Strict stoichiometric homeostasis of Cryptomonas pyrenoidifera (Cryptophyceae) in relation to N:P supply ratios

Abstract

A common freshwater cryptophyte, Cryptomonas pyrenoidifera, was cultivated in batch-cultures to analyze intraspecific variation in elemental stoichiometry along a broad gradient of pulsed phosphorus (P) enrichment during the early acclimation period and to determine the immediate homeostatic capacity of the nitrogen-to-phosphorus (N:P) ratio of this alga when nutrients are at saturating levels. Experimental results revealed that nitrogen (N) and P cell quotas significantly increased with increasing P concentration. However, despite the wide range of N:P ratios in the medium, C. pyrenoidifera N:P ratios were highly stable at higher P-level treatments, indicating a highly conservative behavior and suggesting strict elemental homeostasis when nutrients are at saturating levels. The strictly homeostatic N:P ratio appears to be attributable to their high potential for a fast luxury consumption of both N and P after a brief and intense episode of increased resource availability and to physiological limits on their nutrient storage capacity. Most importantly, the N:P biomass ratio at nutrient saturating levels converged around 11:1, which was the observed ratio of maximum internal cell quotas for N and P (i.e., Q max , N :Q max , P ) under the prevailing experimental conditions. This value is particularly informative for C. pyrenoidifera because it represents cell storage quotients and may be a taxon-specific evolutionary optimum, providing a reference point to infer the grade of nutrient-limitation. The experimental data give ranges of variation in C. pyrenoidifera elemental composition permitting, among others, proper parameterization of cryptophyte stoichiometry models.

Fluorescence Excitation Spectroscopy for Phytoplankton Species Classification Using an All-Pairs Method: Characterization of a System with Unexpectedly Low Rank

“…Jeffrey and Vesk provide a breakdown of the types of pigments by class that characterize 13 different broad classes of phytoplankton distinguishable by pigments. 38 Of the 13 classes—Prochlorophyta, Cyanophyta, Rhodophyta, Cryptophyta, Chlorophyceae, Prasinophyceae, Euglenophyta, Eustigmatophyta, Bacillariophyta, Dinophyta, Prymnesiophyceae, Chrysophyceae, and Raphidophyceae—this study included representatives of six: Dinophyta (dinoflagellates, five species), Bacillariophyceae (diatoms, six species), Cryptophyta (cryptophytes, 14 species), Raphidophyceae (raphidophytes, one species), Prymnesiophyceae (haptophytes, two species), and Chlorophyceae (chlorophytes, two species). Although we do not have examples of all the broader classes, we have multiple examples of some and can consider how well they group together.…”

“…One source lists 47 distinct pigments that could contribute to the fluorescence excitation spectra of phytoplankton. 38 Those 47 pigments could have more than 47 different absorption spectra due to packaging and saturation effects (vide supra). Only 31 species were studied in this work, so we could easily justify an observed data rank approaching 31.…”

“…It might be that most of the 47 known pigments are minor contributors to the fluorescence excitation spectrum; or that many pigments co-vary. For instance, Jeffrey and Vesk 38 reveal that a much smaller subset of those 47 pigments can be used to effectively discriminate between most groups of phytoplankton. Alternatively, there might be great spectroscopic similarity among many structurally different pigments.…”

“…Third, its shape is spherical under an optical microscope, very different from the shape described by Hill and others who report it. 36,37 Fourth, there are other cultures of the same species with synonymous names that are in our current collection and that contain the correct pigments and have the correct morphology and that appear nearby C. ovata in the figure (not shown). Fifth, DNA analysis using cryptophyte primers failed.…”

Seasonal Water Level Fluctuation and Concomitant Change of Nutrients Shift Microeukaryotic Communities in a Shallow Lake

“…In the wet season, module B, C, and E were dominated by Chlorophyta (Figures 3 and 8), which could be strongly driven by high temperature, high light, and high organic matter [43,92]. Like the overall microeukaryotic communities, most major modules in the dry season were closely correlated with nutrients, for example, high concentration of available nitrogen and SRP driven the growth of Cryptomonas and Ciliophora [33,93,94]. However, in the wet season, most major modules only had weak or no correlations with nutrients.…”