Table of Contents

• Coverage
• Dataset Description
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Program Information
• Funding

CTD data at the locations where bottles were tripped.

Carbon Flux Through the Twilight Zone - New Tools to Measure Change

Building upon the success of the VERTIGO project, we continue to work to improve our understanding of how materials travel from the surface to the deep ocean. This pathway is called the "Biological Pump" which refers to the combined activities that lead to a quick pathway for plant and animal debris (molts, fecal pellets, loose aggregated material) to sink as marine "snow" or a particle into the deep ocean. In the open ocean, this cycle is largely a biological one, though in some settings, transport of material delivered by dust may matter (e.g. TENATSO - Cape Verde time series project).

The "twilight zone" is a region of low light below the ocean's sunlit surface "euphotic" zone, and above the deep ocean boundary (around 1000m or 3000 feet). It is in this mysterious layer where most of the sinking particles of the world's ocean are consumed by the animals that live at depth.

In a new project starting in late 2006, we are designing an autonomous vehicle called the "Twilight Zone EXplorer" (TZEX) to sample the ocean particle flux and make remote measurements in the twilight zone. Beginning in 2007, we will be starting to sample on a monthly basis at Bermuda, as part of the BATS (Bermuda Atlantic Time-Series) program using our existing particle flux collectors, the Neutrally Buoyant Sediment trap.

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.

Funding

The TZEX project is funded as part of the NSF Carbon and Water in the Earth System crosscutting solicitation aimed at closing significant gaps in our understanding of the complex relationships between and within the global water and carbon cycles.

NSF link: http://www.nsf.gov/funding/pgm_summ.jsp?pims_id=13651&org=OCE

References:

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 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.