Combined fatty acids and amino acids in the dissolved + colloidal and particulate fractions of the waters from a dystrophic lake

The combined amino acids and fatty acids in the dissolved + colloidal and particulate phases of the waters from a dystrophic lake have been studied. The former encompass 0.9–1.5% of the dissolved organic carbon (DOC) and about 10% of the particulate organic carbon (POC). The latter are minor compounds representing 0.023–0.067% and about 0.3% of DOC and POC, respectively. The high phase distribution coefficients of all individual components are indicative of the fatty acid and amino acid association with organic materials that are predominant in the suspended particles. Furthermore, their similar coefficients point to a rather uniform phase distribution pattern which is characteristic of partitioning between the particulate and the colloidal fraction. Despite this general uniformity, two major distinct features have been observed when comparing the composition of the two phases. These concern the dominance of glycine in the dissolved + colloidal fraction and the high proportion of unsaturated fatty acids in the particulate matter. The differences correspond with the predominance of algal and terrestrial inputs in the particulate fraction and with the selective enrichment of microbial components in the dissolved + colloidal phase. The higher proportion of microbial fatty acids in this fraction appears to be a characteristic feature of this dystrophic lake when compared with the phase-dependent fatty acid distributions of riverine and marine waters previously studied.