Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence-although each with important uncertainties-lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.
The GEOTRACES Intermediate Data Product 2014 (IDP2014) is the first publicly available data product of the international GEOTRACES programme, and contains data measured and quality controlled before the end of 2013. It consists of two parts: (1) a compilation of digital data for more than 200 trace elements and isotopes (TEls) as well as classical hydrographic parameters, and (2) the eGEOTRACES Electronic Atlas providing a strongly inter-linked on-line atlas including more than 300 section plots and 90 animated 3D scenes. The IDP2014 covers the Atlantic, Arctic, and Indian oceans, exhibiting highest data density in the Atlantic. The TEI data in the IDP2014 are quality controlled by careful assessment of intercalibration results and multi-laboratory data comparisons at cross-over stations. The digital data are provided in several formats, including ASCII spreadsheet, Excel spreadsheet, netCDF, and Ocean Data View collection. In addition to the actual data values the IDP2014 also contains data quality flags and 1-sigma data error values where available. Quality flags and error values are useful for data filtering. Metadata about data originators, analytical methods and original publications related to the data are linked to the data in an easily accessible way. The eGEOTRACES Electronic Atlas is the visual representation of the IDP2014 data providing section plots and a new kind of animated 3D scenes. The basin-wide 3D scenes allow for viewing of data from many cruises at the same time, thereby providing quick overviews of large-scale tracer distributions. In addition, the 3D scenes provide geographical and bathymetric context that is crucial for the interpretation and assessment of observed tracer plumes, as well as for making inferences about controlling processes. (C) 2015 The Authors. Published by Elsevier B.V
ABSTRACT-Sedimentation rates were determined daily over a 2 wk period (late April -early May 1992) under post spring bloom conditions at a permanent station in the Bjernafjorden, Norway. Samples collected using floating sediment traps deployed at 50 and 100 m depth showed that sedimented seston, particulate organic matter, carbonate and lithogenic + opal fractions were, on average, twice as high at 100 m (221, 99, 51 and 76 mg m-2 d ', respectively) as at 50 m (119, 62. 27 and 34 mg m-2 d ' l , respectively). Faecal pellets made up the bulk of sedimenting matter, accounting for 87 and 92% of the average total organic carbon recorded at 50 and 100 m, respectively. The remaining sedimented matter consisted mainly of tintinnids. Diatoms cells and resting spores, coccolithophorids and flagellates contributed a minor fraction. It is postulated that the vertical flux of faecal pellets was determined by a combination of 3 factors: (1) relatively high standing stock of actively grazing mesozooplankton dominated by calanoid copepods and appendicularians, which are known for t h e~r high faeces production rates; (2) a relatively high abundance of the cyclopoid copepod Oithona s~rnllls, which is reported to feed on faecal pellets produced by calanoid copepods, suggesting that coprophagy in the water column was high; (3) a phytoplankton community dominated by diatoms and coccollthophorids, whose mineral skeletons accelerate sinking rates of faecal pellets.
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