ALBERT

Description: A mesocosm experiment was conducted in Wuyuan Bay (Xiamen), China, to investigate the effects of elevated pCO2 on bloom formation by phytoplankton species previously studied in laboratory-based ocean acidification experiments, to determine if the indoor-grown species performed similarly in mesocosms under more realistic environmental conditions. We measured biomass, primary productivity and particulate organic carbon (POC) as well as particulate organic nitrogen (PON). Phaeodactylum tricornutum outcompeted Thalassiosira weissflogii and Emiliania huxleyi, comprising more than 99% of the final biomass. Mainly through a capacity to tolerate nutrient-limited situations, P. tricornutum showed a powerful sustained presence during the plateau phase of growth. Significant differences between high and low CO2 treatments were found in cell concentration, cumulative primary productivity and POC in the plateau phase but not during the exponential phase of growth. Compared to the low pCO2 (LC) treatment, POC increased by 45.8–101.9% in the high pCO2 (HC) treated cells during the bloom period. Furthermore, respiratory carbon losses of gross primary productivity were found to comprise 39–64% for the LC and 31–41% for the HC mesocosms (daytime C fixation) in phase II. Our results suggest that the duration and characteristics of a diatom bloom can be affected by elevated pCO2. Effects of elevated pCO2 observed in the laboratory cannot be reliably extrapolated to large scale mesocosms with multiple influencing factors, especially during intense algal blooms.

Description: Increasing CO2 levels in the surface water of oceans are expected to decrease oceanic pH and lead to seawater acidification. The responses of macroalgaea to this acidification of coastal waters have been studied in detail; however, most reports have focused on the adult stage only, while ignoring other life cycle stages. In this study, the economically important seaweed species Pyropia yezoensis was cultured under two CO2 concentrations (ambient CO2: 400 μatm; elevated CO2: 1000 μatm) and two light intensities (low light intensity: 80 μmol photons/m**2 /s; and high light intensity: 240 μmol photons/m**2 /s). The effects on the growth and photosynthetic performance of P. yezoensis were explored at different life cycle stages. Relative growth rates were significantly elevated at the conchocelis stage under high light intensity and elevated CO2 concentration. Moreover, the Pmax of P. yezoensis was also increased under high light intensity. However, this positive effect inversed at the thallus stage. The relative growth rate, relative electron transport rate (rETR), and net photosynthetic rate decreased at the thallus stage in response to high CO2 concentration. Under low light intensity, elevated CO2 concentration significantly increased the relative growth rates of conchocelis and thallus stages. These were 269% and 45% higher at elevated CO2 concentration compared with ambient CO2 concentrations, respectively. The Chl a and phycoerythrin levels were also higher under elevated CO2 level at the conchocelis stage. However, the rETR for the thallus stage was elevated under low light. This suggests that seawater acidification could positively affect algae at low light conditions (especially at the conchocelis stage). Different growth stages of P. yezoensis may respond differently to seawater acidification and changes of light intensity. Thalli growth stage, stocking density, and seawater depth should be considered in different areas to optimize the primary production of macroalgae.

Description: The purpose of this study was to investigate the effects of ocean acidification and nutrient level on the growth and photosynthetic performance of the diatom Thalassiosira (Conticribra) weissflogii. Cells were exposed to varying levels of CO2 [current CO2 (LC), 400 μatm; high CO2 (HC), 1000 μatm] and nutrients, with NO3− and PO43− concentrations enriched, respectively, at 50 μmol/l and 5 μmol/l [high nutrient (HN)], 20 μmol/l and 2 μmol/l [mid-level nutrient (MN)] and 10 μmol/l and 1 μmol/l [low nutrient (LN)]. After acclimatization for over 20 generations, no significant differences in growth rates were observed between LC and HC cultures under both HN and LN conditions; whereas, HC significantly reduced the growth rate under MN conditions. Lower nutrient loading significantly inhibited the growth rates of both LC and HC cultures; whereas, HC (but not LC) significantly decreased chlorophyll a and carotenoid contents in LN treatments. HC conditions significantly increased maximum relative electron transport rates (rETRmax) and saturating light intensity (Ik) of HN cultures, with rETRmax showing a positive relationship with growth rates stimulated by nutrient enrichments. The maximum (Fv/Fm) and effective quantum yield (Yield) were all inhibited under LN conditions, with the greatest reduction in Yield observed under LC conditions, corresponding to the highest nonphotochemical quenching, lowest light use efficiency (α) and lowest rETRmax. Based on these results, ocean acidification and nutrient availability may influence photosynthetic performance in T. weissflogii individually or interactively, with the future growth of marine diatoms mediated by these codependent environmental drivers.

