Chapter

Lipids in Freshwater Ecosystems

pp 45-70

Irradiance and Lipid Production in Natural Algal Populations

  • Bruce C. Wainman
  • , Ralph E. H. Smith
  • , Hakumat Rai
  • , John A. Furgal

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Abstract

Lipids are important to aquatic ecosystems, as essential dietary components for animals (including some of economic importance in both wild and cultured food production) (Olsen, this volume), as vectors for movement of hydrophobic materials (including many important contaminants), and as the proximate agents of toxicity in a variety of organisms (Landrum and Fisher, this volume). Microalgae, including phytoplankton and attached forms such as ice algae and periphyton, are major producers of aquatic lipids. A substantial body of measurements of lipid synthesis by natural populations of microalgae has developed, thanks largely to the relative ease with which 14C and simple chemical extraction protocols can be applied to measure the intracellular allocation of recent photosynthate (Morris et al., 1981,Morris et al., 1974; ). In practice, the term photosynthate here refers to carbon incorporated (and therefore labeled) within the span of typical primary production experiments (usually 4-24 hours). Such measurements have revealed substantial variation in the synthesis and relative allocation of photosynthate to lipids, which may be related to environmental and taxonomic factors (Madariaga, 1992; Wainman and Lean, 1992).