Pulsed export of carbon in the north-western Mediterranean Sea  

作　　者：Michel DENIS Dominique LEFEVRE Melilotus THYSSEN Ian RJENKINSON Gérald GRÉGORI 

机构地区：[1]Aix Marseille Université,Universitéde Toulon,CNRS/INSU,IRD,Institut Méditerranéen d'Océanologie(MIO),Marseille cedex09 13288,France [2]Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China [3]Agency for Consultation and Research in Oceanography,Lavergne,19320 La Roche Canillac,France

出　　处：《Journal of Oceanology and Limnology》2023年第1期189-202,共14页海洋湖沼学报（英文）

基　　金：Supported by the PROOF Grant provided by the INSU-CNRS and was part of the PECHE project“Production and exportation of carbon:control by heterotrophic organisms at small time scales”。

摘　　要：The short term(hourly scale)variability of heterotrophic prokaryote(HP)vertical distribution and respiratory activity,was investigated in the north-western(NW)Mediterranean Sea.HP vertical distribution was determined on board by flow cytometry analysis of seawater samples collected by series of CTD casts.Cell counts and viability were determined for all samples.HP respiratory rates were determined later in the laboratory from filtered seawater samples(23 dm^(3))from 300-1150-m depth.The average cell viability was 94.8%±2.2%(n=240).There was no accumulation of dead cells,due to quick decay of damaged cells.In the epipelagic layer,three HP groups were distinguished,two(HNA1,HNA2)who se cells exhibited a high nucleic acid content and one(LNA)with low nucleic acid content cells.HNA2 was most populated at 50 m but not detected at 90 m and below,presumably aerobic anoxygenic photoheterotrophic bacteria(AAPs).The variability in HP abundance was mainly confined in the upper 80 m.A few secondary peaks of HP abundance were observed(80-150 m)in connection with abundance troughs in the surface layer.HP cells were continuously present in a wide layer around 500 m(mean 191×10^(3)cells/cm^(3)).Below this layer,HP abundance randomly exhibited peaks,coupled to respiratory rate peaks.The HP abundance and variability in the water column was suppressed during a strong wind event.The observed sporadic variability was tentatively interpreted through a pulsed carbon-export mechanism induced by the microorganism production of dissolved poly saccharide s,followed by flocculation and rapid sinking.This mechanism would thus contribute to(ⅰ)preventing organic matter accumulation in the epipelagic layer,(ⅱ)seeding the water column with live HP cells,and(ⅲ)supplying the aphotic water column with fre sh and labile organic matter.This important vertical flux mechanism needs further observations and modelling.

关 键 词：north-western Mediterranean Sea heterotrophic prokaryote(HP) cell viability cell respiration transparent exopolymeric particle(TEP) aggregation flow cytometry 

分 类 号：P731[天文地球—海洋科学]