Linking diagenetic alteration of amino acids and bulk organic matter reactivity

Abstract

Examination of amino acids in particulate samples from a variety of marine environments (fresh phytoplankton to deep‐sea sediments) revealed systematic compositional changes upon progressive degradation. These consistent trends have been used to derive a quantitative degradation index (DI) that is directly related to the reactivity of the organic material, as indicated by its lability to enzymatic decay and its first‐order degradation rate constant. This direct link between molecular composition and degradation rate allows us to quantify the quality of organic matter based solely on its chemical composition.

Seasonal variability of denitrification efficiency in northern salt marshes: An example from the St. Lawrence Estuary

“…THAA concentrations measured in triplicate on one core sampled during summer time (early in August 2005), reached 55.71 ± 5.61 µmol g -1 (n = 3). The average DI value calculated for Pointe-au-Père salt marsh sediment (-0.67 ± 0.02; n = 3) was below the range of values usually obtained for coastal sediments (from -0.35 to 1.01) as reported by Dauwe et al, (1999) indicating that organic matter in sediment was in an advanced state of decomposition (Table 1).…”

“…Diagenetic alteration of sedimentary amino acids was assessed using the Degradation Index (DI) developed by Dauwe and Middelburg (1998) and Dauwe et al (1999). This index is based on the first axis of a Principal Component Analysis (PCA) of the amino acid composition and summarizes, in one variable, the relative cumulative variation of 14 amino acids (aspartic acid, glutamic acid, serine, histidine, thréonine, arginine, glycine, tyrosine, alanine, méthionine, valine, phenylalanine, isoleucine and leucine).…”

“…DI values were calculated from amino acids average molar concentration, standard deviation and predetermined coefficient factors (i.e. first axis of the Principal Component Analysis from the comprehensive data set of Dauwe et al, 1999). The DI sign indicates a depletion (-) or an enrichment (+) of labile organic nitrogen protein in sediment.…”

Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids

“…Molar percentages of individual AA are standardised by the mean and standard deviations of the 28-sample data set. The DI then integrates the AA weighed by the factor coefficients for the first axis of the principal component analyses (PCA) of Dauwe et al (1999) according to the formula:…”

“…The molar percentages of the 14 protein AA were used to calculate the degradation index (DI) developed by Dauwe and Middelburg (1998) and Dauwe et al (1999) which assesses the diagenetic alteration of a sample by comparing it to a set of 28 samples of different degradation states and environments. Molar percentages of individual AA are standardised by the mean and standard deviations of the 28-sample data set.…”