Effects of Lanthanum on the Photosystem II Energy Fluxes and Antioxidant System of Chlorella Vulgaris and Phaeodactylum Tricornutum

Abstract

The rare earth elements are widely used in agricultural and light industry development. They promote the growth of crop seedlings, enhance root development and change the metal properties. Due to the large amount of rare earth minerals mined in China, rare earth elements have been detected in both coastal and estuary areas. They cause pollution and threaten the health of aquatic organisms and human beings. This study investigates the effects of lanthanum on two marine bait algae, and analyzes the changes in the photosynthetic and antioxidant systems of the two algae. The results show that rare earth elements have significant inhibitory effects upon the two algae. The OJIP kinetic curve value decreases with an increasing concentration of La(NO3)3 ·6H2O. The parameters of the fluorescence value were analyzed. The ABS/RC increases and the DI0/RC decreases during the first 24 h after exposure. The effects on the photosynthetic and antioxidant systems at low concentrations (both EC10 and EC20) show that the TR0/ABS increases, and the ET0/RC, ABS/RC, and DI0/RC has a decreasing trend after 30 min. However, after 24 h, normal levels were restored. In addition, the study finds that the TR0/ABS increases after 24 h, leading to an increase in reactive oxygen species. The antioxidant system analysis also confirms the increase in the activities of antioxidant enzymes, such as SOD and GSH. The experiment is expected to support the marine pollution of rare earths and the theoretical data of the impact on marine primary producers.

A first attempt to evaluate the toxicity to Phaeodactylum tricornutum Bohlin exposed to rare earth elements

“…To the best of our knowledge, this is the first study reporting a large set of REEs toxicity data towards P. tricornutum. Previous data are available only from Sun et al (2019) on La but considering only nominal concentrations. The EC 50 of La from this study (2.46 mg/L) is more than 4 times lower than that obtained by (Sun et al, 2019) (10.08 mg/L), being such difference attributable to the use in our paper of measured concentrations.…”

Lanthanum Prolongs Vase Life of Cut Tulip Flowers by Increasing Water Consumption and Concentrations of Sugars, Proteins and Chlorophylls

“…In rice, the application of appropriate concentrations of La decreased the level of ROS, and hormetic effects on the antioxidant metabolism were also evident 56 . Likewise, in www.nature.com/scientificreports www.nature.com/scientificreports/ two marine bait algae (Chlorella vulgaris and Phaeodactylum tricornutum), the application of La(NO 3 ) 3 × 6H 2 O increased the activities of antioxidant enzymes, such as SOD and GSH 57 . Therefore, hormetic effects of La stimulating the antioxidant system can be observed in both higher and lower plants, and these effects may be responsible, at least in part, for the preservation capacity of La in cut flowers during postharvest.…”

Effects of Phenolic Pollution on Interspecific Competition between Microcystis aeruginosa and Chlorella pyrenoidosa and their Photosynthetic Responses

“…Firstly, 2 mL of algal cells were kept in the dark for 15 min. Then a series of chlorophyll-a fluorescence parameters and the induction curves were recorded by a FluorPen fluorometer (AquaPen C100, Photon Systems Instruments, Czech) at room temperature [23,24,25]. This fluorometer was equipped with two types of excitation wavelength at 455 nm and 620 nm.…”

“…The OJIP test (Fluorescence response curves detection) was conducted to analyze the changes in these fluorescent parameters, which can provide adequate information about the structure, conformation, and the function of photosynthetic apparatus. From the OJIP transient, the measured parameters ( F 0 , F m , F 300μs , F J , F I and so on) were used to calculate new parameters, which are displayed in Table 1 [24,25].…”