Amino acid remineralization and organic matter lability in Chilean coastal sediments

Abstract

The spatial distribution of proteinaceous amino acids was investigated in Chilean coastal surface sediments. Proteinaceous amino acids, measured as total hydrolyzed amino acids (THAA), were in the range 37–1335 μmol THAA-N gdw−1 and accounted for 6–70% of total nitrogen in surface sediments. Beggiatoa or Thioploca, motile, filamentous bacteria present in sediments with low oxygen bottom waters, may be a source of the non-protein amino acid, β-aminoglutaric acid. Mineralization of sedimentary THAA accounted for about one quarter of the ammonium production measured in these sampling sites. Reactivity of organic matter in these coastal sediments was assessed using a Degradation Index developed by Dauwe and Middelburg (1998; Limnology and Oceanography 43, 782–798) and Dauwe et al. (1999; Limnology and Oceanography 44, 1809–1814). Both production of ammonium and mineralization of amino acids follow a consistent trend with this index. Thus, we can relate the production of ammonium and mineralization of amino acids to the diagenetic state of the sediment.