug) = subsample weight taken from microbalance when putting bolus in silver capsule
M_sample(ug) = average sample and filter weight minus average filter weight

Finally, the flux is calculated over the trap area, and number of deployment days, in milligrams (mg):

                  C_adjusted
C_flux =  ---------------------- *1000
                (0.0039m^2 * T)

where:
C_flux = mg/m2/day
0.0039m^2 = is the cross-section area of the trap with a 7cm diameter
T = number of days
*1000 = converts the ug to mg

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- converted latitude and longitude to decimal degrees
- added columns for Cruise_type and Cruise_num
- added column for ISO date
- missing data identifier of -999 maintained as per PI request

A full description of the BATS research program (including links to the processed BATS data) is available from the BATS Web site (see above for Project URL/ Project Website links). Any data contributed from selected ancillary projects are listed (linked) in the 'Datasets Collection' section below.  

Collaborative Research: The Bermuda Atlantic Time-series Study: Sustained Biogeochemical, Ecosystem and Ocean Change Observations and Linkages in the North Atlantic (Years 31-35)
Awards OCE-1756105, OCE-1756054, and OCE-1756312)
NSF award abstract
Long-term observations over several decades are a powerful tool for investigating ocean physics, biology, and chemistry, and the response of the oceans to environmental change. The Bermuda Atlantic Time-Series Study, known as BATS, has been running continuously since 1988. The research goals of the BATS program are: (1) to improve our understanding of the time-varying components of the ocean carbon cycle and the cycles of related nutrient elements such as nitrogen, phosphorus, and silicon; and, (2) to identify the relevant physical, chemical and ecosystem properties responsible for this variability. In addition, the BATS program has strong and diverse broader impacts, contributing to the field of ocean sciences by providing high quality ocean observations and data for seagoing scientists and modelers, and a framework through which researchers can conceive and test hypotheses. This award will support the operations of the BATS program for five more years.

The primary BATS research themes are as follows: (1) Quantify the role of ocean-atmosphere coupling and climate variability on air-sea exchange of CO2, and carbon export to the ocean interior; (2) Document trends and the controls on the interannual to decadal scale variability in carbon and nutrient cycles to their coupling in the surface and deep ocean via the Redfield Ratio paradigm; (3) Quantify the response of planktonic community structure and function, and impact on biogeochemical cycles to variability in surface fluxes and dynamical processes; (4) Facilitate development, calibration and validation of next generation oceanographic sensors, tools and technologies; and, (5) Generate a dataset that can be utilized by empiricists, modelers and students. This research integrates ocean physics, chemistry and biology into a framework for understanding oceanic processes and ocean change in the North Atlantic subtropical gyre. The existing 29 years of BATS data provide robust constraints on seasonal and interannual variability, the response of the Sargasso Sea ecosystem to natural climate variability, and signal detection of potential ocean changes. This project would extend the BATS program through years 31-35 to address a series of ten interlinked questions through integrated research approaches and a multitude of collaborative efforts. In addition to the themes above, and embedded into the ten questions and approaches, the BATS team will focus on, for example, coupling of particle production and biogeochemistry; revisiting the complexities of the biological carbon pump; oxygen decline; and changes in the hydrography, physics, ocean carbon cycle and biogeochemistry of the Sargasso Sea. The highest quality data observation and collection will be maintained and used to address these questions. Importantly, a wide range of collaborations at the BATS site, spanning the physical and biogeochemical disciplines, will aid these broad goals. Strong links to community stakeholders, and close collaboration (including methods intercomparisons and personnel exchanges) with the Hawaii Ocean Time-series are proposed. This work will extend the research findings of the project into educational and training opportunities within and beyond the oceanographic community, including training and mentorship of both undergraduate and graduate students.

Please see the BATS Web site (http://bats.bios.edu) for additional information.

List of References (PDF)

The Ocean Carbon and Biogeochemistry (OCB) program focuses on the ocean's role as a component of the global Earth system, bringing together research in geochemistry, ocean physics, and ecology that inform on and advance our understanding of ocean biogeochemistry. The overall program goals are to promote, plan, and coordinate collaborative, multidisciplinary research opportunities within the U.S. research community and with international partners. Important OCB-related activities currently include: the Ocean Carbon and Climate Change (OCCC) and the North American Carbon Program (NACP); U.S. contributions to IMBER, SOLAS, CARBOOCEAN; and numerous U.S. single-investigator and medium-size research projects funded by U.S. federal agencies including NASA, NOAA, and NSF.

