Quantitative interpretation of chemotaxonomic pigment data

<p>The use of pigments for the quantitative chemotaxonomic analysis of phytoplankton populations began in the 1970s when thin layer chromatography revealed a large diversity of pigments in the phytoplankton (Jeffrey, 1974), many of which appeared to be restricted to certain algal taxa and could be sensitively detected even in the presence of protozoa, bacteria and detritus, in which they are absent. Since that time, developments in phytoplankton systematics, particularly through DNA analysis (e.g. Karlson <i>et al</i>., 2010), have revealed a much greater taxonomic diversity in phytoplankton than previously imagined, while simultaneous improvements in chromatography have led to the identification of >70 pigments in 45 pigment patterns (tabulated in Jeffrey <i>et al</i>., Chapter 1, this volume). This provides substantial additional power in pigment analysis but also hugely complicates interpretation of pigment data. Relatively few pigments are now regarded as unambiguous markers – most are distributed across several taxa.</p> The pigment composition of microalgae is strongly influenced by several environmental factors that complicate interpretation of field data. A full synopsis is beyond the scope of this chapter, but known influences and key references include: irradiance (Johnsen <i>et al</i>., 1994; Goericke and Montoya, 1998; Schlüter <i>et al</i>., 2000; Rodríguez <i>et al</i>., 2006a), spectral distribution of light (Wood, 1985), ultraviolet (Gerber and Häder, 1994); day length (Sakshaug and Andresen, 1986), diurnal cycle (Tukaj <i>et al</i>., 2003), nutrient status (Goericke and Montoya, 1998; Henriksen <i>et al</i>., 2002; Stæhr <i>et al</i>., 2004; Hou <i>et al</i>., 2007), iron concentration (van Leeuwe and Stefels, 1998; DiTullio <i>et al</i>., 2007; Hopkinson <i>et al</i>., 2007), mixing regime (Brunet <i>et al</i>., 2003; Thompson <i>et al</i>., 2007) and growth phase (Wilhelm and Manns, 1991; Henriksen <i>et al</i>., 2002; Redalje <i>et al</i>., 2008). The pigment content can vary qualitatively between members of a genus, or even between strains of single species (Stolte <i>et al</i>., 2000; Zapata <i>et al</i>., 2004; Laza-Martinez <i>et al</i>., 2007). Thus the pigment content of a field population cannot be accurately predicted even if one knows the species present.