A comparison of methods for detection of phosphate limitation in microalgae

This paper presents the results of studies into the use of the emerging techniques of nutrient induced fluorescence transients (NIFTs) and Fourier Transform InfraRed (FTIR) spectroscopy to determine the nutrient status of microalgae. Four species of microalgae were grown under conditions where growth rate was P-limited or P-replete, and NIFT responses and FTIR spectra in response to the re-supply of P (as PO43-) measured. These responses were compared to more conventional measures of algal nutrient status such as P-uptake rates, P quotas and transient effects of PO43- on oxygen exchange. The NIFT technique and FTIR spectroscopy gave results that were consistent with those obtained by the other techniques. Furthermore, we were able to demonstrate NIFT responses in phytoplankton samples taken from Lake Lucerne (total ambient P less than or equal to 0.13 muM) but not from Lake Zurich (total P 0.55 muM). The potential and limitations of the various techniques are discussed.