INFLUENCE OF IRRADIANCE ON THE FATTY ACID COMPOSITION OF PHYTOPLANKTON¹

Abstract

Eight species of marine phytoplankton commonly used in aquaculture were grown under a range of photon flux densities (PEDs) and analyzed for their fatty acid (FA) composition. Fatty and composition changed considerably at different PFDs although no consistent correlation between the relative proportion of a single FA and μ or chl a · cell−1 was apparent. Within an individual species the percentage of certain fatty acids covaried with PFDs, growth rate and/or chl a · cell−1. The light conditions which produced the greatest proportion of the essential fatty acids was species specific. Eicosapentaenoic acid. 20:5ω3 increased from 6.1% to 15.5% of the total fatty acids of Chaetoceros simplex Ostenfield grown at PFDs which decreased from 225 μE · m−2· s−1 to 6 μE · m−2· s−1, respectively. Most species had their greatest proportion of 20: 5ω3 at low levels of irradiance. Conversely, docosahexaenoic acid, 22:6ω3, decreased from 9.7% to 3.6% of the total fatty acids in Pavlova lutheri Droop as PFD decreased. The percentage of 22:6ω3 generally decreased with decreasing irradiances. In all diatoms the percentage of 16:0 was significantly correlated with PFD, and in three of five diatoms, with growth rate (μ). Results suggest that fatty acid composition is a highly dynamic component of cellular physiology, which responds significantly to variation in PFD.

Imaging of Lipids in Microalgae with Coherent Anti-Stokes Raman Scattering Microscopy

“…For instance, nitrogen-limited conditions have repeatedly been shown to promote significant accumulation of neutral lipids for a wide collection of algal strains (Breuer et al, 2012;Griffiths et al, 2012;Erickson and Jimenez, 2013), and elevated PUFA levels have been reported at low light exposure (Thompson et al, 1990). This raises questions on the underlying cellular mechanisms, knowledge that could guide scientists to identify growth conditions and protocols that more efficiently target the intracellular pathways involved in lipid accumulation.…”

“…The intention with the group of algae grown under LL conditions was to include a study object with elevated PUFA levels. This was done partly based on the research by Thompson et al (1990), where most of the eight marine phytoplankton species investigated, including P. tricornutum, had their greatest proportion of EPA at low levels of irradiance. Despite previous findings, our GC-MS analyses could not discern any increase in EPA (all approximately 20 mg g 21 ) or in DHA (all approximately 1.5 mg g 21 ) at harvest of P. tricornutum grown under LL conditions compared with the Ctrl and NS categories (Table I).…”

“…Under conditions of nitrogen starvation, P. tricornutum accumulates larger amounts of fatty acids, albeit of the more saturated nature (Yongmanitchai and Ward, 1991). However, in response to low irradiance, P. tricornutum has been reported to increase its content of PUFAs, especially EPA (Thompson et al, 1990). In order to optimize strain selection and algal cultivation conditions in relation to lipid accumulation/ lipid profile, accurate tools to quantify total lipids as well as the degree of unsaturation are required.…”

Carbon and nitrogen cycling on intertidal mudflats of a temperate Australian estuary. III. Sources of organic matter

“…Using these methods to estimate the relative importance of algal classes requires an estimate to be made of the ratios of pigments and fatty acids to a measure of biomass such as chlorophyll a (chl a). These may not necessarily be accurate, as the ratios of pigments and fatty acids can change, depending upon environmental conditions (Thompson et al 1990, Porra et al 1997). …”

Potentiality of benthic dinoflagellate cultures and screening of their bioactivities in Jeju Island, Korea

“…The growth rates of dinoflagellates rarely double one per day (Thomas and Carr, 1985). Most of other economically important microalgae species have shown growth rates much higher than 1.0 d ) (Thompson et al, 1990). Different chemicals have been experimented for maximizing the biomass production and CO 2 bio-fixation of microalgae (Nayak et al, 2013).…”