Profiling the transcriptome of Gracilaria changii (Rhodophyta) in response to light deprivation

Light regulates photosynthesis, growth and reproduction, yield and properties of phycocolloids, and starch contents in seaweeds. Despite its importance as an environmental cue that regulates many developmental, physiological, and biochemical processes, the network of genes involved during light deprivation are obscure. In this study, we profiled the transcriptome of Gracilaria changii at two different irradiance levels using a cDNA microarray containing more than 3,000 cDNA probes. Microarray analysis revealed that 93 and 105 genes were up- and down-regulated more than 3-fold under light deprivation, respectively. However, only 50% of the transcripts have significant matches to the nonredundant peptide sequences in the database. The transcripts that accumulated under light deprivation include vanadium chloroperoxidase, thioredoxin, ferredoxin component, and reduced nicotinamide adenine dinucleotide dehydrogenase. Among the genes that were down-regulated under light deprivation were genes encoding light harvesting protein, light harvesting complex I, phycobilisome 7.8 kDa linker polypeptide, low molecular weight early light-inducible protein, and vanadium bromoperoxidase. Our findings also provided important clues to the functions of many unknown sequences that could not be annotated using sequence comparison

Characterisation of particle mass and number concentration on the east coast of the Malaysian Peninsula during the northeast monsoon

Particle mass concentrations (PM10, PM2.5 and PM1) and particle number concentration ((PNC); 0.27 μm ≤ Dp ≤ 34.00 μm) were measured in the tropical coastal environment of Bachok, Kelantan on the Malaysian Peninsula bordering the southern edge of the South China Sea. Statistical methods were applied on a three-month hourly data set (9th January to 24th March 2014) to study the influence of north-easterly winds on the patterns of particle mass and PNC size distributions. The 24-h concentrations of particle mass obtained in this study were below the standard values detailed by the Recommended Malaysian Air Quality Guideline (RMAQG), United States Environmental Protection Agency (US EPA) and European Union (EU) except for PM2.5, which recorded a 24-h average of 30 ± 18 μg m-3 and exceeded the World Health Organisation (WHO) threshold value (25 μg m-3). Principal component analysis (PCA) revealed that PNC with smaller diameter sizes (0.27-4.50 μm) showed a stronger influence, accounting for 57.6% of the variability in PNC data set. Concentrations of both particle mass and PNC increased steadily in the morning with a distinct peak observed at around 8.00 h, related to a combination of dispersion of accumulated particles overnight and local traffic. In addition to local anthropogenic, agricultural burning and forest fire activities, long-range transport also affects the study area. Hotspot and backward wind trajectory observations illustrated that the biomass burning episode (around February-March) significantly influenced PNC. Meteorological parameters influenced smaller size particles (i.e. PM1 and Dp (0.27-0.43 μm)) the most

Growth Response, Biochemical Composition and Fatty Acid Profiles of Four Antarctic Microalgae Subjected To UV Radiation Stress

The effects of ultra-violet radiation (UVR) stress on the growth, biochemical composition and fatty acid profiles of four Antarctic microalgae from the University of Malaya Algae Culture Collection (UMACC) were investigated. The microalgae studied were Chlamydomonas UMACC 229, Navicula UMACC 231, Chlorella UMACC 237 and Klebsormidium UMACC 227 which were isolated from samples collected from Casey Station, Antarctica. Three experiments were conducted. In the first experiment, the cultures were exposed to to days of high UVB (515 µWcm⁻²) + Photosynthetically Active Radiation (PAR), UVA (845 µWcm⁻²) + PAR, and PAR alone. In the second experiment, the cultures were illuminated for to days with low UVB (117 µWcm⁻²) + PAR and PAR alone. In the third experiment, the cultures were subjected to short-term (48 hours) exposure of low UVB (117 µWcm⁻²) + PAR and PAR alone. There was no marked difference amongst the four Antarctic microalgae in terms of their growth response to UVB. All the species tested did not grow well after exposure to low (117 µWcm⁻²) or high (515 µWcm⁻²) UVB for 10 days. In contrast, exposure of UVA at 845 µWcm-2 for to days did not affect the growth of the microalgae. Growth of the cultures exposed to UVA for 48 h was only slightly affected compared to those exposed to PAR alone. The effects of UVR on lipid, carbohydrate and protein content did not show consistent trends. However, exposure to UVB resulted in marked decrease of the percentage of polyunsaturated fatty acids (PUFA) in the four microalgae. Thus, fatty acid profile is a distinct biomarker for UVR stress

