Spatio-temporal variation of suspended and sedimentary organic matter quality in the Bay of Marseilles (NW Mediterranean) assessed by biochemical and isotopic analyses.

Isotopic and biochemical features of suspended particulate organic matter (POM) in the water column and of sedimentary organic matter (SOM) were investigated seasonally in the Bay of Marseilles. Biochemical compounds (carbohydrates, lipids and proteins) were consistently more concentrated in POM than in SOM, with SOM mainly composed of insoluble carbohydrates. POM displayed lower δ(13)C and higher δ(15)N values than SOM.

C(25) highly branched isoprenoid alkenes from the marine benthic diatom Pleurosigma strigosum.

The hydrocarbon composition of the marine diatom Pleurosigma strigosum isolated from coastal Mediterranean sediments is described. A suite of five C(25) highly branched isoprenoid (HBI) alkenes with 2-5 double bonds were detected together with n-C(21:4) and n-C(21:5) alkenes and squalene. The analysis by (1)H and (13)C NMR spectroscopy of two isolated HBI alkenes allowed the structural identification of a novel C(25) HBI triene (2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadeca-5E,13-diene) and the first identification in diatom cells of 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)-pentadec-5E-ene, an HBI previously detected in marine sediments and particulate matter.