Highly Unsaturated Fatty Acids: The Missing Link in Aquatic Food Webs?

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9615888 Goldman In aquatic food webs, the flow of energy across the plant-herbivore interface is highly variable and the factors controlling the efficiency at which phytoplankton is converted to zooplankton biomass are poorly understood. The objective of this research is to improve understanding of processes that regulate efficiency of energy transfer, secondary production and strength of trophic cascades. The central hypothesis is that the highly unsaturated fatty acid (HUFA) content of seston strongly influences these processes. The biological significance of HUFA is a promising and rapidly developing area of research in a very wide variety of fields including animal cell membrane physiology, hormonal synthesis, human health and nutrition, and aquaculture. HUFA are important for two principal reasons: first, they have a large impact on animal cell membrane fluidity and are precursors for eicosanoids (which includes prostaglandins, luekotrienes and other animal hormones), and second, they are only produced by plants. Unlike many lipids, HUFA are not used for energy storage. These facts lead to the specific prediction that during periods when the seston is dominated by phytoplankton with high HUFA content, coupling will be tight and energy transfer will be efficient, while during periods with low-HUFA seston, coupling will be weak. This pattern has already been observed in comparisons among lake types, with very weak coupling in lakes dominated by HUFA-poor cyanobacteria and tight coupling in lakes dominated by HUFA-rich diatoms and cryptophytes. In this research, controls on these patterns will be tested in a series of experiments to examine the relationship between seston elemental and biochemical composition and zooplankton growth and growth efficiency.