Award: OCE-0927098

The Oceanic Flux Program (OFP) sediment trap time series, the longest running time series of its kind, has continuously measured particle fluxes in the deep Sargasso Sea since 1978. OFP results provided the first direct observation of seasonality in the deep ocean, and have documented the tight coupling between deep fluxes and upper ocean processes and the intensity of biological reprocessing of sinking flux in the ocean interior. The synergy among OFP and other research programs co-located at the Bermuda time-series site has provided unprecedented opportunities to study the linkages between ocean physics, biology and chemistry and particle flux generation and particle recycling in the ocean interior. The OFP time-series is beginning to reveal how the deep ocean is affected by large-scale climatic forcing, such as the North Atlantic Oscillation. Understanding the oceanic particle flux is important as this process regulates many aspects of ocean health and global element cycles. Excepting deep vent communities, the export flux of organic matter from the ocean's surface waters- including the particle flux and a smaller contribution from vertically migrating zooplankton - ultimately provides the food source for all life in the ocean interior. The overall fluxes and flux ratio of organic matter and carbonate shells produced by microscopic marine organisms control, in part, the oceanÆs ability to absorb excess carbon dioxide from the atmosphere. The depths at which nutrient and bioreactive elements that are incorporated into sinking organic debris are released as particles undergo degradation and dissolution, coined the "length scale of remineralization", affects the redistribution of nutrients by ocean currents which, in turn, regulates geographic patterns of ocean productivity. Particle flux also efficiently transfers suspended materials, such as continentally-derived clays advected by currents from ocean margins, to the deep ocean and eventually to the seafloor, as these materials are ingested by zooplankton during nonselective feeding and repackaged into larger sinking particles such as fecal pellets and aggregates. Additionally, particulate pollutants, deposited from the atmosphere or transported by ocean currents, are also transferred via the particle flux from surface waters to the deep ocean and eventually to the seafloor, where they contaminate deep ocean and benthic ecosystems. One of the central objectives of OFP research is to elucidate the processes that control particle flux generation and particle cycling within the ocean interior. This is not a straightforward task. The particle flux is an aggregate of materials from diverse sources: organic and mineral remains of microscopic phytoplankton and animals, fecal pellets and amorphous aggregates produced by zooplankton, repackaged clay particles sourced from continental margins, minerals formed in situ as particles degrade, and other materials scavenged from the surrounding seawater. Only rarely do sinking particles formed in surface waters survive the trip to the abyssal seafloor. Rather, as particles sink they are subjected to microbial remineralization, dissolution, consumption by deeper-dwelling zooplankton, particle dissaggregation and desorption/adsorption reactions. The result is a continuing evolution in particle flux concentration and composition from the surface to the ocean seafloor. While globally only a small fraction (<1% of surface production) survives its trip to the seafloor, this residual material retains a wealth of information about past ocean conditions which can be used to reconstruct the earthÆs history. Two overarching goals drive core OFP research activities. The first is to extend the time-series by collection of new flux samples that are of the highest possible sample quality and that have maximal oceanographic context. The second is to elucidate the causal processes that drive oceanic particle flux through comparative studies of flux m...