The scientific mission of OCB is to study the evolving role of the ocean in the global carbon cycle, in the face of environmental variability and change through studies of marine biogeochemical cycles and associated ecosystems.

The overarching OCB science themes include improved understanding and prediction of: 1) oceanic uptake and release of atmospheric CO2 and other greenhouse gases and 2) environmental sensitivities of biogeochemical cycles, marine ecosystems, and interactions between the two.

The OCB Research Priorities (updated January 2012) include: ocean acidification; terrestrial/coastal carbon fluxes and exchanges; climate sensitivities of and change in ecosystem structure and associated impacts on biogeochemical cycles; mesopelagic ecological and biogeochemical interactions; benthic-pelagic feedbacks on biogeochemical cycles; ocean carbon uptake and storage; and expanding low-oxygen conditions in the coastal and open oceans.

The United States Joint Global Ocean Flux Study was a national component of international JGOFS and an integral part of global climate change research.

The U.S. launched the Joint Global Ocean Flux Study (JGOFS) in the late 1980s to study the ocean carbon cycle. An ambitious goal was set to understand the controls on the concentrations and fluxes of carbon and associated nutrients in the ocean. A new field of ocean biogeochemistry emerged with an emphasis on quality measurements of carbon system parameters and interdisciplinary field studies of the biological, chemical and physical process which control the ocean carbon cycle. As we studied ocean biogeochemistry, we learned that our simple views of carbon uptake and transport were severely limited, and a new "wave" of ocean science was born. U.S. JGOFS has been supported primarily by the U.S. National Science Foundation in collaboration with the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the Department of Energy and the Office of Naval Research. U.S. JGOFS, ended in 2005 with the conclusion of the Synthesis and Modeling Project (SMP).

Program description text taken from Chapter 1: Introduction from the Global Intercomparability in a Changing Ocean: An International Time-Series Methods Workshop report published following the workshop held November 28-30, 2012 at the Bermuda Institute of Ocean Sciences. The full report is available from the workshop Web site hosted by US OCB: http://www.whoi.edu/website/TS-workshop/home

Decades of research have demonstrated that the ocean varies across a range of time scales, with anthropogenic forcing contributing an added layer of complexity. In a growing effort to distinguish between natural and human-induced earth system variability, sustained ocean time-series measurements have taken on a renewed importance. Shipboard biogeochemical time-series represent one of the most valuable tools scientists have to characterize and quantify ocean carbon fluxes and biogeochemical processes and their links to changing climate (Karl, 2010; Chavez et al., 2011; Church et al., 2013). They provide the oceanographic community with the long, temporally resolved datasets needed to characterize ocean climate, biogeochemistry, and ecosystem change.

The temporal scale of shifts in marine ecosystem variations in response to climate change are on the order of several decades.  The long-term, consistent and comprehensive monitoring programs conducted by time-series sites are essential to understand large-scale atmosphere-ocean interactions that occur on interannual to decadal time scales.  Ocean time-series represent one of the most valuable tools scientists have to characterize and quantify ocean carbon fluxes and biogeochemical processes and their links to changing climate.

Launched in the late 1980s, the US JGOFS (Joint Global Ocean Flux Study; http://usjgofs.whoi.edu) research program initiated two time-series measurement programs at Hawaii and Bermuda (HOT and BATS, respectively) to measure key oceanographic measurements in oligotrophic waters. Begun in 1995 as part of the US JGOFS Synthesis and Modeling Project, the CARIACO Ocean Time-Series (formerly known as the CArbon Retention In A Colored Ocean) Program has studied the relationship between surface primary production, physical forcing variables like the wind, and the settling flux of particulate carbon in the Cariaco Basin.

The objective of these time-series effort is to provide well-sampled seasonal resolution of biogeochemical variability at a limited number of ocean observatories, provide support and background measurements for process-oriented research, as well as test and validate observations for biogeochemical models. Since their creation, the BATS, CARIACO and HOT time-series site data have been available for use by a large community of researchers.
 
Data from those three US funded, ship-based, time-series sites can be accessed at each site directly or by selecting the site name from the Projects section below.