Composition and degradation of marine particles with different settling velocities in the northwestern Mediterranean Sea

Abstract

Settling particles were collected from the Ligurian Sea in the northwestern Mediterranean Sea in May 2003 and separated by elutriation into different settling velocity classes (.230, 115-230, 58-115, and ,58 m d 21 ). Particles of the different classes were incubated for 5 d to study their biodegradability. Particulate opal content and organic compound composition (amino acids, pigments, lipids, and carbohydrates) were analyzed initially and at regular time intervals during the incubation period. Most particles (48-67% of total mass) sank at greater than 230 m d 21 and were dominated by large diatom-derived aggregates produced during the spring bloom period. The initial organic composition and the biological lability of these particles varied with settling velocity. The strong phytoplankton signal was visible in all settling velocity classes, while slower settling particles carried with them a greater zooplankton and bacterial signature. As the different class particles decomposed, their compositions changed and became more similar with time, with a dominance of compounds that suggests a more degraded state: the amino acids c-aminobutyric acid and b-alanine, the pigments pyropheophorbide and pheophytin, the deoxysugars fucose and rhamnose, and lipid metabolites (diglycerides and monoglycerides, alcohols, and free fatty acids). Biogenic opal in the particles dissolved faster in more degraded particles than in fresher particles, suggesting that loss of organic matter may expose opal to dissolution. The coupling of settling velocity and decomposition rate measurements shows quantitatively that slower settling particles are quickly degraded and AcknowledgmentsThis research was part of the MedFlux and PECHE (Production and Export of Carbon: Control by Heterotrophs at small temporal scale) programs and was supported by the U.S. National Science Foundation Chemical Oceanography Program (OCE-0136370, OCE-0136318, and OCE-0113687) and the French CNRS (Centre National de la Recherche Scientifique), respectively. Participation of B.M. was funded by ORFOIS (Origin and Fate of Biogetic Particle Fluxes in the ocean) (EVK2-CT2001-00100). We thank Michael Peterson, Lynn Abramson, Jenni Szlosek, Meaghan Askea, and Isabell Putnam for shipboard and laboratory help; David Hirschberg and Michael Peterson for CHN analysis; Claude Mante for help with statistical data treatment; and the captain and crew of the RV Seward Johnson II. We wish to acknowledge the associate editor and two anonymous reviewers for very helpful comments and suggestions on the manuscript. This is MedFlux contribution 7 and MSRC contribution 1318.

Role of slowly settling particles in the ocean carbon cycle

“…[22] Other studies [Goutx et al, 2007;Wakeham et al, 2009] reached the same conclusion after analyzing the composition of particles collected at 200 m in the Mediterranean Sea and separated by settling velocity. Samples from the Pacific Ocean also showed that material collected by in situ filtration, assumed to be suspended or with low settling rates, contained a remarkable abundance of labile organic compounds [Lee et al, 2000;Sheridan et al, 2002].…”

Data compilation of fluxes of sedimenting material from sediment traps in the Atlantic Ocean

“…The data include observations from a range of named sediment-trap designs: moored automatic Kiel sediment traps (Bauerfeind et al, 2009;Bauerfeind and Nöthig, 2011), cone-shaped SMT 230 Kiel and Mark VI/V traps (Wefer and Fischer, 1993), cone-shaped multi-sampling SMT 230 KMU traps (Romero et al, 2002;Fahl and Nöthig, 2007), conical particle interceptor traps (Antia et al, 1999), conical sediment McLane Mark-7 traps (Hwang et al, 2009), drifting Technicap PPS 5 sediment traps (Goutx et al, 2000), Kiel HDW traps (Jonkers et al, 2010), large-aperture timeseries Kiel-type traps Iversen et al, 2010), Mark-VII automated sediment trap (CARI-ACO), McLane Mark 78G-21 (Jonkers et al, 2010), multisample moored conical traps (Bory et al, 2001), Parflux Mark 7G-13 time-series sediment trap (Honjo and Manganini, 1993;Jickells, 2003a, b, c, d;Lampitt et al, 2001Lampitt et al, , 2010, Aquatec Kiel-type sediment trap (Neuer et al, 1997(Neuer et al, , 2007, indented rotary sphere (IRS) settling velocity and time-series mode sediment traps (Peterson et al, 2005;Goutx et al, 2007;Lee et al, 2009a, b), SMT 234 Aquatec Meerestechnik Kiel trap (Helmke et al, 2005), surface-tethered particle interceptor traps (BATS), and PPS-5 traps (Jonkers et al, 2010). Information is sometimes insufficient to ascertain whether two models are identical.…”

Regional and temporal variability of sinking organic matter in the subtropical northeast Atlantic Ocean: a biomarker diagnosis

“…Principal Components Analysis (PCA) is commonly used in the analysis of complex organic datasets (Goñi et al, 2000;Ingalls et al, 2006;Goutx et al, 2007). It is a multivariate regression analysis that reduces a large number of variables to a few principal components.…”