Fatty acid biomarkers in a cold water marine environment.

摘要

Fatty acids are of great interest in a variety of disciplines, including oceanography, geochemistry, food science and biochemistry, and this has led to the development of diverse methods for their determination. This study was undertaken to establish optimal methods for fatty acid extraction and analysis and to apply those methods to samples in the marine environment. Several methods of lipid extraction, lipid fractionation, fatty acid methyl ester (FAME) formation and picolinyl ester synthesis were examined. For most sample types, a biphasic extraction mixture of 8:4:3 CHCl3:MeOH:H 2O, followed by fractionation on silica gel and FAME formation with BF3 gave optimal recoveries. Picolinyl derivatives of fatty acids are useful in structure determination with mass spectrometry and a new transesterification method for their synthesis was developed. In addition, the treatment of samples with high lipase activities with boiling water was effective in deactivating those enzymes and resulted in lower levels of free fatty acids, a breakdown product.; Combinations of all these methods were applied to biogeochemical and aquaculture projects. In the two very different environments of Trinity Bay and Barred Island Cove, the fatty acid composition of plankton and sediment trap samples was characterized by high levels of polyunsaturated fatty acids (20--50% of total fatty acids), indicating a substantial marine phytoplankton source, particularly diatoms. However, much higher levels of terrestrial plant and bacterial indicators in Barred Island Cove as compared to Trinity Bay illustrated the differences in the two environments. The fatty acid composition of blue mussels from Barred Island Cove were also compared to that of natural phytoplankton populations. In terms of fatty acid nutritional needs, the phytoplankton seemed to be providing fatty acids in proportions closely approximating the bivalve's requirements. Another aquaculture interest is in establishing fatty acid biomarkers that may be used to indicate the presence of toxic algae. To this end, the fatty acid composition of the toxic diatoms Pseudo-nitzschia multiseries and P. pungens was determined. High levels of 16:4n-1 (>7%) were found in both species and that fatty acid may have potential in differentiating those Pseudo-nitzschia species from other diatoms. Thus, accurate analysis of fatty acids in cold water marine samples can provide insights into biogeochemical processes, food web connections and the chemotaxonomy of toxic phytoplankton.