Description: Ultrafine particles with a diameter below 1 μm are strongly linked to traffic and industrial emissions, causing a growing global health concern. In order to reveal the characteristics of ultrafine particles in central China, which makes up the sparse research in industrial cities of a developing country, particle number concentrations (PNC) together with meteorological parameters and concentrations of trace gases were measured over one year in Wuhan. The number concentration of ultrafine particles peaked in winter and was the lowest in summer across the entire size range monitored. Further, particles with a diameter smaller than 30 nm increased dramatically in concentration with decreasing diameter. The monthly averaged number concentrations of particles discriminated in three size ranges formed a near- inverse parabolic distribution peaking in January. This trend is supported by a negative correlation between PNC and precipitation, temperature, and mixing layer height, which emphasizes the effect of these meteorological parameters on scouring, convection, and diffusion of particles. However, since wind not only disperses particulate matter but also brings in exogenous particles, wind speed plays an equivocal role in particle number concentrations. The diurnal analysis indicates that hourly measurements of trace gases concentrations could be used as a proxy for dense industrial activities and to reveal some complex chemical reactions. The results of this study offer reasonable estimations of particle impacts and provide references for policymaking of emission control in the industrial cities of developing countries.

Description: The Flash Disk worms, spreading via both Web-based scanning and removable devices between multiple subnets, have become a serious threat to the Internet, especially those physically isolated subnets. We present a model which incorporates specific features of these worms in this paper. Then, we analyze the dynamic behaviors of the model when one subnet is considered. Analytical result shows that the Flash Disk worm can self-perpetuate when and will die out otherwise. When multiple subnets are considered, we get that once a computer is infected by the Flash Disk worms, other computers in that subnet will be infected in a short time. Thus, for any subnet, to contain the Flash Disk worms, the most effective way is to prevent the first infected individual by improving the users’ security awareness of using removed devices. Our results are illustrated by numerical simulation.

Description: Utilizing the data from the magnetometer instrument which is a part of the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument suite onboard the Van Allen Probe A from Sep. 2012 to Apr. 2014, when the apogee of the satellite has passed all the MLT sectors, we obtain the statistical distribution characteristic of EMIC waves in the inner magnetosphere over all local times from L =3 to L =6. Compared with the previous statistical results about EMIC waves, the occurrence rates of EMIC waves distribute relatively uniform in the MLT sectors in lower L -shells. On the other hand, in higher L -shells, there are indeed some peaks of the occurrence rate for the EMIC waves, especially in the noon, dusk and night sectors. EMIC waves appear at lower L -shells in the dawn sector than in other sectors. In the lower L -shells ( L 〈4), the occurrence rates of EMIC waves are significant in the dawn sector. This phenomenon may result from the distribution characteristic of the plasmasphere. The location of the plasmapause is usually lower in the dawn sector than that in other sectors, and the plasmapause is considered to be the favored region for the generation of EMIC waves. In higher L -shells ( L 〉4) the occurrence rates of EMIC waves are most significant in the dusk sector, implying the important role of the plasmapause or plasmaspheric plume in generating EMIC waves. We have also investigated the distribution characteristics of the hydrogen band and the helium band EMIC waves. Surprisingly, in the inner magnetosphere, the hydrogen band EMIC waves occur more frequently than the helium band EMIC waves. Both them have peaks of occurrence rate in noon, dusk and night sectors, and the hydrogen band EMIC waves have more obvious peaks than the helium band EMIC waves in the night sector, while the helium band EMIC waves are more concentrated than the hydrogen band EMIC waves in the dusk sector. Both them occur significantly in the noon sector, which implies the important role of the solar wind dynamic pressure.

Description: In the alpine meadows of the Qinghai‐Tibetan Plateau, the flowering time of most species was delayed by grazing, but the fruiting time of most species remained stable. Fruiting time was negatively related to the ratio of leaf N content to leaf P content. Grazing exclusion led to the greatest divergence of phenological stages across species, which possibly creates potential reproductive gaps. Abstract Questions The impact of grazing on the phenology of alpine plants has not been deeply explored. In particular, how the phenology of all species in the alpine plant community is affected by grazing has seldom been monitored. Study Site Qinghai‐Tibetan Plateau of China. Methods A linear mixed model was used to explore the effect of grazing regimes (continuous grazing, grazing exclusion and rotational grazing), species, and individuals of species on phenological stages at the community level. One‐way ANOVA was used to examine the difference in phenological stage across different species under the same grazing regime and timing of the phenological stages of each species across different grazing regimes. Pearson correlation analysis was used to explore linkages between plant phenology and leaf traits, linkages between phenological stages, as well as their intervals across different species. Results The green‐up and withering time of different species both exhibited various response patterns to grazing regimes. The flowering time of most species was delayed by grazing, whereas the fruiting time of most species remained stable across grazing regimes. There were significant linkages between phenological stages and leaf traits; for example fruiting time was negatively related to the ratio of leaf N content (LNC) to leaf P content (LPC) under all grazing regimes. The phenological stages themselves, and their intervals, showed close relations; for example fruiting time was positively related to withering time, and negatively related to its interval. The divergence was higher during the flowering time than during other phenological stages. The divergence of all phenological stages was highest under grazing exclusion. Conclusions The shifts in flowering time were advantageous for these plants to adapt to grazing, as flowering time can regulate interspecific temporal patterns and maintain the stability of subsequent phenological stages. Among grazing regimes, grazing exclusion led to greatest divergence of phenological stages across species, which possibly creates potential reproductive gaps.

Description: Analytical Chemistry DOI: 10.1021/acs.analchem.5b03664