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

Following the first several years of the BATS project it was deemed necessary by the JGOFS steering committee and BATS PI's to conduct validation cruises in the vicinity of the nominal BATS site to better understand the mesoscale and larger scale variability of the region. In particular, a focus of the BVAL cruises was to assess the spatial scale representation of the BATS and Hydrostation ‘S’ programs. Initial focus of the BVAL cruises was to investigate mesoscale variability and meridional gradients of the local region. Later, cruises focused on specific mesoscale eddies (e.g., McGillicuddy et al., 1998; McGillicuddy et al., 1999) and effects of tropical cyclones through the local region. In the year 2000 it was deemed more important to document the larger scale changes in the North Atlantic Subtropical gyre so BVAL cruises established a transect line from ~ 35N to 19N (Bermuda to Puerto Rico) very similar to the WOCE A22 repeat hydrography line (Johnson et al., 2020). These annual Bermuda to Puerto Rico transects have been run since 2000 and target stations at every one degree of latitude and typically have been conducted in September/October of each year to capture maximal heat content in the upper ocean. However, since this timeframe coincides with high tropical cyclone activity the cruises were reluctantly (as of 2022) moved to begin in June/July of each year for safety and operational reasons. In the pentad prior to 2022 every BVAL cruise was significantly impacted by multiple tropical cyclones. Additionally, some BVAL cruises are transects from the US east coast to Bermuda and are opportunistic cruises leveraging times when the BIOS resident vessel (R/V Weatherbird II or R/V Atlantic Explorer) is in transit for other research cruises or ship yard visits. Parameters presented are the same as provided in the standard BATS datasets. 

Methods and Sampling

Phytoplankton use pigments to absorb energy from the sun to drive photosynthesis. Chlorophyll-a is used as the primary light harvesting molecule while other accessory pigments (chlorophyll-b, chlorophyll-c, and carotenoids) assist by expanding the light absorption capability of the organism, therefore increasing efficiency and adaptability (Bidigare et al., 2002).

Many individual algal pigments or combinations and ratios are taxon-specific. Therefore, pigment composition from seawater samples can be used to separate major algal groups and result in chemotaxonomic characterization. These analyses can be used to determine phytoplankton community structure and physiological state of the autotrophic assemblage (Wallerstein et al., 1999; Bidigare et al., 2002) 

The methodology described here is based on the Protocols for the Joint Global Ocean Flux Study (JGOFS) Core Measurements (BATS, 1997), and describes the use of high performance liquid chromatography (HPLC) for the rapid separation of phytoplankton pigments with detection limits for chlorophylls and carotenoids on the order of one nanogram (Bidigare, 1991). This HPLC method was adopted as BATS protocol in July 1994 (BATS 70 cruise). This method uses less solvent and gives improved peak separation and better resolution at lower concentrations.

Field sampling
Discrete samples are collected monthly using Niskin bottles at the Bermuda Atlantic Time-series Study site from depths ranging from the surface to 250 meters. Expeditious sampling and contamination prevention protocols were used to obtain the best possible samples, since the physico-chemical and biological parameters of the Niskin water become increasingly altered with time spent on deck, especially if in full sunlight. Sea water is filtered using glass fiber filters (GF/F) with standard pore size of 0.7 microns and the filtered samples then flash frozen and stored at -80ºC until analysis. 

HPLC pigment measurements
Water samples were analyzed for the concentration of various phytoplankton pigments following the method of Wright et al. (1991) as modified by Dr. Robert Bidigare. Pigments present in a seawater sample can be separated by high-performance liquid chromatography (HPLC) based on differences in polarity.  Pigment polarities determine how the pigments interact with the solid phase (column) and the mobile phase (solvent) within the HPLC. Pigments that are less polar will be more attracted to the non-polar stationary phase and take longer to pass through than more polar pigments, thus a temporal separation is achieved. The length of time it takes for the pigment to elute is known as the retention time. Under comparable conditions, pigment retention times are consistent and can therefore be used for identification when compared to a reference. The retention times are determined using a diode array detector (DAD), which detects absorption across a range of wavelengths in the UV-Vis portion of the spectrum. The separated pigments are transported by the flowing mobile phase to the detector, where the solution passes through a flow cell and is dispersed by a diffraction grating. Photodiode arrays detect the light intensity for each wavelength, which is converted to an electrical signal, resulting in a visible peak on a chromatogram. Concentration is proportional to the area of the peak, and can be calculated using calibration factors determined from known standards (aka response factor), in addition to other parameters such as volume of water sampled and dilution factors.

