Photosynthetic efficiency, cell volume, and elemental stoichiometric ratios in Thalassirosira weissflogii under phosphorus limitation

• Published in: Chinese journal of oceanology and limnology Vol. 29; no. 5; pp. 1048 - 1056
• Main Author: 刘胜 郭志灵 李涛 黄晖 林森杰
• Format: Journal Article
• Language: English
• Published: Heidelberg SP Science Press 01.09.2011; Springer Nature B.V
• Subjects: Algae; Aquatic ecosystems; Availability; Biology; Cell culture; Cell division; Cell size; Chlorophyll; Chlorophylls; Cultures; Depletion; Earth and Environmental Science; Earth Sciences; Fucoxanthin; Marine; Marine biology; Metabolism; Nutrients; Oceanography; Phosphates; Phosphorus; Photosynthesis; Phytoplankton; Plankton; Stoichiometry; Thalassiosira weissflogii; 元素; 光合效率; 化学计量比; 叶绿素a; 溶解无机磷; 相对稳定; 细胞体积; 营养限制; physiological responses; diatom; PAM; elemental ratio; phosphorus
• ISSN: 0254-4059; 2096-5508; 1993-5005; 2523-3521
• DOI: 10.1007/s00343-011-0224-2

Nutrient limitation is known to inhibit growth and metabolism and to alter elemental stoichiometric ratios in phytoplankton. In this study, physiological changes in Thalassirosira weissflogii were measured under different dissolved inorganic phosphate （DIP） regimes in semi-continuous cultures to revisit the utility of the Redfield ratio for assessing nutrient limitation. The results showed that cell size increased with decreasing DIP availability. In the P-depleted treatment （f/2-P） the cell size was 1.48 times larger than that in the P-limited （f/100） treatment and 2.67 times larger than that in the P-saturated treatment （f/2 and f/10）. The fucoxanthin to chlorophyll a ratio （Fuco/chl a） was relatively stable （about 0.3） in P-saturated cultures and was 10 times higher than that in P-limited and P-depleted cultures. During the experimental period, the photosynthetic efficiency index,ΔF/Fm＇, was relatively stable at -0.50 in the P-saturated cultures, but quickly declined with decreasing DIP availability. Although cellular P content showed a significant difference between the P-saturated culture （1.6 pg/cell） and the P-limited culture （0.7 pg/cell）, the N/P ratio in T. weissflogii did not show a trend with DIP availability and fluctuated slightly around 25. Our results suggest that cell division in T. weissflogii is not strictly size-gated but is probably regulated by a biochemical, and hence, an elemental stoichiometric ratio threshold, and that deviation of the cellular N/P ratio from the Redfield ratio is not a reliable indicator of algal nutrient stress.