Using HPLC pigment analysis to investigate phytoplankton taxonomy: the importance of knowing your species

Abstract

Phytoplankton microscopic enumerations and HPLC analyses of their pigments were performed weekly for a complete year at a coastal station in the English Channel. The taxonomic composition of the phytoplankton community was assessed using the HPLC results combined with the mathematical tool CHEMTAX in two different ways. Firstly, without using the species level taxonomic information obtained at the microscopic level (blind analyses), and secondly by including the information from the microscopic taxonomic analysis (directed analyses). The results indicate that, due to the particular pigment composition of some species (for example, the dinoflagellate, Karenia mikimotoi and the haptophyte, Phaeocystis pouchetii), a blind analysis would result in very significant errors in the taxonomic determination of the bloom events at this station. Major blooms of Karenia mikimotoi and P. pouchetii were mistaken for blooms of diatoms on the basis of a blind HPLC-CHEMTAX analysis. Only with the information from the microscopic observations was it possible to obtain an accurate representation of the phytoplankton community.

Microzooplankton grazing and phytoplankton growth in marine mesocosms with increased CO<sub>2</sub> levels

“…(Antajan et al, 2004;Irigoien et al, 2004). We compared the pigment data to microscopic counts (data not shown), as well as to plankton analyses from the mesocosms (Egge et al, 2007;, and found it to be consistent.…”

Mesozooplankton selective feeding in subtropical coastal waters as revealed by HPLC pigment analysis

“…Successful estimates of phytoplankton community structure from pigment data using the CHEMTAX program rely largely on the initial choice of pigment to chl a ratios, which can vary with species (e.g. Jeffrey & Wright 1994, Irigoien et al 2004), irradiance and nutrients (e.g. Goericke & Montoya 1998, Henriksen et al 2002, Rodríguez et al 2006.…”

“…Previously, better agreement between the 2 techniques was found for large diatoms than for small flagellates (Rodríguez et al 2002, Garribotti et al 2003, Llewellyn et al 2005. The discrepancy between the 2 approaches was probably caused by ambiguity of some chemotaxonomic pigments (Irigoien et al 2004), uncertain bio-volume to carbon conversion factors (Montagnes et al 1994), or simply the large variation in carbon-to-chlorophyll ratios among different dominant species and different growth stages.One possible issue that may cause bias and inaccurate estimation of taxon-specific mesozooplankton grazing rates in our approach is the inclusion of fecal materials that contain partially digested pigment in the samples. While recognizing that pigment degradation and alteration are likely to occur in the gut of herbivorous zooplankton and different marker pigments may be degraded to a different extent in the fecal pellets (e.g.…”

Phytoplankton assemblage changes during decadal decreases in nitrogen loadings to the urbanized Long Island Sound estuary, USA

“…Thus derived chl a contribution from the non-diatom ensemble was summed and considered as an additional statistical variable. The CHEMTAX method has previously been shown to underestimate the relative abundances of certain dinoflagellates and haptophytes due to unique pigment markers in some species of these groups (Irigoien et al 2004). Furthermore, dia toms have a higher chl a:C ratio than other phytoplankton, and chl a estimates derived from the Chemtax method may overestimate their biomass (Llewellyn et al 2005).…”