Fig 1.
Picture and scheme (with dimensions in mm) of an experimental tank (minicosm).
Table 1.
Comparison between (1) in situ unfiltered (noted ‘in situ’), (2) filtered seawater sampled inside the minicosms before the acidification step (noted “C1”) and (3) filtered seawater sampled inside the minicosms after acidification (noted “C2”).
Table 2.
Abiotic carbon export following an artificial dust deposition.
Table 3.
Mass budget in sediments traps and determination of lithogenic fluxes.
Fig 2.
Abundance ([TEP] in # mL-1) and volume concentration of transparent exopolymer particles (Cv in ppm) along the course of the three CHIPIE experiments in the two minicosms (non-acidified and acidified).
“C1” and “C2” refer to samplings performed before and after acidification, respectively. The filled area represents the range of TEP abundance and volume concentration based on the results in the minicosm non-acidified (black circles) and acidified (empty triangle). The x-axis (in log-scale) represents the number of hours after the artificial dust deposition at the surface of both minicosms represented as a vertical dashed line. Error bars correspond to standard deviations estimated considering a conservative counting error of 20%.
Fig 3.
Evolution of the spectral slope (δ) of the size distribution of transparent exopolymer particles (TEP; left panels) and the average diameter of TEP (right panels) in both minicosms after seeding for all CHIPIE experiments.
When δ decreases, the relative proportion (in number) of small particles increases. Circles and triangles represent data from the non-acidified and acidified minicosm, respectively.
Fig 4.
Microscopic image (x 200) of transparent exopolymer particles (TEP) stained with alcian blue.
In seawater collected in the Bay of Villefranche (unfiltered) on May 21st 2013 (A), after filtration “C1” (B) and “C2” (C), 1 hour after dust deposition (D) and at the completion of this CHIPIE 1 experiment (six days after dust addition; E).
Fig 5.
Relationship between the integrated lithogenic flux (mg m-2 d-1) and the particulate organic carbon (POC) flux (mg m-2 d-1) associated to the lithogenic ballasting (POClitho) over 6 days of each experiment.
Based on the results of the present study (black circles), a correlation equation was established with a slope of 0.012 (pvalue < 0.001, r2 = 0.985). Stars represent data from DUNE experiments R1 and R2 [15,46].