Wee Cheah

Controls of primary production in two phytoplankton blooms in the Antarctic Circumpolar Current

The Antarctic Circumpolar Current has a high potential for primary production and carbon sequestration through the biological pump. In the current study, two large-scale blooms observed in 2012 during a cruise with R.V. Polarstern were investigated with respect to phytoplankton standing stocks, primary productivity and nutrient budgets. While net primary productivity was similar in both blooms, chlorophyll a –specific photosynthesis was more efficient in the bloom closer to the island of South Georgia (39 °W, 50 °S) compared to the open ocean bloom further east (12 °W, 51 °S). We did not find evidence for light being the driver of bloom dynamics as chlorophyll standing stocks up to 165 mg m−2 developed despite mixed layers as deep as 90 m. Since the two bloom regions differ in their distance to shelf areas, potential sources of iron vary. Nutrient (nitrate, phosphate, silicate) deficits were similar in both areas despite different bloom ages, but their ratios indicated more pronounced iron limitation at 12 °W compared to 39 °W. While primarily the supply of iron and not the availability of light seemed to control onset and duration of the blooms, higher grazing pressure could have exerted a stronger control toward the declining phase of the blooms.

Response of Phytoplankton Photophysiology to Varying Environmental Conditions in the Sub-Antarctic and Polar Frontal Zone

Climate-driven changes are expected to alter the hydrography of the Sub-Antarctic Zone (SAZ) and Polar Frontal Zone (PFZ) south of Australia, in which distinct regional environments are believed to be responsible for the differences in phytoplankton biomass in these regions. Here, we report how the dynamic influences of light, iron and temperature, which are responsible for the photophysiological differences between phytoplankton in the SAZ and PFZ, contribute to the biomass differences in these regions. High effective photochemical efficiency of photosystem II (/ 0.4), maximum photosynthesis rate (), light-saturation intensity (), maximum rate of photosynthetic electron transport (1/), and low photoprotective pigment concentrations observed in the SAZ correspond to high chlorophyll and iron concentrations. In contrast, phytoplankton in the PFZ exhibits low / ( 0.2) and high concentrations of photoprotective pigments under low light environment. Strong negative relationships between iron, temperature, and photoprotective pigments demonstrate that cells were producing more photoprotective pigments under low temperature and iron conditions, and are responsible for the low biomass and low productivity measured in the PFZ. As warming and enhanced iron input is expected in this region, this could probably increase phytoplankton photosynthesis in this region. However, complex interactions between the biogeochemical processes (e.g. stratification caused by warming could prevent mixing of nutrients), which control phytoplankton biomass and productivity, remain uncertain.

Quantum yield of the marine benthic microflora of near-shore coastal Penang, Malaysia

Benthic microalgal communities often contribute more than 30% of the primary production of shallow coastal and estuarine areas. At Muka Head Penang (Pulau Pinang) and the Songsong Islands (Pulau Songsong), Kedah, Malaysia, high concentrations of suspended solids and phytoplankton biomass (10.6 mg Chl a m-3) has reduced water clarity such that the euphotic zone of these areas is less than 2 m and 3 m deep respectively. The benthic microalgal communities, which were composed of the diatom genera Cocconeis, Fragilaria, Paralia and Pleurosigma, had a low biomass, had low maximum quantum yields (0.325 ± 0.129), were poorly adapted to their light environment and were constantly light limited. These characteristics suggest that the benthic microalgal communities were likely to have made only a minor contribution to the total primary production of the area.

