Global trends in the fluorescence characteristics and distribution of marine dissolved organic matter

TY - JOUR

T1 - Global trends in the fluorescence characteristics and distribution of marine dissolved organic matter

AU - Jørgensen, Linda

AU - Stedmon, Colin

AU - Kragh, Theis

AU - Markager, Stiig

AU - Middelboe, Mathias

AU - Søndergaard, Morten

PY - 2011/9/20

Y1 - 2011/9/20

N2 - A fraction of dissolved organic matter (DOM) is able to fluoresce. This ability has been used in the present study to investigate the characteristics and distribution of different DOM fractions. A unique global dataset revealed seven different fluorescent fractions of DOM: two humic-like, four amino acid-like and one chemically uncharacterized. The spectral characteristics of the amino acid-like fractions resemble those of pure tryptophan, tyrosine and phenylalanine. The fluorescence intensities of these amino acid-like fractions are highest in the surface waters, rapidly decreasing with depth and at a constant low level in the bathypelagic layer. Such profiles indicate that amino acid-like DOM is linked to surface water production. From calibration curves we estimated the mean surface water concentrations of tryptophan and tyrosine to be 12.5 and ~ 15.9 nmol L- 1, respectively, while mean deep water concentrations are 5.1 and ~ 6.5 nmol L- 1. The fluorescence intensities of the humic-like DOM fractions were low in the surface layer, rapidly increasing in the mesopelagic layer and at constant high level in the bathypelagic layer. The low fluorescence intensities observed in the surface layer indicate the quantitative importance of photochemical degradation as a sink of the humic-like compounds. In the dark ocean (below 200 m), significant linear relationships between humic-like DOM fluorescence and microbial activity (apparent oxygen utilization, NO3- and PO43-) were found. These observations imply a link to dark ocean microbial remineralization and indicate that the major source of humic-like compounds is microbial turnover of organic matter. The results of the present study show that the distribution of the humic-like DOM fractions is a balance between supply from continental run off, net microbial production and photochemical removal in surface waters

AB - A fraction of dissolved organic matter (DOM) is able to fluoresce. This ability has been used in the present study to investigate the characteristics and distribution of different DOM fractions. A unique global dataset revealed seven different fluorescent fractions of DOM: two humic-like, four amino acid-like and one chemically uncharacterized. The spectral characteristics of the amino acid-like fractions resemble those of pure tryptophan, tyrosine and phenylalanine. The fluorescence intensities of these amino acid-like fractions are highest in the surface waters, rapidly decreasing with depth and at a constant low level in the bathypelagic layer. Such profiles indicate that amino acid-like DOM is linked to surface water production. From calibration curves we estimated the mean surface water concentrations of tryptophan and tyrosine to be 12.5 and ~ 15.9 nmol L- 1, respectively, while mean deep water concentrations are 5.1 and ~ 6.5 nmol L- 1. The fluorescence intensities of the humic-like DOM fractions were low in the surface layer, rapidly increasing in the mesopelagic layer and at constant high level in the bathypelagic layer. The low fluorescence intensities observed in the surface layer indicate the quantitative importance of photochemical degradation as a sink of the humic-like compounds. In the dark ocean (below 200 m), significant linear relationships between humic-like DOM fluorescence and microbial activity (apparent oxygen utilization, NO3- and PO43-) were found. These observations imply a link to dark ocean microbial remineralization and indicate that the major source of humic-like compounds is microbial turnover of organic matter. The results of the present study show that the distribution of the humic-like DOM fractions is a balance between supply from continental run off, net microbial production and photochemical removal in surface waters

U2 - 10.1016/j.marchem.2011.05.002

DO - 10.1016/j.marchem.2011.05.002

M3 - Journal article

SN - 0304-4203

VL - 126

SP - 139

EP - 148

JO - Marine Chemistry

JF - Marine Chemistry

IS - 1-4

ER -