Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information

As part of the VERTIGO project, Multiple Unit Large Volume in-situ Filtration System (MULVFS) sampling took place during two week-long intensive study periods at ALOHA (in 2004) and K2 (in 2005). This dataset includes data from K2.

Final review by the data submitter was not received after it was imported into the BCO-DMO data system. Data have been published "as is".

Associated Publication:
Bishop, J.K.B.and Wood, T.J. (2008) Particulate Matter Chemistry and Dynamics in the Twilight Zone at VERTIGO ALOHA and K2 Sites. Deep-Sea Research I 55, 1684-1706. doi: 10.1016/j.dsr.2008.07.012

As part of the VERTIGO project, Multiple Unit Large Volume in-situ Filtration System (MULVFS) sampling took place during two week-long intensive study periods at ALOHA (in 2004) and K2 (in 2005). This dataset includes data from K2.

MULVFS was first described in Bishop et al., 1985. MULVFS consists of 12 ship-electricity powered pump units deployed simultaneously to kilometer depths using a dedicated (unified) 1000 m long electromechanical cable and winch system. MULVFS sample depths were 10, 35, 60, 85, 135, 185, 235, 310, 460, 560, 660, 760, and 810 m at K2. The shallowest sample was always within the surface mixed layer. VERTIGO casts were timed to capture particles near local noon and midnight to investigate the effects of diurnal zooplankton migrations on particle distributions. At K2, 2 day/night pairs were obtained.

Each pump unit can collect samples of particulate and dissolved species using three flow paths. Check and gas release (de bubbler) valves protect filter samples from the effects of back flow, contamination, and disruption due to trapped air on deployment and degassed air expansion on recovery. The later is a problem in shallow samples.

Depending on depth and particle concentration, 2000–16 000 L volumes of seawater are filtered under a suction of ~0.8 atmospheres over 4–5 h through the main multi-stage (3 anti-washout baffles and two filter stages) filter holder. The first anti-washout baffle is a heavy polyethylene plastic cover with incised 1 cm scale triangular flaps centered over each of the 52 tubes of the second baffle stage and was added to ensure particle retention under strong current shears.

The main filter series (with an effective filtration diameter of 24.5 cm) consists of a 51 um polyester weave mesh prefilter supported by 149 um polyester mesh and 1.2 cm spaced 1.2 cm thick plastic grid in the prefilter stage, followed by two identical Whatman QMA quartz fiber filters supported by 149 um polyester mesh and 149 um porous polyethylene frit. All filters and components are acid cleaned. The three particle size fractions represented by prefilter and QMA filters are >51, 1–51, and <1 um. Fiber flters are 'depth' filters and particles are captured from the flow by the fibers, not pores. Thus a second filter captures additional small particles that pass through the first (Bishop and Edmond, 1976). The "<1 um" fraction, thus represents some of particles in the larger submicron particle class (Bishop et al., 1977, 1985).

The second flow path, with 500–2000 L water flow capacity was used for separate multi-stage filter assemblies and in-line Mn radionuclide adsorption cartridges (Charette et al., 1999). Refer to the Supplemental Document "VERTIGO MULVFS Methods" for the filter assembly used by T. Trull (University of Tasmania, UTAS) The third ('side arm') flow path was used for simultaneous attachment of up to six 47 mm filter holders or smaller absorbers. We used two for separate quantification of >0.4 um Si and for >0.4 um Ba and Mn (Poretics Polycarbonate, 0.4 um, Osmonics, Inc.). About 30% of the time all side arm filter holders had a common 0.4 um filter and the volume was apportioned by number of samples collected. When different filters/adsorbers were used we estimated flow through each type apportioned by flows measured under suction aboard ship.

Blank samples (filters mounted on a non-operating pump and lowered to depth for the cast duration) were processed identically to all other samples.

