Diatoms and fatty acid production in Arctic and estuarine ecosystems—a reassessment of marine food webs, with a focus on the timing of shorebird migration

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This review highlights diatoms and their production of fatty acids at Arctic ice edges and temperate estuaries as strategic in initiating high spring productivity. As important as their energy production is their synthesis de novo of omega-3 long-chain polyunsaturated fatty acids (LCPUFAs), which are bioactive molecules fundamental to maintaining ecosystem processes, and are necessary for reproduction and growth for the entire marine food web. Without these fatty acids, consumers can suffer poor reproduction and growth even with sufficient energy intake, and shorebirds may need LCPUFAs for nonstop long-hop migration. Timing of high energy fatty acid and LCPUFA production by diatoms coincides with growth and reproduction of consumer populations, with the arrival of seabirds in the Arctic and staging of shorebirds in estuaries. The switch from diatom production of carbohydrates to fatty acids is triggered by changes in chemical and physical environmental factors, which can be muted by factors such as climate change or habitat modification. Higher ocean temperatures and lower pH from climate change alters the ability of diatoms to make LCPUFAs, and habitat degradation reduces the numbers of diatoms in the area, subsequently reducing the amounts of LCPUFA produced. Changes in LCPUFA output could impact functionality of ice-edge and estuarine ecosystems, impacting shorebird migration and consumer productivity. Research is scarce on marine consumer reproduction and growth comparing quantity vs. quality of ingested saturated, monounsaturated, and omega-3 LCPUFAs, and nonexistent for seabirds and shorebirds. Future studies of marine food webs should include the role of diatoms and their contribution of not just energy, but also LCPUFAs to the food web.