Photoinhibition and β-Carotene Production From Dunaliella sp. Isolated From Salt Pans of Goa

Abstract The microalgae Dunaliella is a commercially viable species and well known for its extreme environmental tolerance and β-carotene production under stressful conditions. We examined the effect of salinity and light intensity on the growth and β-carotene production, respectively, in two different species of Dunaliella: Dunaliella. sp. and D. salina, isolated from the salt pans of Goa. Both the species were cultured in growth media with different salinity levels to establish the optimum salinity favouring maximum cell growth. Thereafter, the cells were cultured under optimum NaCl concentration, exposed to a range of light intensity and monitored for β-carotene production. The two species, identified based on their molecular characteristics, displayed a significant difference in growth and β-carotene production. Both D. salina and D. sp achieved a maximum cell density of 11.82×106 cells/ml and 18.76×106 cells/ml at 0.75 M and 0.5 M salinity, respectively. D. salina accumulated a large amount of total carotenoid (36.95 pg. cell-1) when cultured at 0.75 M salinity and exposed to high light intensity (1000 µmol m− 2 S− 1). In contrast, the carotenoid content per cell was low in Dunaliella sp. (3.07 pg. cell-1) when cultured under optimal salinity (0.5M) and high light intensity, indicating photoinhibition. We found that different Dunaliella species exhibit different photo-physiological properties that need further evaluation to identify the right candidate for industrial applications.

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Light intensity regulates phototaxis, foraging and righting behaviors of the sea urchin Strongylocentrotus intermedius

PeerJ ◽

10.7717/peerj.8001 ◽

2019 ◽

Vol 7 ◽

pp. e8001 ◽

Cited By ~ 4

Author(s):

Jiangnan Sun ◽

Xiaomei Chi ◽

Mingfang Yang ◽

Jingyun Ding ◽

Dongtao Shi ◽

...

Keyword(s):

Light Intensity ◽

Foraging Behavior ◽

Sea Urchins ◽

High Light Intensity ◽

High Light ◽

Strongylocentrotus Intermedius ◽

Low Light ◽

Low Light Intensity ◽

Light Intensities ◽

Significant Difference

Small sea urchins Strongylocentrotus intermedius (1–2 cm of test diameter) are exposed to different environments of light intensities after being reseeded to the sea bottom. With little information available about the behavioral responses of S. intermedius to different light intensities in the environment, we carried out an investigation on how S. intermedius is affected by three light intensity environments in terms of phototaxis, foraging and righting behaviors. They were no light (zero lx), low light intensity (24–209 lx) and high light intensity (252–2,280 lx). Light intensity had obvious different effects on phototaxis. In low light intensity, sea urchins moved more and spent significantly more time at the higher intensity (69–209 lx) (P = 0.046). S. intermedius in high light intensity, in contrast, spent significantly more time at lower intensity (252–690 lx) (P = 0.005). Unexpectedly, no significant difference of movement (average velocity and total distance covered) was found among the three light intensities (P > 0.05). Foraging behavior of S. intermedius was significantly different among the light intensities. In the no light environment, only three of ten S. intermedius found food within 7 min. In low light intensity, nine of 10 sea urchins showed successful foraging behavior to the food placed at 209 lx, which was significantly higher than the ratio of the number (two of 10) when food was placed at 24 lx (P = 0.005). In the high light intensity, in contrast, significantly less sea urchins (three of 10) found food placed at the higher light intensity (2,280 lx) compared with the lower light intensity (252 lx) (10/10, P = 0.003). Furthermore, S. intermedius showed significantly longer righting response time in the high light intensity compared with both no light (P = 0.001) and low light intensity (P = 0.031). No significant difference was found in righting behavior between no light and low light intensity (P = 0.892). The present study indicates that light intensity significantly affects phototaxis, foraging and righting behaviors of S. intermedius and that ~200 lx might be the appropriate light intensity for reseeding small S. intermedius.

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Effects of alkalinity and salinity at low and high light intensity on hydrogen isotope fractionation of long-chain alkenones produced by <i>Emiliania huxleyi</i>

10.5194/bg-2017-311 ◽

2017 ◽

Author(s):

Gabriella M. Weiss ◽

Eva Y. Pfannerstill ◽

Stefan Schouten ◽

Jaap S. Sinninghe Damsté ◽

Marcel T. J. van der Meer

Keyword(s):

Light Intensity ◽

Environmental Conditions ◽

Hydrogen Isotope ◽

Isotope Fractionation ◽

Emiliania Huxleyi ◽

High Light Intensity ◽

High Light ◽

Sea Surface Salinity ◽

Significant Difference ◽

Long Chain

Abstract. Over the last decade, hydrogen isotope fractionation of long-chain alkenones have been shown to be a promising proxy for reconstructing paleo sea surface salinity due to a strong hydrogen isotope fractionation response to salinity across different environmental conditions. However, to date, the decoupling of the effects of alkalinity and salinity, parameters that co-vary in the surface ocean, on hydrogen isotope fractionation of alkenones has not been assessed. Furthermore, as the alkenone-producing haptophyte, Emiliania huxleyi, is known to grow in large blooms under high light intensities, the effect of salinity on hydrogen isotope fractionation under these high irradiances is important to constrain before using hydrogen isotope fractionation to reconstruct paleosalinity. Batch cultures of the marine haptophyte E. huxleyi strain CCMP 1516 were grown to investigate the hydrogen isotope fractionation response to salinity at high light intensity and independently assess the effects of salinity and alkalinity. Our results suggest that alkalinity does not significantly influence hydrogen isotope fractionation of alkenones, but salinity does have a strong effect. Additionally, no significant difference was observed between the fractionation responses to salinity recorded in alkenones grown under both high and low light conditions. Comparison with previous studies suggests that the fractionation response to salinity in culture is similar under different environmental conditions, strengthening the applicability of hydrogen isotope fractionation as a paleosalinity proxy.

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