Effects of different phosphorus concentrations and N/P ratios on the growth and photosynthetic characteristics of Skeletonema costatum and Prorocentrum donghaiense

The effects of different phosphorus(P) concentrations(0.36, 3.6, and 36 μmol/L corresponding to low-, middle-, and high-P concentration groups, respectively) and nitrogen(N)/P ratios on the growth and photosynthetic characteristics of S keletonema costatum and Prorocentrum donghaiense were studied. For both species, the high-P(HP) concentration group showed the greatest algal density and highest specifi c growth rate. Changes in the maximum effi ciency of photosystem Ⅱ(F _v/F_m) were monitored under the various P and N/P conditions. The largest decrease in F _v/F_m was in the low-P(LP) group in S. costatum and in the HP group in P. donghaiense. There were high rapid light curves and photochemical quantum yields(Φ _(PSⅡ)) for S. costatum in the HP group, while the actual photosynthetic capacity was higher in P. donghaiense than in S. costatum in the MP group. Under eutrophic but relatively P-restricted conditions, P. donghaiense had higher photosynthetic activity and potential, which could cause this dinofl agellate to increasingly dominate the phytoplankton community in these conditions. Under the same P concentration and N/P ratio, P. donghaiense had a larger relative maximum rate of electron transport and higher Φ _(PSⅡ) values than those of S. costatum. These differences between P. donghaiense and S. costatum may explain the interaction and succession patterns of these two species in the Changjiang(Yangtze) River estuary from a photosynthesis perspective.

Composite Mesh Electrodes with Immobilized Bacteria for Bio-Batteries

An anode was constructed using a novel technique and subsequently tested in a bio-battery. The anode comprised of a composite electrode coated with immobilized bacteria. The immobilized bacteria used in this study were Escherichia coli K-12. The composite electrode contained three layers: a 304 L stainless steel mesh base, an electro-polymerized layer of pyrrole, and an electro-polymerized layer of methylene blue. The bacteria were immobilized utilizing a technique incorporating a carbon nanoparticle and TeflonTM emulsion. The composite electrode combined with immobilized bacteria was examined whilst incorporated into the anodic chamber of a bio-battery. Different tests were conducted, including Electrochemical Impedance Spectroscopy. Results from these tests were compared with data obtained from alternate configurations and values from the open literature. The maximum power density generated by the composite electrode with immobilized bacteria whilst incorporated into the anodic chamber of a bio-battery was 378 mW/m2. Results demonstrate this composite anode configuration with immobilized bacteria produced approximately 69% more power density and 53% more current density than alternate electrode configurations with bacteria suspended in solution. Also, it was found that a significant portion of the bio-battery’s resistance to charge transfer occurred at the surface of the anode and this resistance was lowered by 51% through bacteria immobilization.

Measurement of algae PSII photosynthetic parameters using high-frequency excitation flashes

We establish a system to measure the functional absorption cross section of photosystem lI （PSII） （O-PSII） and maximum quantum yield of photochemistry in PSII （Fv/Fm）. The system utilizes a sequence of high-frequency excitation flashes at microsecond intervals to induce a microsecond-level fluorescence yield curve. Parameters o-Psii and Fv/Fm are calculated by fitting the curve using nonlinear regression. Experimental results show that the relative standard deviation （RSD） of the system is less than 3%, and the correlation coefficient of Fv/Fm values measured by this system and those measured by pulse amplitude modulation method is 0.950.