Diatom fatty acid biomarkers indicate growth rates in Antarctic krill

We investigated the relationship between nutritional condition (levels of specific fatty acids) and growth increment (percentage growth per intermoult period, percentage IMP-1) for Antarctic krill (Euphausia superba) collected from the vicinity of South Georgia in the austral summer 2002. There were correlations between percentage IMP-1 and the concentration (gram: gram dry weight) of the diatom biomarker fatty acids, 16: 4(n-1) and 20: 5(n-3) in tissues of individual krill, suggesting that the abundance of diatoms in the environment of the krill in the intermoult period prior to moulting was a key determinant of change in body length, a proxy for growth. This substantiates the view that diatoms are crucial for supporting high growth rates of krill, either as a direct food source or, indirectly, by enhancing production of microzooplankton and mesozooplankton based food webs.

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