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 foc 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 oflipid extraction, lipid fractionation, fany 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:​H₂O, followed by fractionation on silica gel and FAME formation with SF) gave optimal recoveries. PicoIinyl derivatives offatty acids are useful in structure determination with mass spectrometry and a new transesterification method for their synthesis was developed. In addition, the treatment ofsamples with high lipase activities with boiling water was effective in deactivating those enzymes and resulted in lower levels offree fatty acids, a breakdown product.

Combinations of all these melhods were applied 10 biogeochemical and aquaculture projedS. In the two very different environments ofTrinity Bay and Barred bland Cove, the fatty acid composition of plankton and sediment trap samples was characterized by high levels of polyunsaturated fany acids (20-50% of total fany acids), indicating a substanlial marine phytoplankton source, particularly diatoms. However, much higher levels ofterrestrial 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 approrimating the bivalve's requirements. Another aquaculture interest is in establishing fatty acid biomarkers that may be used 10 indicate the presence of toxic algae. To this end, the fatty acid composition of the toric 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 potentiaJ in di1ferentiating those Pseudo-nitzschia species from other diatoms. Thus, accurate analysis offatty acids in cold water marine samples can provide insights into biogeochemical processes, food web connections and the chemotaxonomy ofloxic phytoplankton.