Dark respiration in the light and in darkness of three marine macroalgal species grown under ambient and elevated CO_2 concentrations

Dark respiration （non-photorespiratory mitochondrial respiration）, which occurs both in the light and in darkness, is vital for growth and survival of algae and plays a critical role in modulating the carbon balance of them. In the present study, we have investigated dark respiration in the light （RL） and in darkness （RD） in three marine macroalgal species, Hizikia fusiformis （phaeophyta）, Gracilaria lemaneiformis （Rhodophyta） and Ulva lactuca （Chlorophyta）, cultured at 20 ℃ using aeration with two CO2 conditions： current ambient （CO2 concentration about 380 μl/L） and elevated CO2 （approximately 720 μl/L） air. RL was estimated by using the Kok method, whereas RD was determined as the rate of O2 influx at zero light. The results showed that both RL and RD were unchanged for the elevated CO2-grown algae relative to ambient CO2 concentration for all the algal species tested. However, RL was significantly lower than RD across all the algal species and growth CO2 treatments, demonstrating that daytime respiration was partly depressed by the light. The percentage of inhibition of respiration by light was similar between ambient and elevated CO2- grown algae. The ratio of respiration to photosynthesis, which tended to decrease when estimated using RL instead of RD, was not altered for the elevated relative to ambient CO2 concentration. The results suggest that RL, rather than RD, is a more accurate estimate of nonphotorespiratory carbon loss in marine macroalgae during the daytime. It would not be anticipated that elevated atmospheric CO2 would exert a substantial influence on respiratory flux either in the light or in darkness in these particular marine macroalgal species.

Impacts of solar UV radiation on grazing, lipids oxidation and survival of Acartia pacif ica Steuer (Copepod)

UV radiation is known to affect aquatic primary producers and their grazers. However, little has been documented on its effects on zooplankton grazing. In this study, the authors investigated the effects of photosynthetically active radiation （PAR, 400–700 nm）, ultraviolet-A （UV-A, 320–400 nm） and ultraviolet-B （UV-B, 280–320 nm） radiation on grazing, mortality and lipids oxidation of the copepod Acartia pacifica collected from the Xiamen Bay. After 30 min of the exposures, the copepod was fed in darkness with the diatom Phaeodactylum tricornutum at two cell concentrations （2.5 × 10 4 and 2.5 × 10 5 cells/ml）. At the low cell concentration, the individuals pre-exposed to PAR （218.0 W/m 2 ）＋UV-A （48.2 W/m 2 ） or PAR＋UV-A＋UV-B （2.1 W/m 2 ） showed suppressed clearance and grazing activities compared with those receiving PAR alone, by 22.7% and 17.1% for clearance and by 22.6% and 5.5% for grazing rates, respectively. However, the suppression on clearance and grazing became indistinctive at the high food concentration. Exposures to UV-A and UV-B led to increased lipid oxidation and higher mortality, furthermore, the mortality linearly increased with enhanced oxidation of lipid.

Satellite remote sensing of ultraviolet irradiance on the ocean surface

Ultraviolet （UV） radiation has a significant influence on marine biological processes and primary productivity; however, the existing ocean color satellite sensors seldom contain UV bands. A look-up table of wavelength- integrated UV irradiance （280-400 nm） on the sea surface is established using the coupled ocean atmosphere radiative transfer （COART） model. On the basis of the look-up table, the distributions of the UV irradiance at middle and low latitudes are inversed by using the satellite-derived atmospheric products from the Aqua satellite, including aerosol optical thickness at 550 nm, ozone content, liquid water path, and the total precipitable water. The validation results show that the mean relative difference of the 10 d rolling averaged UV irradiance between the satellite retrieval and field observations is 8.20% at the time of satellite passing and 13.95% for the daily dose of UV. The monthly-averaged UV irradiance and daily dose of UV retrieved by satellite data show a good correlation with the in situ data, with mean relative differences of 6.87% and 8.43%, respectively. The sensitivity analysis of satellite inputs is conducted. The liquid water path representing the condition of cloud has the highest effect on the retrieval of the UV irradiance, while ozone and aerosol have relatively lesser effect. The influence of the total precipitable water is not significant. On the basis of the satellite-derived UV irradiance on the sea surface, a preliminary simple estimation of ultraviolet radiation＇s effects on the global marine primary productivity is presented, and the results reveal that ultraviolet radiation has a non-negligible effect on the estimation of the marine primary productivity.

