Organic biogeochemistry of a hypereutrophic tropical, freshwater lake — Part 1: particle associated and dissolved lipids

Lipid components in both the dissolved and particle associated phases were analyzed in several samples taken at different depths in the water column of a hypereutrophic, tropical, freshwater lake (Lake Valencia, Venezuela). Quantitatively and qualitatively, the lipid fraction was found to vary with depth. Early diagenetic changes were clearly observed for several lipid classes in both stratified and mixed water conditions. The origin of the organic matter was primarily autochthonous (planktonic and bacterial). The dissolved lipid fraction was found to contribute a significant percentage of the total lipids in the lake. High primary productivity of specific species of phytoplanktonic organisms in the lake water resulted in an abundance of some lipid classes which are usually assigned a terrestrial (allochthonous) origin, but in this case seem to be microbially derived.