Aboard ship, MULVFS samples were photographed under controlled lighting using a NIKON COOLPIX 5700 digital camera (Lam and Bishop, 2007) and processed in depth order within 2 hours of the end of cast. All work was performed in a class 100 laminar- flow bench; non-contaminating gloves, sub sampling templates, scalpels, and tweezers were used. QMA filters were sub sampled for up to six other investigators using sharpened acid leached ~45 mm diameter acrylic tubes; "pie slice" sub samples equivalent to 1/8 to 1/4 of each >51 um sample were cut using a stainless steel scalpel. When rare, larger zooplankton and small fish were removed from the MULVFS prefilter samples prior to sub sampling. The remaining sample was lightly "misted" with 15 mL of 18.2 MOhm Milli-Q water under weak suction (<10 cm Hg) to reduce salt loading, oven dried at 60°C for 1-2 days, and then stored flat in trace metal certified polyethylene bags.

The "Side Arm" 0.4 um filter samples were misted under mild vacuum with ~1.5 mL of Milli-Q water, and then transferred directly to acid leached 125 mL polyethylene bottles in which they were later analyzed. This eliminates fractionation of major sea salt components (e.g., Na from Ca).

Sample processing at Lawrence Berkeley National Laboratory (LBNL) was performed in a class-100 laminar flow fume hood in a class-10000 laboratory environment and followed Bishop et al., (1977, 1985). For analysis by Inductively Coupled Plasma Mass Spectrometer (ICP-MS), ~1/50th of each QMA filter was sub sampled following Bishop et al. (1985) and ~1/40th of each 51 um prefilter was cut using a stainless steel scalpel (guided by eye to avoid zooplankton) using a rectangular acrylic template with recessed center. Sub samples were transferred to separate 125 mL acid leached - dried Nalgene® polyethylene bottles, flooded with 10 mL of 0.6 N ultra pure HCl (Seastar Chemicals Baseline Acid), and heated at 60°C overnight (~16 hours). Each leach solution was filtered (0.4 um) and then diluted with 18.2 MOhm Milli-Q water to 50 grams weight. Solutions were further diluted (1:4) with Milli-Q water and treated with an indium spike (final In conc ~0.7 ppb) and then analyzed using a Finnigan Element II ICP-MS. Mixed element standards, and CASS III seawater, were prepared at multiple dilutions in the same 0.12 N HCl matrix. Elements determined were Li*, Na, Mg*, Al, P, K*, Ca*, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr*, Y, Cd, I, Cs, Ba, Tl, Pb, Bi, Ce, Nd, U*. Elements marked with asterisks (*) were corrected for sea salt components using Na (Bishop et al., 1977).

Groups from Woods Hole Oceanographic Institution (WHOI) and University of Tasmania (UTAS) were provided fresh filter sub samples for 234Th, C and N, and for Corg, N, δ13Corg, and δ15N, respectively. The >51 um material was rinsed from the polyester "pie slices" using 0.8 um filtered seawater onto 25 mm diameter 0.4 um silver filters, dried at 50 °C, and analyzed as described by Trull et al. (2008). A drying oven mishap resulted in loss of many of the QMA Corg samples from Cast M03 at ALOHA. The 234Th samples were air-dried after/during counting aboard ship and stored frozen in Petri dishes for later analysis for C and N at WHOI. QMA in-situ sample blanks (~3 mg C per 25.4 cm diameter filter) were applied to the data. The use of in-situ blanks compensates for adsorption of dissolved species onto filters during filtration (Turnewitsch et al., 2007).

WHOI Corg and N data for QMA samples from cast M07 and M08 were low by factors of two to three compared with UTAS results. The M08 sub samples analyzed at WHOI had sat wet for considerable time before CN analysis (John Andrews, notes) and the same problem must have impacted their M07 sub samples. Similar problems may have affected some ALOHA samples from Cast M04, which also were not oven dried. We report all data but use the WHOI Corg QMA data for ALOHA (M1, M2, M4, M5) and the UTAS (combined <1 and 1-51 um results) QMA Corg and N data for K2; The <1 um WHOI results were retained for casts M07, 09, and 10 for comparison purposes. All >51 um Corg samples at K2 and ALOHA were UTAS processed.

