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Biologically utilizable dissolved organic compounds,including dissolved organic carbon (DOC),dissolved carbohydrates (DCHO) and dissolved free amino acids (DFAA) were analyzed in filtered surface seawater samples collected at 19 stations in Jiaozhou Bay,China,on June 3,2007.In these samples,concentrations of DOC,dissolved free carbohydrates (DFCHO),dissolved combined carbohydrates (DCCHO),total dissolved carbohydrates (TDCHO) and total dissolved free amino acids (TDFAA) ranged from 141.7 to 191.1 μmol C/L,1.98 to 18.18 μmol C/L,5.04 to 24.90 μmol C/L,14.52 to 30.36 μmol C/L,and 1.83 to 11.89 μmol C/L,respectively.As a major component of the dissolved carbohydrates,the concentrations of DCCHO were about three times higher than those of DFCHO.Three major constituents of the DFAA were threonine (23.0±5.7 mol%),glutamic acid (16.6±3.2 mol%) and arginine (9.1±3.3 mol%).Based on the composition of DFAA,a molar C:N ratio of 3.60±0.75 in DFAA was derived,indicating longer carbon chains in the amino acids.DCCHO (8.1%) was the most abundant fraction of DOM in most samples,followed by DFCHO (4.8%) and TDFAA (2.7%).These DOM concentrations displayed a decreasing trend from the coast to the central region.Significant correlations were found between the DCCHO and DFCHO concentrations (r=-0.724,n=19,P<0.001) and the DCCHO and TDCHO concentrations (r=0.506,n=19,P=0.027).
Biologically utilizable dissolved organic carbons (DOC), dissolved carbohydrates (DCHO) and dissolved free amino acids (DFAA) were analyzed in filtered surface seawater samples collected at 19 stations in Jiaozhou Bay, China, on June 3, 2007. In these samples, concentrations of DOC, dissolved free carbohydrates (DCCHO), total dissolved carbohydrates (TDCHO) and total dissolved free amino acids (TDFAA) ranged from 141.7 to 191.1 μmol C / L, 1.98 to 18.18 the concentrations of DCCHO were about three times higher than that of DCMO, respectively. As a major component of the soluble carbohydrates, the concentrations of DCCHO were about three times higher than those of DFCHO.Three major constituents of the DFAA were threonine (23.0 ± 5.7 mol%), glutamic acid (16.6 ± 3.2 mol%) and arginine (9.1 ± 3.3 mol%). Based on the composition of DFAA, a molar C : N ratio of 3.60 ± 0.75 in DFAA derived, indicating longer carbon chain s in the amino acids. DCCHO (8.1%) was the most abundant fraction of DOM in most samples, followed by DFCHO (4.8%) and TDFAA (2.7%). These DOM concentrations showed a decreasing trend from the coast to the central region .Significant correlations were found between the DCCHO and DFCHO concentrations (r = -0.724, n = 19, P <0.001) and the DCCHO and TDCHO concentrations (r = 0.506, n = 19, P = 0.027).