Sequestration of organic nitro gen in the sapropel from Mangrove Lake, Bermuda

Humic isoJates from different layers of an organic-matter-rich algal sapropel from Mangrove Lake, Bennuda, were subjected to solid-state 15N nuclear magnetic resonance (NMR) spectroscopy in crder to reveal chemical structural interrelationships tbat allow delineation of diagenetic pathways. Amide-N, most likely from peptide-like material, \Vas found to represent the main organic nitrogen fonu in all humic fractions at all depths of the sapropel. Amides were also idenlified in lhe residues from 6 M Hel hydrolysis of lhe alkaline insoluble exlracl (formerly called humin). These results indicate that sorne peptide-like material resists both alkaline and acid hydrolysis. We suggest that the chemical, and also the biological recalcitrance of peptide-like material, is related to encapsulation into the paraffinic network of algaenans. Being hydrophobic in nature, algaenan biomacromolecules may represent an effective means of protection against the attack of hydrophilic enzymes and aqueous extraction solutions.