The HPLC currently in use is an Agilent 1100 series. The results from two different wavelengths are reported in this method, 436nm and 450nm. All pigments except divinyl chlorophyll-a produce a signal at 436nm. However, divinyl and monovinyl chl-a cannot be separated at 436nm due to a similar detector response, so 450nm is also used to try and separate mono and divnyl chl-a since divnyl absorbs at this wavelength and monovinyl does not.

Fluorometric measurements
In addition to the HPLC measurements, pigment samples from BATS are also analyzed using fluorometric techniques. Fluorescence is the physical property of compounds to absorb light energy and instantaneously re-emit light at a different wavelength to the absorbed light. Fluorescent compounds, such as chlorophyll-a, have characteristic absorption and emission wavelengths. In fluorometry, a sample is excited at the appropriate absorption wavelength and the intensity of the emitted light is measured using a photodiode detector to give a raw fluorescence recorded value that is proportional to concentration. When compared to reference standards, the raw fluorescence measurements are used to calculate the concentration of the fluorescent material in the sample.

Prior to January 2020, fluorometry was performed on the Turner 10-AU fluorometer, whereas samples are currently analyzed using the Trilogy Fluorometer at BIOS. Data from the fluorometer is compared to the chlorophyll-a data from the HPLC which allows an extra quality control method to ensure data from both methods are similar. This data is being released as part of the BATS dataset since fluorometry is often used instead of HPLC in the oceanographic community for chlorophyll analysis.

Additional information
Additional details on methods, standardization, and calibration can be found in the BATS methods document (Protocols for the Bermuda Atlantic Time-series Study Core Measurements).

BATS HPLC Data Processing

Once a sample has been analysed, the peaks in the resulting chromatogram are manually integrated, as the automatic integration processing in the software (Agilent OpenLab Chemstation Version 2) is not suitable for the high number of analytes.

The manual integration tool within the software is used to draw a line along the baseline from the start to the end of the peak, from which the area of the peak can be determined. The peaks are identified and labelled using the saved retention times from calibration with known standards.

The signal from the HPLC is proportional to the concentration of the pigment in the sample and is used to calculate the final concentration (C) in ng/L of pigment using the following equation:

C = ( A * RF ) / V_inj * DF *  V_ext / V_f * 10⁶

where,

DF =  ( V_vial + V_ace + V_H20 ) / V_vial

A = HPLC Peak Area
RF = HPLC Response factor (determined during calibration)
V_inj = Injection volume on HPLC (normally 200µl)
V_{ext =} Extraction volume of filter (normally 3.2ml)
V_{f =} volume of water filtered during sample collection (normally 4000ml)
V_vial = volume of sample decanted into HPLC vial (normally 1000µl)
V_{ace =} volume of acetone added to HPLC vial (usually zero)
V_H20 = volume of water added to HPLC vial (usually 300µl)
10⁶ = volume conversion factor

Notes:

• Extraction volume is 3.2ml due to the 3ml of acetone added and the 0.2ml of seawater retained on the filter

An in-house Matlab (Version 2015b) processing script is used to extract the data required for the concentration calculation from various sources, including sample ID files, HPLC chromatogram reports, and fluorescence results reports. It then calculates the concentration of each pigment for each sample in ng/L.

Finally, the reported data are converted to ng/kg simply by multiplying by 1000 and dividing by the density of the sample which is calculated using either the bottle salinity or CTD salinity at time of sample collection and an assumed laboratory temperature of 24°C.

- imported "bval_pigments_v004.txt", and "bval_pigments_qcmask_v004.txt" into BCO-DMO system
- joined "bval_pigments_qcmask_v004.txt" and "bval_pigments_v004.txt" to add flag columns for the parameters
- converted longitude values to decimal degrees (degrees West are negative)
- converted date to yyyy-mm-dd format
- added Cruise_type, Cruise_num, Cast, Cast_type, and Bottle_number columns (extracted from ID column)
- added vessel names as defined in "bval_pigments_v004.txt"
- added cast types as defined in "bval_pigments_v004.txt"
- modified parameter names to conform with BCO-DMO naming conventions and to be more consistent with other BATS data submissions

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.