High-resolution light-induced kinetics of chlorophyll fluorescence (OJIP transients) were recorded and analyzed in cultures of diatoms (Thalassiosira weissflogii, Chaetoceros mulleri) and dinoflagellates (Amphidinium carterae, Prorocentrum minimum). Fluorescence transients showed the rapid exponential initial rise from the point O indicating low connectivity between PS II units and high absorption cross-section of PS II antenna. Dark-adapted dinoflagellates revealed capability to maintain the PS I-mediated re-oxidation of the PQ pool at the exposure to strong actinic light that may lead to the underestimation of F(M) value. In OJIP transients recorded in phytoplanktonic algae the fluorescence yield at the point O exceeded F(O) level because Q(A) has been already partly reduced at 50 micros after the illumination onset. PEA was also employed to study the recovery of photosynthetic reactions in T. weissflogii during incubation of nitrogen starved cells in N-replete medium. N limitation caused the impairment of electron transport between Q(A) and PQs, accumulation of closed PS II centers, and the reduced ability to generate transmembrane DeltapH upon illumination, almost fully restored during the recovery period. The recovered cells showed much higher values of NPQ than control ones suggesting maximization of photoprotection mechanisms in the population with a 'stress history.'

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The process of cultivation of microalgae on purified and clarified wastewater of Kuryanovo wastewater treatment plants (KWWTP) was studied. The studies were conducted on monoculture (Scenedesmus quadricauda and Chlorella sorokiniana) and on polyculture, the composition of which was formed from microalgae present in the wastewater. The authors created and investigated the columnar photobioreactor (PBR), which acted as a pilot project on the purified and clarified water of KWWTP and allowed the removal of total nitrogen and phosphorus phosphates with an efficiency of up to 90%. The formation of a stable biocenosis from 22 species of algae (with 3-4 dominant species) and 31 species of zooplankton organisms belonging to six systematic subdivisions was recorded. The optimal retention time of the microalgae polyculture for the most effective wastewater treatment has been determined. The conducted studies have shown that the depth of decomposition of ashless matter and the ultimate biogas potential of untreated microalgae biomass is 15% lower than the corresponding values obtained with digestion of activated sludge, which necessitates studies in the field of pretreatment of algal biomass. The paper shows: connections between chlorophyll-a content, algal biomass and fluorescence index F and between biomass increment and Fv/Fm value.

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The spectral composition of sunlight in natural aquatic habitats depends on the depth of submer gence and the solar time. Changes in the fractional amount of far red light (FRL) in the total photon flux are associated with the redistribution of light energy absorbed by the two photosystems of photosynthesis. Exper iments with a culture of Scenedesmus quadricauda revealed the influence of FRL preillumination on photo synthetic electron transport and associated processes in microalgae. The plant efficiency analyzer M PEA 2 was used to measure simultaneously the induction curves of prompt fluorescence, delayed fluorescence, and the redox transients of chlorophyll P700. The results are discussed in terms of the action of FRL preillumi nation on cyclic and noncyclic electron flows with account for relocation of the mobile light harvesting com plex of photosystem II during reversible State 1-State 2 transitions. Essential similarities and substantial dis tinctions have been revealed in the effects of FRL on photosynthetic electron flows in microalgae and higher plant leaves.Abbreviations: DF-delayed chlorophyll fluorescence; FNRferredoxin NADP reductase; FRL-far red light; P700-the pigment of photosystem I reaction center; PF-prompt fluores cence; PQ-plastoquinone; PSI and PSII-photosystems I and II; Q A and Q B -the primary and secondary quinones serving as elec tron acceptors in PSII.