Degradation and Preservation of Organic Matter in Marine Macroaggregates

Nives Kovač,a* Jadran Faganeli,a Oliver Bajt,a Boris Šket,b Angela Šurca Vuk,c Boris Orelc and Patricija Mozetiča

aMarine Biological  Station, National Institute of Biology, Fornače 41, SI-6330 Piran, Slovenia
bFaculty of Chemistry and Chemical Technology, University of Ljubljana, Askerčeva 5, SI-1000 Ljubljana, Slovenia
cNational Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia

Solid-state 13C NMR and FTIR spectroscopy were applied to establish the chemical features of bulk mucous macroaggregates of phytoplanktonic origin at two different depths, surface and bottom, in the Gulf of Trieste (northern Adriatic Sea) in June 2000. The bottom sample was poor in organic matter (5% Corg, 0.5% Ntot) compared to the surface sample (17.2% Corg, 1.2% Ntot) and contained mostly senescent and degraded cells. An increase in mineral particles (quartz and calcite) was also evident. This was due to the degradation of the organic fraction and the contribution of bottom sediment resuspension. The 13C-NMR–based estimate showed the approximate composition of sampled macroagregates: 26% aliphatic C, 14% O/N alkyl structures, 39% carbohydrates, 15% aromatic and olefinic C and 6% ester and/or amide C. From the solid-state 13C NMR spectrum of the sedimented macroaggregate revealed the preservation of aliphatic (lipidic) material and a portion of the labile nitrogen-containing compounds.

Key words: macroaggregates, FTIR, solid-state 13C NMR, northern Adriatic