EFFECT OF NUTRIENT AVAILABILITY ON THE BIOCHEMICAL AND ELEMENTAL STOICHIOMETRY IN THE FRESHWATER DIATOM STEPHANODISCUS MINUTULUS (BACILLARIOPHYCEAE)*

Abstract

The objective of this study was to examine the differences in the biochemical and elemental stoichiometry of a freshwater centric diatom, Stephanodiscus minutulus (Grun.), under various nutrient regimes. Stephanodiscus minutulus was grown at μ or 22% of μ under limitation by silicon, nitrogen, or phosphorus. Cell sizes for nutrient-limited cultures were significantly smaller than the non-limited cell sizes, with N-limited cells being significantly smaller than all other treatments. Compared with the nutrient-replete treatment, both carbohydrates and lipids increased in Si- and P-limited cells, whereas carbohydrates increased but proteins decreased in N-limited cells. All of the growth-limited cells showed an increase of carbohydrate and triglyceride, and a decrease of cell size and polar lipids as a percentage of total lipids. The non-limited cells also had a significantly higher chl a concentration and galactolipids as a percentage of total lipids than any of the limited treatments, and the low-Si and low-P cells had significantly higher values than the low-N cells. The particulate C concentrations showed significant differences between treatments, with the Si- and P-limited treatments being significantly higher than the N- and non-limited treatments. Particulate Si did not show a strong relationship with any of the parameters measured, and it was the only parameter with no differences between treatments. The low-Si cells had a significantly higher P content (about two times more) than any other treatment, presumably owing to the luxury consumption of P, and a correspondingly high phospholipid concentration. The elemental data showed that S. minutulus had a high P demand with low optimum N:P (4) and Si:P (10) ratios and a C:N:P ratio of 109:16:2.3. The particulate C showed a positive relationship with POM (r = 0.93), dry weight (r = 0.88), lipid (r = 0.87) and protein (r = 0.84, all P < 0.0001). Particulate N showed a positive relationship with galactolipids (r = 0.95), protein (r = 0.90), dry weight (r = 0.78), lipid (r = 0.75), and cell volume (r = 0.64, all P < 0.0001). It is evident that nutrient limitation in the freshwater diatom S. minutulus has pronounced effects on its biochemical and elemental stoichiometry.

Impact of phosphorus quota and growth phase on carbon allocation inChlamydomonas reinhardtii: an FTIR microspectroscopy study

“…Each spectrum is a mean of 10 replicate spectra, each collected over a randomly selected 10 Â 10 mm area of continuous cellular monolayer. The increased synthesis of carbohydrates and lipids seen in this study reflect those seen under P-deficiency in other algae, including the green alga Ankistrodesmus (Kilham et al, 1997) and the diatom Stephanodiscus (Lynn et al, 2000). Changes in carbon allocation during exponential phase suggest that increases in cellular storage products, particularly carbohydrate, occurred when the cells were still undergoing division.…”

Effect of nutrients on total lipid content and fatty acids profile of Scenedesmus obliquus

“…The fatty acids content as well as the ratio between unsaturated and saturated fatty acids is an important parameter for determination of algae value. SFAs were found to increase by increasing the iron amount in Nannochloropsis oculata 20 . In Dunaliella tertiolecta and Stephanodiscus minutulus, changes of the SFA's values were directly related to changes in the amount of nitrogen 24 .In the present study, SFAs showed significantly positive correlationship with manganese and iron first of all, then sodium which were sufficiently present in Trenkenshu medium (Table 3 and Figure 5).…”

“…The quantity and quality of fatty acids content as well as the entire biochemical composition varies in response to environmental conditions 8,20,24,25,38,39 . Particularly, under unfavorable environmental or stress conditions for growth, such as salinity, temperature, pH, and nutrient levels, many algae alter their lipid biosynthetic pathways towards the formation and accumulation of neutral lipids to control intracellular stress 13,40 .…”

“…Scenedesmus Meyen is a freshwater and marine genus with 433 known species worldwide 17 , of which 27 species has been reported in aquatic ecosystems of Iran 18 . In nature, the cytoplasmic oil droplets are accumulated under stressful environmental conditions, such as high temperature, light intensity and rise in salinity [19][20][21][22] . In culture, nutritional composition of the medium has more effects on the total lipid content and fatty acid profile, among which nitrogen, silicon and phosphorus have greater roles [20][21][22][23][24] , followed by iron [25][26][27][28] .…”

“…In nature, the cytoplasmic oil droplets are accumulated under stressful environmental conditions, such as high temperature, light intensity and rise in salinity [19][20][21][22] . In culture, nutritional composition of the medium has more effects on the total lipid content and fatty acid profile, among which nitrogen, silicon and phosphorus have greater roles [20][21][22][23][24] , followed by iron [25][26][27][28] . In 1987, the lipid content and fatty acid composition of Scenedesmus obliquus was determined 29 , but at a later time, the values differed within the species [30][31][32] .…”