微小核糖核酸作为新型生物标志物在HIV-1感染控制中的临床应用

微小核糖核酸(miRNAs),19～24bp的单链非编码RNA序列是信使核糖核酸(mRNA)翻译和转换的关键调节剂,最终导致mRNA翻译抑制或者降解。综述回顾了miRNAs在1型艾滋病病毒(HIV-1)感染与宿主的相互作用过程中所起的调节作用。HIV-1感染导致miRNAs的改变对艾滋病发病机制和疾病进展的影响。重点探讨了miRNAs潜在的临床应用,评估了作为新型生物标志物、参与构建核酸疫苗,进行临床抗病毒治疗等应用方面存在的问题和需要克服的困难。

自噬在人类免疫缺陷病毒和结核分枝杆菌共同感染中的作用

人类免疫缺陷病毒/结核分枝杆菌(HIV/M.tb)共同感染已经成为发展中国家的主要公共卫生威胁。自噬是一种溶酶体分解代谢过程,正常状态下维持细胞内环境的稳态,还涉及细胞内病原体如HIV-1和M.tb的清除,可增强机体的免疫防御能力。本文概述在HIV-1和M.tb单独感染以及共同感染的背景下自噬对机体免疫防御的调控,全面了解病原体与自噬的相互作用,展望未来开发基于自噬原理新的预防性疫苗和治疗干预措施的巨大潜力。

Photosynthetic bicarbonate utilization in Porphyra haitanensis(Bangiales,Rhodophyta)

The activities of carbonic anhydrase (CA) and photosynthesis of Porphyra haitanensis were investigated in order to see its photosynthetic utilization of inorganic carbon source. Both intra- and extra-cellular CA activities existed in the thallus. CA inhibitors, acetazolamide (AZ) and ethoxy-zolamide (EZ), remarkably depressed the photosynthetic oxygen evolution in seawater of pH 8.2 and 10.0, and EZ showed stronger inhibition than AZ. The observed net photosynthetic rate in seawater of pH 8.2 was much higher than that of CO2 supply theoretically derived from spontaneous dehydration of HCO3. P. haitanensis also showed a rather high pH compensation point (9.9). The results demonstrated that P. haitanensis could utilize bicarbonate as the external inorganic carbon source for photosynthesis. The bicarbonateutilization was closely associated with HCO3- dehydrationcatalyzed by extracellular CA activity. The inorganic carbon composition in seawater could well saturate the photosynthesis of P. haitanensis. The

Processes of coastal ecosystem carbon sequestration and approaches for increasing carbon sink

The oceans are the largest carbon pools on Earth, and play the role of a "buffer" in climate change. Blue carbon, the carbon(mainly organic carbon) captured by marine ecosystems, is one of the important mechanisms of marine carbon storage.Blue carbon was initially recognized only in the form of visible coastal plant carbon sequestration. In fact, microorganisms(phytoplankton, bacteria, archaea, viruses, and protozoa), which did not receive much attention in the past, account for more than 90% of the total marine biomass and are the main contributors to blue carbon. Chinese coastal seas, equivalent to 1/3 of China's total land area, have a huge carbon sink potential needing urgently research and development. In this paper, we focus on the processes and mechanisms of coastal ocean's carbon sequestration and the approaches for increasing that sequestration. We discuss the structures of coastal ecosystems, the processes of carbon cycle, and the mechanisms of carbon sequestration. Using the evolution of coastal ocean's carbon sinks in sedimentary records over geologic times, we also discuss the possible effects of natural processes and anthropogenic activities on marine carbon sinks. Finally, we discuss the prospect of using carbon sequestration engineering for increasing coastal ocean's carbon storage capacity.

Enhanced calcification ameliorates the negative effects of UV radiation on photosynthesis in the calcifying phytoplankter Emiliania huxleyi

The calcifying phytoplankton species,coccolithophores,have their calcified coccoliths around the cells,however,their physio-logical roles are still unknown.Here,we hypothesized that the coccoliths may play a certain role in reducing solar UV radiation(UVR,280-400 nm) and protect the cells from being harmed.Cells of Emiliania huxleyi with different thicknesses of the cocco-liths were obtained by culturing them at different levels of dissolved inorganic carbon and their photophysiological responses to UVR were investigated.Although increased dissolved inorganic carbon decreased the specific growth rate,the increased coccolith thickness significantly ameliorated the photoinhibition of PSII photochemical efficiency caused by UVR.Increase by 91%in the coccolith thickness led to 35%increase of the PSII yield and 22%decrease of the photoinhibition of the effective quantum yield(ΦPSII) by UVR.The coccolith cover reduced more UVA(320-400 nm) than UVB(280-315 nm) ,leading to less inhibition per energy at the UV-A band.