Highly hydrophilic and nonionic poly(2-vinyloxazoline)-grafted silica: a novel organic phase for high-selectivity hydrophilic interaction chromatography

AbstractA new hydrophilic and nonionic poly(2-vinyloxazoline)-grafted silica (Sil-VOXn) phase was synthesized and applied for the separation of nucleosides and nucleobases in hydrophilic interaction chromatography (HILIC). Polymerization and immobilization onto silica were confirmed by using characterization techniques including 1H NMR spectroscopy, elemental analysis, and diffuse reflectance infrared Fourier transform spectroscopy. The hydrophilicity or wettability of Sil-VOXn was observed by measuring the contact angle (59.9°). The chromatographic results were compared with those obtained with a conventional HILIC silica column. The Sil-VOXn phase showed much better separation of polar test analytes than the silica column, and the elution order was different. Differences in selectivity between these two columns indicate that the stationary phase cannot function merely as an inert support for a water layer into which the solutes are partitioned from the bulk mobile phase. To elucidate the interaction mechanism, the separation of dihydroxybenzene isomers was performed on both columns in normal-phase liquid chromatography. Sil-VOXn was very sensitive to the dipole moments of the positional isomers of polycyclic aromatic compounds in normal-phase liquid chromatography. The interaction mechanism for Sil-VOXn in HILIC separation is also described. FigureSeparation of nucleosides and nucleobases with Sil-VOXn (bottom) and a commercial silica column (top). Mobile phase of acetonitrile and 20 mM ammonium acetate (9:1, v/v). Flow rate 1 ml min-1, column temperature 25 °C. The analytes were as follows 5-iodouracil (1), thymine (2), uracil (3), 4,6-diaminopyrimidine (4), uridine (5), adenosine 2 (6), cytosine (7), cytidine (8), and guanosine (9)

A rare and extensive summer bloom enhanced by ocean eddies in the oligotrophic western North Pacific Subtropical Gyre

The North Pacific Subtropical Gyre (NPSG) is the largest ecosystem on Earth, and it plays a critical role in global ocean productivity and carbon cycling. Here, we report a rare and striking ~2000-km-long phytoplankton bloom that lasted over one month in the western part of the NPSG in summer 2003. The bloom resulted from the co-occurrence of a northward-shifted North Equatorial Current (NEC) supplying additional phosphate, and strong eddy activity that fueled productivity and spread chlorophyll mainly through horizontal stirring. The extensive one-month bloom had a maximum Chl concentration of six times the summer mean value and collectively fixed an additional five teragrams (5 × 1012 g) of carbon above the summer average. An increase in the pCO2 during the bloom suggests that most of the additionally fixed carbon was rapidly consumed.

Preparation and Characterization of Amine-Functionalised SBA-15

Ever since the first report of ordered mesoporous silica by the Mobil group, various preparation techniques for mesoporous were extensively studied. In addition to the desirable large surface area, surface of mesoporous silica could be modified for specific catalytic and sensor applications. In this present study, SBA-15 mesoporous silica was prepared and further surface modification was done using organoalkoxysilane (aminopropyl and ethylendiaminopropyl). The resulting bare mesoporous silica, anime-functionalised and diamine-functionalised mesoporous silica were characterized using FTIR, XRD, SEM and EDS for the analysis of incorporation of amine functional groups, phase analysis, powder morphology and elemental analysis.

Organic and Inorganic Acid Activation of Activated Carbon Fiber from Palm Oil Empty Fruit Bunch

Activated carbon fiber is known to posses better properties compared to granular and powdered variants, with significantly higher surface area and higher pore volume. Source of raw material and activation step are two crucial parameters for the pore development of activated carbon. Palm oil empty fruit bunch fiber contains naturally formed long open channels which offer better access of adsorbates into micropores. Chemical activation step typically involves inorganic acids such as phosphoric acid and sulfuric acid. However, such residues of inorganic acids might create unfavourable conditions for certain adsorption applications, if not removed properly from synthesized activated carbon fiber. Additionally, subsequent to the acid cleaning or removal step, most inorganic acids would eventually cause problems to the environment if acid disposal is not properly managed. This paper investigates on the effect of utilization of organic acids acetic acid and citric acid, as compared to commonly used inorganic acids, on the pore characteristics of palm oil empty fruit bunch fiber derived activated carbon fiber.