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www.biogeosciences-discuss.net/6/27/2009/
doi:10.5194/bgd-6-27-2009
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Short term variability of dissolved lipid classes during summer to autumn transition in the Ligurian sea (NW Mediterranean)
1CNRS-INSU UMR 6117, Laboratoire de Microbiologie, Géochimie et Ecologie Marines, Observatoire du Centre d'Océanologie de Marseille, Campus de Luminy, 13288 Marseille Cedex 09, France
2CNRS, UMR 7621, Laboratoire d'Océanographie Biologique de Banyuls, Avenue Fontaulé, BP44, 66650 Banyuls sur mer, France
3UPMC, Univ. Paris 06, UMR 7621, Laboratoire ARAGO, Avenue Fontaulé, BP 44, 66650 Banyuls sur mer, France
4Observatoire Océanologique de Villefranche-sur-mer; Université Pierre et Marie Curie-Paris 6; Institut National des Sciences de l’Univers (INSU), CNRS(UMR 7093), BP28, 06234 Villefranche sur mer, France
Abstract. Changes in concentration and composition of dissolved lipid classes (Iatroscan TLC/FID) were examined at daily to month scale, in relation to the hydrological and biological situation at a central site of the Ligurian sea, NW Mediterranean during the PECHE-DYNAPROC 2 experiment (14 September to 17 October). Dissolved lipid concentrations (TLd) and lipid to DOC ratios varied in the range 5.3–48.5 μ g l−1 and 0.01 to 0.08 respectively, along the 0–1000 m water column. The highest TLd concentration values were found in the 0–150 m surface layer coinciding with phytoplankton biomass. Lipid class composition provided valuable information on the origin of DOM, and the changes that occurred during the period investigated. The significant correlations (p<0.01, n=87) between glycolipids from chloroplast membrane (MGDG) (38.7±8.5% of TLd, n=166), and various phytoplankton pigments (chlorophyll cs-170, violaxanthin, diadinoxanthin, zeaxanthin, and lutein), suggested that picoeucaryotes were the major source of dissolved lipids. Lipid metabolites (37.6±11.1%, n=166), the second most important compounds in TLd, showed a greater degree of degradation of lipids in this transition period than previously observed earlier in the year. A contribution of lipids to DOM in the mesopelagic zone was observed before the winter mixing: At mid time of the cruise (4–6 October), zooplankton wax esters biomarkers (WE, 5.5–13.6 μg L−1) appeared in the 0–150 m surface layer. WE were observed later and deeper in the mesopelagic layer (6 to 11 October), accompanied by re-increases of hydrocarbons (6–8 October) and phospholipids concentrations (12 October) in the 400–1000 m depth layer. Zooplankton migration and/or fecal pellets egestion, followed by DOM release from POM, were likely responsible for the appearance of these lipid signatures in the mesopelagic layer, which occurred during the period of low wind (<15 knots) (28 September–12 October). The low salinity water lenses that appeared twice during the cruise in the 40–80 m surface layer had little effect on total biogenic lipid concentrations. Lower concentrations in phosphoglycerides and hydrocarbons than the nearby sea water suggested different microbial assemblages and different level of HC contamination in this less-salted water.
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Citation: Goutx, M., Guigue, C., Aritio, D., Ghiglione, J., Pujo-Pay, M., and Andersen, V.: Short term variability of dissolved lipid classes during summer to autumn transition in the Ligurian sea (NW Mediterranean), Biogeosciences Discuss., 6, 27-69, doi:10.5194/bgd-6-27-2009, 2009. Bibtex EndNote Reference Manager XML
