Table 2

Chemical composition of bacterially derived DOM in the glucose and glutamate experiments. All are the mean of duplicate-bottle experiments, except for the data indicated by asterisks, which were obtained from single bottles. The mean deviation of replicates was 0.9 μM for DOC, 0.2 μM for DON, 2 for C/N ratio, and 1 to 2% of DOC, DON, THAS, and THAA compositions. The “uncharacterized” fraction in the glucose experiment is estimated as the difference between the total DOC and the DOC accounted for as THNS+THAS+THAA, and between the total DON and the DON accounted for as THAA+THAS, except for the data after 1 year, in which THNS was not included (data in parenthesis). The “uncharacterized” fraction in the glutamate experiment is based only on THAA, because THNS and THAS were not measured (indicated by “nm”).

Chemical compositionInitial substrate
GlucoseGlutamate
Incubation time (days)Incubation time (days)
247365249560
Concentration of the bulk DOM (μM)
DOC301816 111813149.0
DON1.00.70.6  1.23.1 2.41.50.7
DOC composition (% as)
THNS2.54.95.9nmnmnmnmnm
THAS0.71.41.5  3.8nmnmnmnm
THAA2.54.33.7  2.51318* 123.1
Uncharacterized948989(94)8782* 8897
DON composition (% as)
THAS3.45.56.6 5.6nmnmnmnm
THAA222927 6.41531* 3311
Uncharacterized756667888569* 6789
C:N molar ratio
Bulk322628 8.95.1 5.79.313
Total characterized7.57.99.2(4.6)3.5 3.13.33.6
Uncharacterized413737(10)5.4 6.3* 1214
THAS composition (mole %)
GalN20263133nmnmnmnm
GlcN55505667nmnmnmnm
MA2624120nmnmnmnm
THAA composition (mole %)
Acidic2627213026121728
Basic121011118 678
Neutral2327314124563646
Hydrophobic3836371841274018