Ruthenium oxide/tungsten oxide composite nanofibers as anode catalysts for the green energy generation of Chlorella vulgaris mediated biophotovoltaic cells

The development of electrochemically active and stable anode catalysts for the photoelectrochemical splitting of water molecules via biophotovoltaic cells (BPVs) utilizing microalgae receives a prime importance in green energy sector. Herein, we report the ruthenium oxide (RuO2)/tungsten oxide (WO3) composite nanofibers based photoanode for the application of high performance and durable BPV. The sequential arrangement of 6 nm sized RuO2/WO3 spherical particles constitutes the nanofibrous morphology and a number of surface active sites and structural integrity of nanofibers demonstrate the excellent and stable photo-oxidation currents. Under the light regime, RuO2/WO3/carbon cloth photoanode exhibits the substantial BPV power and current densities with an excellent durability. Thus this systematic study evokes the fundamental understanding on the electron generation and transference mechanisms, which offers new dimensions in the development of high performance and durable BPVs. © 2019 American Institute of Chemical Engineer

Potential for Future Threats to Ozone Recovery from 'Short' and 'Very Short-lived' Halocarbons

International audienc

Can seaweed farming in the tropics contribute to climate change through emission of short-lived halocarbons?

Volatile halocarbons form a major source of halogen radicals in the atmosphere, which are in- volved in the catalytic destruction of ozone. Studies show that marine algae release halocarbons, with 70% of global bromoform produced by marine algae (Carpenter et al., 2000). The role of halocarbons in algae is linked to their use as defense against epiphytes and grazing as well as scavengers of strong oxidants (Nightingale et al., 1995). Halo- carbon release rates are higher for tropical algae than temperate species (Abrahamsson et al., 1995). The Maritime Continent is a major contributor to emissions of short-lived halocarbons and their transport to the stratosphere due to deep convection. The Coral Triangle situated in the Maritime Continent, is a centre for seaweed farming. The fol- lowing discusses the potential impact of tropical seaweed emissions of halogenated compounds to climate change

Cloud-scale modelling of the impact of deep convection on the fate of oceanic bromoform in the troposphere:a case study over the west coast of Borneo

This paper presents a modelling study on the fate of CHBr3 and its product gases in the troposphere within the context of tropical deep convection. A cloud-scale case study was conducted along the west coast of Borneo, where several deep convective systems were triggered on the afternoon and early evening of 19 November 2011. These systems were sampled by the Falcon aircraft during the field campaign of the SHIVA project and analysed using a simulation with the cloud-resolving meteorological model C-CATT-BRAMS at 2×2 km resolution that represents the emissions, transport by large-scale flow, convection, photochemistry, and washout of CHBr3 and its product gases (PGs). We find that simulated CHBr3 mixing ratios and the observed values in the boundary layer and the outflow of the convective systems agree. However, the model underestimates the background CHBr3 mixing ratios in the upper troposphere, which suggests a missing source at the regional scale. An analysis of the simulated chemical speciation of bromine within and around each simulated convective system during the mature convective stage reveals that >85 % of the bromine derived from CHBr3 and its PGs is transported vertically to the point of convective detrainment in the form of CHBr3 and that the remaining small fraction is in the form of organic PGs, principally insoluble brominated carbonyls produced from the photo-oxidation of CHBr3. The model simulates that within the boundary layer and free troposphere, the inorganic PGs are only present in soluble forms, i.e. HBr, HOBr, and BrONO2, and, consequently, within the convective clouds, the inorganic PGs are almost entirely removed by wet scavenging. We find that HBr is the most abundant PG in background lower-tropospheric air and that this prevalence of HBr is a result of the relatively low background tropospheric ozone levels at the regional scale. Contrary to a previous study in a different environment, for the conditions in the simulation, the insoluble Br2 species is hardly formed within the convective systems and therefore plays no significant role in the vertical transport of bromine. This likely results from the relatively small quantities of simulated inorganic bromine involved, the presence of HBr in large excess compared to HOBr and BrO, and the relatively efficient removal of soluble compounds within the convective column