Hongze Lake is a large, shallow, polymictic, eutrophic lake in the eastern China. Phytoplankton functional groups in this lake were investigated from March 2011 to February 2013, and a comparison was made between the eastern, western, and northern regions. The lake shows strong fluctuations in water level caused by monsoon rains and regular hydraulic controls. By application of the phytoplankton functional group approach, this study aims to investigate the spatial and temporal dynamics and analyze their influencing factors. Altogether, 18 functional groups of phytoplankton were identified, encompassing 187 species. In order to seek the best variable describing the phytoplankton functional group distribution, 14 of the groups were analyzed in detail using redundancy analysis. Due to the turbid condition of the lake, the dominant functional groups were those tolerant of low light. The predominant functional groups in the annual succession were D (Cyclotella spp. and Synedra acus), T (Planctonema lauterbornii), P (Fragilaria crotonensis), X1 (Chlorella vulgaris and Chlorella pyrenoidosa), C (Cyclotella meneghiniana and Cyclotella ocellata), and Y (Cryptomonas erosa). An opposite relationship between water level and the biomass of predominant groups was observed in the present study. Water level fluctuations, caused by monsoonal climate and artificial drawdown, were significant factors influencing phytoplankton succession in Hongze Lake, since they alter the hydrological conditions and influence light and nutrient availability. The clearly demonstrated factors, which significantly influence phytoplankton dynamics in Hongze Lake, will help government manage the large shallow lakes with frequent water level fluctuations.

Live green microalgae Chlorella pyrenoidosa was introduced in the anode of a microbial fuel cell (MFC) to act as an electron donor. By controlling the oxygen content, light intensity, and algal cell density at the anode, microalgae would generate electricity without requiring externally added substrates. Two models of algal microbial fuel cells (MFCs) were constructed with graphite/carbon electrodes and no mediator. Model 1 algal MFC has live microalgae grown at the anode and potassium ferricyanide at the cathode, while model 2 algal MFC had live microalgae in both the anode and cathode in different growth conditions. Results indicated that a higher current produced in model 1 algal MFC was obtained at low light intensity of 2500 lx and algal cell density of 5 × 10⁶ cells/ml, in which high algal density would limit the electricity generation, probably by increasing oxygen level and mass transfer problem. The maximum power density per unit anode volume obtained in model 1 algal MFC was relatively high at 6030 mW/m², while the maximum power density at 30.15 mW/m² was comparable with that of previous reported bacteria-driven MFC with graphite/carbon electrodes. A much smaller power density at 2.5 mW/m² was observed in model 2 algal MFC. Increasing the algal cell permeability by 4-nitroaniline would increase the open circuit voltage, while the mitochondrial acting and proton leak promoting agents resveratrol and 2,4-dinitrophenol would increase the electric current production in algal MFC.

Handling of two nitro-aromatic compounds, 4-nitroaniline (4NA) and 4-nitrophenol (4NP), simultaneously by Chlorella pyrenoidosa was investigated. Algae would secrete or degrade nitro-aromatic compounds depending on different environmental conditions, in which the mode of handling was determined by the relative formation and degradation rate of the compound. Repeated intermittent trigger with externally added 4NA would induce the continuous secretion of 4NA by algae. Simultaneous exposure of both 4NA and 4NP to algae at normal condition would induce the algae to secrete both compounds. An increase in 4NA exposure concentration would elevate both 4NA and 4NP secretion, and that would be inhibited by the stress conditions of starving or lack of oxygen. Increased 4NA degradation per production rate induced by starving or lack of oxygen might explain the subsequent decrease in 4NA secretion in the presence of 4NP in algae. For 4NP in the presence of 4NA, secretion at normal condition was completely stopped and turned to degradation mode in stress conditions. The decreased formation and increased degradation of 4NP during starving for replenishing energy would explain the net degradation of 4NP in starving condition. The condition of lack of oxygen would inhibit the 4NP formation from 4NA via oxidative deamination, while the degradation of 4NP might not be significantly affected because alternative pathway of degradation via nitro-reduction was available. It may lead to the degradation rate exceeding the formation and explain the net degradation of 4NP in the condition of lack of oxygen.