Notes from dataset file header:
# Bishop CN calcs as of April 29 2007 results nearly final.
# QMA blanks 25.4 cm diameter filter - all dipped blanks (averaged except for cast 8).
# Trull Filter data as calculated by Buesseler.
# Nitrogen results: many dipped MULVFS sample blanks below detection. The results shown here are an upper limit of N.

# Note nearest surface samples in >51 um size fraction from casts 8 and 10 at night are contaminated with significant numbers of copepods (see Bishop and Wood (2008)).
# treat cast 7 and 8 lt1 and 1-51 PC and PN with caution.
# gt0.4 Corresponds to analysis of a side-arm filter.
# gt51, 1-51, lt1 designations correspond to filtration order as water passes through a 51 um prefilter and paired QMA filters. A single QMA filter quantitatively captures particles >1.2 um; a pair of QMA filters traps particles to 0.8 um size.
# lt51 - sum of paired QMA filter data.
# samples identified by T_ were samples from a separate filter holder.

Quality Flag Definitions:
0 = sample is ok.
1 = possibility of over estimate of flow 10-20%.
2 = samples were wet when stored CN anomlously high C and N anomalously low.
3 = samples may be mixed up.
4 = main MULVFS flow volume adjusted based on consistency with other analyses.
5 = CN anomalously low.
6 = sample not run.

BCO-DMO Processing history:
Version 1:
2008-07-07 - contributed by Jim Bishop.
2008-11-12 - Cruise_ID added manually; date, event, ev_code, lon, lat from cruise logs merged with original data.
2008-11-12 - added to OCB database; Steve Gegg, BCO DMO.

Version 2:
2020-12-01 - processed revised data contributed by Jim Bishop in November 2020; made the following edits:
- added locations and dates from separate locations file;
- renamed fields to conform with BCO-DMO naming conventions;
- removed duplicate columns;
- replaced missing data values with 'nd' ('no data').

NSF Award Abstract:
In this study, researchers at the Woods Hole Oceanographic Institution, Virginia Institute of Marine Science, University of California - Santa Cruz, University of California - Santa Barbara, University of Tasmania, and NIWA-Australia will work collaboratively to answer a difficult question in marine biogeochemistry: What controls the efficiency of particle transport between the surface and deep ocean? More specifically, what is the fate of sinking particles leaving the upper ocean and what factors influence remineralization length scales for different sinking particle classes? Knowing the efficiency of particle transport is important for an accurate assessment of the ocean carbon sink. Globally, the magnitude and efficiency of the biological pump will in part modulate levels of atmospheric carbon dioxide.

The research team intends to test two basic hypotheses about remineralization control, namely: (1) particle source characteristics are the dominant control on the efficiency of particle transport; and/or that (2) mid-water processing, either by zooplankton or bacteria, controls transport efficiency. To do so, they will conduct process studies at sea focused on particle flux and composition changes in the upper 500-1000m of the ocean. The basic approach is to examine changes in particle composition and flux with depth within a given source region using a combination of approaches, many of which are new to the field. These include neutrally buoyant sediment traps, particle pumps, settling columns and respiration chambers, along with the development of new biological and geochemical tools for an integrated biogeochemical assessment of the biological pump. Two sites will be studied extensively on three-week process study cruises: the Hawaii Ocean Time-series site (HOT) and a new moored time-series site in the subarctic NW Pacific (Japanese site K2; 47oN 160oE). There are strong contrasts between these sites in rates of production, export, particle composition and expected remineralization length scales.

Evidence for variability in the flux vs. depth relationship of sinking particles is not in dispute, but the controls on particle transport efficiency through the twilight zone remain poorly understood. A lack of reliable flux and particle characterization data within the twilight zone has hampered our ability to make progress in this area, and no single approach is likely to resolve these issues. The proposed study will apply quantitative modeling to determine the net effects of the individual particle processes on the effective transport of carbon and other elements and to place the shipboard observations in the context of spatial and temporal variations in these processes

Besides the obvious contributions to the study of the oceanic and planetary carbon cycles, there are broader outcomes and impacts forthcoming from this project. Graduate and undergraduate students will be included in all aspects of the research, and the involvement of non-US PIs will encourage exchange of students and post-docs between labs in different countries. In addition, the component groups will continue to maintain science web sites designed for both public and scientific exchange where the broader and specific goals and outcomes of this work can be communicated.

