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TZEX - Project Website
Carbon Flux through the Twilight Zone- New Tools to Measure Change

Project Summary
This project sets out to develop improved particle flux collectors and use these to answer key science questions associated with C fluxes and exchange via sinking particles at the Bermuda Atlantic Time-series Study (BATS) site. Currently at BATS, we can’t balance surface ocean C budgets, annual new production estimates, or link production and community structure to predict particle export, and regularly fail to capture episodic flux events. At the same time, we are trying to answer these questions using an imperfect tool, the drifting sediment trap, a device that has served us well but has not changed significantly since the early 1980s.

This program is both innovative and ambitious, with the development and engineering of new tools and its emphasis on the collection of multi-annual time-series data, while being realistic in starting from proven technology. We start by building upon our recent success with the neutrally buoyant sediment trap (NBST), but recognize that continuous flux collection and swimmer free samples are needed, as envisioned for our new design- the Twilight Zone EXplorer (TZEX).

Sampling Protocols
A selection of PI sampling protocols and preliminary shared data are posted here.

TZEX NBST Sampling Protocol

AE0809 Sept. 2009 Cruise Summary Data and Event/CTD Logs

WHOI 11/29/09 Image of the Day- Sunset on the RV Atlantic Explorer.

Ocean color and altimeter data sets for TZEX study region (D. Siegel/E. Fields)

Dehairs, F., A. de Brauwere, M. Elskens, U. Bathmann, S. Becquevort, S. Blain, P. Boyd, K. Buesseler, E. Buitenhaus, M. Gehlen, G. Herndl, C. Klass, R. Lampitt, D. Lefevre, U. Passow, H. Plous, F. Primeau, L. Stemmann and T. Trull (2008). Controls on Organic Carbon Export and Twilight Zone Remineralization: An Overview of the EUROCEANS Workshop . Oceanography, 21(3): 92-95.

Dehairs, F., A. de Brauwere and M. Elskens (2008). Organic Carbon in the Ocean's Twilight Zone. EOS, Transactions American Geophysical Union, 89 (38): doi:10.1029/2008EO380004.

The biological pump and processes regulating the flux of particles in the ocean. Carbon dioxide fixed during photosynthesis by phytoplankton in the upper ocean can be transferred below the surface mixed layer via three major processes: i) passive sinking of particles, ii) physical mixing of particulate and dissolved organic matter (DOM), and iii) active transport by zooplankton vertical migration. The sinking flux includes senescent phytoplankton, zooplankton fecal pellets, molts and mucous feeding-webs (e.g., larvacean houses) and aggregates of these materials. The sinking particle flux decreases with depth as aggregates are fragmented into smaller, non-sinking particles, decomposed by bacteria, and consumed and respired by zooplankton. This remineralization returns carbon and nutrients to dissolved forms. The structure of the planktonic community affects the composition and the sinking rates of particles. Particle size, form, density, and the content of biogenic minerals affect sinking and remineralization rates.

The Proposal
Here's a link to our NSF Carbon and Water proposal entitled "Carbon Flux through the Twilight Zone- New Tools to Measure Change". Note that funding was cut significantly, so the project is now a 4 (vs. 5) year effort and the "Stage 4" one week process cruises have been cut.

The Principal Investigators
Woods Hole Oceanographic Institution
Ken O. Buesseler (
Carl H. Lamborg (
James R. Valdes (

Bermuda Institute of Ocean Sciences
Michael W. Lomas (

University of California, Santa Barbara
David A. Siegel (

Virginia Institute of Marine Science
Deborah K. Steinberg (

The Study Site
Bermuda Atlantic Time-series Study

The Funding Programs
NSF Ocean Sciences
Carbon and Water in the Earth System

New Information
Please submit all information/corrections/improvements to the site to Mary Zawoysky at

Updated: November 30, 2009

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