Comparing microscopic counts and pigment analyses in 46 phytoplankton communities from lakes of different trophic state

Abstract

00000 ăWOS:000386021300002International audience1. Comparison between algal pigment analyses using HPLC and subsequent CHEMTAX analysis with microscopic counts from different lakes ranging from ultra-oligotrophic to eutrophic allowed testing of pigment: chlorophyll a ratios for lakes of different trophic conditions. Microscopic counts and pigment analyses were positively correlated for all groups except for the chrysophytes. 2. When examining the oligotrophic lakes only, microscopic analyses and pigment analyses of chrysophytes were positively correlated, which showed that the oligotrophic pigment ratios were well suited for determining the abundance of the chrysophytes in oligotrophic lakes. In the eutrophic lakes, where chrysophytes constituted less than 10% of the biomass, the weak correlation was most likely related to counting inaccuracies. 3. Chrysophytes, generally indicative of oligotrophic conditions, were three times more abundant in the oligotrophic lakes. They constituted 28% of the total phytoplankton biomass as chlorophyll a measured by the pigment method and 26% of the total phytoplankton biomass measured as biovolume by microscopy. In mesotrophic/eutrophic lakes, chrysophytes constituted only 9% (pigment method) and 8% (microscopy). 4. Similarity analyses comparing the results of these two methods on functional group level documented the high accuracy of the pigment method in detecting all the functional groups present. 5. The results of the pigment analyses showed a more even composition of phytoplankton groups than found by microscopy, where often one or two of the less abundant groups were absent or only sporadically present. The Shannon's diversity index, H', for functional groups determined from results of the pigment method were higher than the H' values based on microscopic counts, confirming a more continuous composition of the phytoplankton groups when detected by the pigment method. The pigment method was found to be a useful alternative, which supplemented microscopic counts

Characterization of phytoplankton by pigment analysis and the detection of toxic cyanobacteria in reservoirs with aquaculture production

“…Because small and overlooked species may be ignored by microscopy, actual species diversity may be more accurately determined by pigment analysis. This was confirmed by analysis of phytoplankton species in more than 40 lakes, where a higher Shannon's diversity index was determined by pigment analyses than by microscopy counting (Schlüter et al 2016). An additional advantage of the pigment method is that rare species in low densities can be identified but may be overlooked by microscopy.…”

“…The filters were sonicated in an ice-cool sonication bath for 10 min, extracted further at 4°C for 20 h and mixed using a vortex mixer for 10 s. The filters and cell debris were filtered from the extracts into HPLC vials using disposable syringes and 0.2 µm Teflon syringe filters. Pigment analyses were carried out according to Schlüter et al (2016) using the Van Heukelem & Thomas (2001) method, but with an adjusted pump gradient to optimise the pigment resolution. More than 30 different phytoplankton caro tenoids and chlorophylls can be detected.…”

Taxonomic Shift Over a Phosphorus Gradient Affects the Stoichiometry and Fatty Acid Composition of Stream Periphyton

“…Microscopic counts allowed us to identify the algal classes present in the samples (viz., diatoms, chlorophytes, and cyanobacteria), thus the pigment ratio table for CHEMTAX was adjusted accordingly. The pigment/chlorophyll a ratio matrix from Schlüter et al (2016) was used as initial ratio matrix, from which 60 different ratio matrices were generated for each treatment. Of these, the six matrices (10%) with the lowest residual root mean square were averaged to create a new input ratio matrix, which was run repeatedly until the ratios and root mean squares were stable.…”

Metatranscriptomics From a Small Aquatic System: Microeukaryotic Community Functions Through the Diurnal Cycle

“…Pigments were identified via comparisons of retention times with those of pure standards DHI Water (Høersholm, Denmark). The pigment content from each sample was used to estimate the contribution of different phytoplankton groups to the total chlorophyll a, using the software CHEMTAX (Mackey et al, 1996), and initial matrices with pigment:chl-a ratios previously described for freshwater systems (Sarmento and Descy, 2008;Schlüter et al, 2016). A total of 60 randomized ratio matrices were constructed from the initial ratios for each dataset, and the program was run 60 times.…”

“…Nevertheless, metatranscriptomics alone is not sufficient to determine the taxonomic composition of an active community and demands complementary approaches (Shakya et al, 2019). For phytoplankton communities, the analysis of group-specific accessory pigment patterns provides a fast method that is frequently used to identify phytoplankton functional taxonomic composition (Mackey et al, 1996;Sarmento and Descy, 2008;Schlüter et al, 2016).…”