On the effect of Fe(Ⅲ) on proliferation of Microcystis aeruginosa at high nitrate and low chlorophyll condition

The impact of Fe concentrations on the growth of Microcystis aeruginosa in aquatic systems under high nitrate and low chlorophyll conditions was studied. The responses of cell density,total and cell chlorophyll-a intracellular Fe content and organic elemental composition of M.aeruginosa to different concentration gradients of Fe（Ⅲ） in the solutions were analysed. The results showed that the proliferation speeds of M. aeruginosa were：（1） decelerated when the Fe（Ⅲ） concentration was lower than 50 μg/L in the solutions,（2） promoted and positively related to the increase of Fe（Ⅲ） concentration from 100 to 500 μg/L in the solutions over the experimental period, and（3） promoted in the early stage but decelerated in later stages by excess adsorption of Fe by cells when the Fe（Ⅲ） concentration was higher than 500 μg/L in the solutions. The maximum cell density, total and cell chlorophyll-a were all observed at 500 μg Fe（Ⅲ）/L concentration. The organic elemental composition of M. aeruginosa was also affected by the concentration of Fe（Ⅲ） in the solutions, and the molecular formula of M. aeruginosa should be expressed as C7–7.5H14O0.8–1.3N3.5–5according to the functions for different Fe（Ⅲ）concentrations. Cell carbon and oxygen content appeared to increase slightly, while cell nitrogen content appeared to decrease as Fe（Ⅲ） concentrations increased from 100 to 500 μg/L in the solutions. This was attributed to the competition of photosynthesis and nitrogen adsorption under varying cell Fe content.

Effect of Low Content Chlorophyll on Distribution Properties of Absorbed Light Energy in Leaves of Mutant Rice

This paper reported the diurnal variations of photochemical efficiency of PSII, thermaldissipation rate and other physiology process in the low content chlorophyll mutant rice andits wild type under field conditions, and analyzed the difference of absorbed light distributionbetween the two rice varieties in a day. The results showed that the mutant had poor absorbedlight because of its little light absorption coefficient, but higher electron transportg ratecould partly reduce the disadvantageous effect of deficient absorbed light in mutant. Comparedwith wild-type rice, the mutant had less excess excitation energy and the fraction of absorbedlight allocated to photochemical process was more.

Microalgae Improve the Photosynthetic Performance of Rice Seedlings(Oryza sativa L.)under Physiological Conditions and Cadmium Stress

The aim of this study was to assess the impact of the microalgae Chlorella vulgaris on the rice seedlings at physiological conditions and under cadmium(Cd)stress.We examined the effects of C.vulgaris in the nutrient solution on rice seedlings grown hydroponically in the presence and the absence of 150μM CdCl2,using the low(77 K)temperature and pulse amplitude modulated(PAM)chlorophyll fluorescence,P700 photooxidation measurements,photochemical activities of both photosystems,kinetic parameters of oxygen evolution,oxidative stress markers(MDA,H_(2)O_(2) and proline),pigment content,growth parameters and Cd accumulation.Data revealed that the application C.vulgaris not only stimulates growth and improves the functions of photosynthetic apparatus under physiological conditions,but also reduces the toxic effect of Cd on rice seedlings.Furthermore,the presence of the green microalgae in the nutrient solution of the rice seedlings during Cd exposure,signifi-cantly improved the growth,photochemical activities of both photosystems,the kinetic parameters of the oxygen-evolving reactions,pigment content and decreased lipid peroxidation,H_(2)O_(2) and proline content.Data showed that the alleviation of Cd-induced effects in rice seedlings is a result of the Cd sorption by microalgae,as well as the reduced Cd accumulation in the roots and its translocation from the roots to the shoots.

Trophic gauntlet effects on fisheries recovery:a case study in Sansha Bay,China

Low biological productivity causes ecosystem energy deficiency.Sansha Bay is an important spawning and nursery ground for migratory fish in the East China Sea(ECS).There is significant mariculture in this area,but stock enhancement programs and seasonal fishery closures have failed to recover populations of the commercially important species,Larimichthys crocea.We want to figure out the potential reason of unsuccessful L.crocea resource in recent 30 years.In this study,the trophic status of L.crocea,the food source proportions of L.crocea and zooplankton,and the food web structure and functioning of Sansha Bay was analyzed.A high nutrient low chlorophyll phenomenon was observed:this prevented harmful algal blooms,and phytoplankton growth was restrained by intensive macroalgal culture,resulting in a low abundance of zooplankton in Sansha Bay.Phytoplankton was the most important food source of zooplankton,and zooplankton was the greatest food source of juvenile L.crocea.Analyzed L.crocea suffered from starvation.Crucially,most of the phytoplankton was not used efficiently in the Sansha Bay ecosystem.This study suggests that trophic bottleneck,caused by food limitation,is a potential reason for unsuccessful fishery recovery in enclosed bay with macroalgal culture.