Assessing Impacts of Nutrient Competition on the Chemical Composition of Individual Microalgae Species

Abstract

Microalgae cells can chemically adapt to ambient conditions. In this study, it has been hypothesized that the microalgal species composition could include the mechanism thought to cause changes in the cell content. An FTIR-spectroscopic measurement technique has been developed in this study for investigations of this hypothesis. Experiments were based on culturing microalgae species individually followed by comparing their spectroscopic signatures to the same species cultured under the same ambient conditions in mixtures. While keeping all other parameters the same, any significant spectroscopic shifts between the single-species cultures and the mixed cultures were then attributed to competition effects. These spectroscopic analyses were performed on Dunaliella salina, Dunaliella parva, and Nannochlorpsis oculata. These cells were exposed to concentration series of bicarbonate (C-source), ammonium (N-source), and nitrate (an alternative N-source). It has been shown that there are significant chemical shifts when species are cultured together versus individually, but it was also observed that adaptations of the cells’ chemical composition are not random. In this study, it has also been investigated whether there are species and nutrient independent patterns in such competition processes or whether these effects are purely species and nutrient type dependent. Examples for both scenarios are given but the main focus of this study was to demonstrate that such competition-driven effects on the biomass exist and that they are significant enough to require consideration in chemical analyses of microalgae.

Supplementary materials are available for this article. Go to the publisher's online edition of Analytical Letters to view the supplemental files.

Keywords:

• Chemical composition of biomass
• FTIR spectroscopy
• Inorganic nutrients
• Microalgae cells
• Nutrient competition

Acknowledgments

This article contains supplementary material that can be accessed online.

This work was supported by the National Science Foundation under CHE-1058695 and CHE-1112269.

Notes

Note: These situations are determined at every wavenumber position separately by t-testing the mean absorbance values (absorb.) of singly-grown species #1 (Nannochloropsis oculata in Figure 1) and (Dunaliella parva in Figure 1) to a mixed culture (= mix) of the same species cultured together under the same nutrient conditions.

Note: Fields containing “n/a” involve an empty situation plane which did not yield a correlation coefficient.

Note: Fields containing “n/a” involve an empty situation plane which did not yield a correlation coefficient.