Pigment ratios and phytoplankton assessment in northern Wisconsin lakes

Abstract

Nine lakes in northern Wisconsin were sampled from February through September 1996, and HPLC analysis of water column pigments was carried out on epilimnetic seston. Pigment distributions were evaluated throughout the water column during summer in Crystal Lake and Little Rock Lake. The purpose of our study was to investigate the use of phytopigments as markers of the main taxonomic groups of algae. As a first approach, multiple regression of marker pigments against chlorophyll a (chl a ) was used to derive the best linear combination of the main xanthophylls (peridinin, fucoxanthin, alloxanthin, lutein, and zeaxanthin). A significant regression equation ( r 2 ϭ 0.98) was obtained for epilimnion data. The good fit indicates that the chl a :xanthophyll ratios were fairly constant in the epilimnion of the nine lakes over time. Chlorophyll a recalculated from the main xanthophylls in each sample showed good agreement with measured chl a in epilimnetic waters. A second approach used the CHEMTAX program to analyze the same data set. CHEMTAX provided estimates of chl a biomass for all algal classes and allowed distinction between diatoms and chrysophytes, and between chlorophytes and euglenophytes. These results showed a reasonably good agreement with biomass estimates from microscope counts, despite uncertainties associated with differences in sampling procedure. Changes of pigment ratios over time in the epilimnetic waters were also investigated, as well as differences between surface and deep samples of Little Rock Lake and Crystal Lake. We found evidence that changes in the ratio of photoprotective pigments to chl a occurred as a response to changes in light climate. Changes were also observed for certain light-harvesting pigments. The comparison between multiple regression and CHEMTAX analyses for inferring chl a biomass from concentrations of marker pigments highlighted the need to take account of variations in pigment ratio, as well as the need to acquire additional data on the pigment composition of planktonic algae.

Patterns of major photosynthetic pigments in freshwater algae. 2. Dinophyta, Euglenophyta, Chlorophyceae and Charales

“…In addition to spectrophotometers (UV-VIS) and fluorescence detectors, DAD's are increasingly used in pigment analysis (Wright et al 1991, Almela et al 1992, Epler et al 1992, Kraay et al 1992, van Heukelem 1992, Tsavalos et al 1993, Jeffrey et al 1997, Descy et al 2000. Initially DAD's were developed for the UV range (Meyer 1999).…”

“…Ansotegui et al (2001) calculated by means of a multifactorial approach (CHEMTAX, Mackey et al 1996) around 1,5 -3,0 % neo-, 4 to 23 % diadinoxanthin and 41 -124 % chl-b on a weight basis of chl-a. The same approach was used by Descy et al (2000), who estimated 20 % diadinoxanthin and 31 to 39 % chl-b per unit chl-a, neoxanthin was not detected. Unfortunately, the initial pigment ratios which are required for CHEMTAX (factor analysis and a steepest descent algorithm) were not cited in these studies.…”

“…For multivariate approaches on algal quantification by means of pigments like multiple linear regression (eg. Woitke et al 1996, Descy et al 2000 or factor analysis (Mackey et al 1996, Wright et al 1996, Descy et al 2000, Ansotegui et al 2001, basic data sets of carotenoid contents are required. Some quantitative pigment data are contributed in the present study.…”

Variability of phytoplankton pigment ratios across aquatic environments

“…The use of marker pigments to identify and quantify the various algal groups of phytoplankton has been widely and successfully used in marine, estuarine and references therein), freshwater environments (Woitke et al, 1996;Yacobi et al, 1996;Edelkraut et al, 1997;Descy et al, 2000Descy et al, , 2005Fietz & Nicklisch, 2004Buchaca et al, 2005) and even for the study of photosynthetic bacteria (Steenbergen et al, 1989;Hurley & Watras, 1991;Vila et al, 1996;Goericke, 2002). However, as the biomass estimation of algal groups is derived from pigment concentrations in the water column by calculations based on marker pigment:chlorophyll a (chl a hereafter) ratios, the technique is prone to errors related to changes in the cell pigment content, which may result from acclimation to the light climate and from nutrient deficiency.…”

“…The datasets were either from previously published studies dealing with phytoplankton classes assessment using CHEMTAX (e.g. Descy et al, 2000), or from reprocessing of published data (e.g. Descy et al, 2005), or from new, unpublished pigment data.…”