Original PI-provided project description:
The main goal of VERTIGO is the investigation of the mechanisms that control the efficiency of particle transport through the mesopelagic portion of the water column.

Question: What controls the efficiency of particle transport between the surface and deep ocean? More specifically, what is the fate of sinking particles leaving the upper ocean and what factors influence remineralization length scales for different sinking particle classes? VERTIGO researchers have set out to test two basic hypotheses regarding remineralization control, namely:
1. particle source characteristics are the dominant control on the efficiency of particle transport; and/or that
2. mid-water processing, either by zooplankton or bacteria, controls transport efficiency.

To test their hypotheses, they will conduct process studies in the field focused on particle flux and composition changes in the upper 500-1000m of the ocean. The basic approach is to examine changes in particle composition and flux with depth within a given source region using a combination of approaches, many of which are new to the field. These include neutrally buoyant sediment traps, particle pumps, settling columns and respiration chambers, along with the development of new biological and geochemical tools for an integrated biogeochemical assessment of the biological pump. Three week process study cruises have been planned at two sites - the Hawaii Ocean Time-series site (HOT) and a new moored time-series site in the subarctic NW Pacific (Japanese site K2; 47oN 160oE) - where there are strong contrasts in rates of production, export, particle composition and expected remineralization length scales.

Evidence for variability in the flux vs. depth relationship of sinking particles is not in dispute but the controls on particle transport efficiency through the twilight zone remain poorly understood. A lack of reliable flux and particle characterization data within the twilight zone has hampered our ability to make progress in this area, and no single approach is likely to resolve these issues. The proposed study will apply quantitative modeling to determine the net effects of the individual particle processes on the effective transport of carbon and other elements, and to place the shipboard observations in the context of spatial and temporal variations in these processes. For rapid progress in this area, we have organized this effort as a group proposal taking advantage of expertise in the US and international community.

The efficiency of particle transport is important for an accurate assessment of the ocean C sink. Globally, the magnitude and efficiency of the biological pump will in part modulate levels of atmospheric CO2. We maintain that to understand present day ocean C sequestration and to evaluate potential strategies for enhancing sequestration, we need to assess possible changes in the efficiency of particle transport due to climate variability or via purposeful manipulations of C uptake, such as via iron fertilization.

VERTIGO Acknowledgments: (from K.O. Buesseler, et al / Deep-Sea Research II 55 (2008) 1522-1539) We thank the officers, crew and shore-based support teams for the R/V Kilo Moana (2004) and R/V Roger Revelle (2005). Funding for VERTIGO was provided primarily by research grants from the US National Science Foundation Programs in Chemical and Biological Oceanography (KOB, CHL, MWS, DKS, DAS). Additional US and non-US grants included: US Department of Energy, Office of Science, Biological and Environmental Research Program (JKBB); the Gordon and Betty Moore Foundation (DMK); the Australian Cooperative Research Centre program and Australian Antarctic Division (TWT); Chinese NSFC and MOST programs (NZJ); Research Foundation Flanders and Vrije Universiteit Brussel (FD, ME); JAMSTEC (MCH); New Zealand Public Good Science Foundation (PWB); and internal WHOI sources and a contribution from the John Aure and Cathryn Ann Hansen Buesseler Foundation (KOB). A number of individuals at sea and on shore, helped make the VERTIGO project a success, including: J. Andrews, C. Bertrand, R. Bidigare III, S. Bray, K. Casciotti, M. Charette, R. Condon, J. Cope, E. Fields, M. Gall, M. Gonneea, P. Henderson, T. Kobari, D. Kunz, S. Saitoh, S. Manganini, C. Moy, S. Okamoto, S. Pike, L. Robertson, D. Ruddick and Y. Zhang. Suggestions by three anonymous reviewers and help by the editor, R. Lampitt, are also greatly appreciated.

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.