Biogenic components of estuarine and marine humic materials

Abstract

The nature of the biogenic components in dissolved humic substances from the Beaulieu estuary (Hampshire, U.K.) and coastal waters (The Solent, Hampshire, U.K.) has been studied. Humic materials were extracted from the water using a macroreticular resin (Amberlite XAD-8), and carbohydrate, lipid and amino acid analyses were performed on the resulting samples.

A procedure was developed for the analysis of neutral sugars by on-column capillary gas chromatography, and this was applied to the determination of monosaccharides in aquatic humic substances. Glucose, galactose, arabinose, rhamnose and mannose were found to be the major sugars in these materials, with xylose and ribose detected at lower levels. Fucose and lyxose were also present. The estuarine distribution of these compounds supported a decreasing terrestrial and increasing planktonic input to these materials with increasing salinity.

Investigations on the lipid content of the humic material were performed by gas chromatographic analysis of their methyl ester derivatives. Despite significant contamination, certain unsaturated fatty acids, namely palmitoleic and oleic acids, were identified in several samples. Linoleic acid was also found in one instance.

Amino acids were studied by hydrolysis of the humic materials, followed by thin-layer chromatography. Quantitation was performed using an amino acid analyser. The amino acid content of the humic substances tended to increase in the summer months but no trends were noted in the patterns of the individual amino acids, either seasonally or between the three sampling sites. Glycine was found to be the major amino acid in most samples, with histidine, aspartic acid, glutamic acid and alanine contributing significantly in selected samples. Lower levels of arginine, cystine, leucine, isoleucine, lysine, methionine, phenylalanine, serine, threonine, tryptophan, tyrosine and valine were also present.

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