Comparing Harvest Productivity of the Filamentous Alga Oedogonium with Microalgae

As the planet is faced with depletion of its natural resources, alternative and sustainable energy sources are becoming increasingly sought after. Research on the growth of algae has revealed their potential for carbon capture to reduce greenhouse gas emissions and for conversion into a fuel source for bioenergy applications. Filamentous algae have attracted recent attention as an optimal species due to their ease of harvest and dominance over other species. To determine the most suitable species for future biomass applications, a 1000-L open raceway pond was inoculated with the freshwater filamentous alga, Oedogonium. The pond culture was harvested weekly to determine the effects of CO2 addition on culture density (mg VSS/L) and harvest productivity (g VSS/m2-day). An additional two 1000-L raceway ponds with established cultures of microalgae already receiving CO2 were used as a comparison to the growth of Oedogonium. After 3 weeks, Oedogonium harvest productivity exceeded both microalgal ponds at 13.7 (± 0.2) g VSS/m2-day compared to 9.3 (± 0.7) and 9.5 (± 0.3) g VSS/m2-day for the microalgae.

Oxygen evolution rate in Antarctic filamentous alga Stigeoclonium sp. evaluated by optodes relates to chlorophyll fluorescence parameters (Short Communication)

Photosynthetic reactions of algal communities, the essential component of primary production in polar regions, are strongly dependent on environmental factors. Among them, availability and amount of light in particular parts of growing season are of major importance. In this paper, the response of the photosynthetic processes of a filamentous fresh-water alga to photosynthetically active radiation (PAR) was studied by two approaches. The simultaneous measurements of the effective quantum yield (FPSII) and oxygen evolution rate (OER) at stepwise increasing photosynthetically active radiation provided data for beneficial correlation analysis of the FPSII to OER relationship in a wide range of PAR. In this study, the culture of filamentous alga Stigeoclonium sp. was analyzed. The linear relationship between FPSII and OER was found for the low PAR (the range of 0 – 200 mmol.m-2.s-1). At high PAR levels (200 – 1000 mmol.m-2.s-1) another linear relationship with different slope was found. The approach combining the fluorometric and oxymetric method might be used for calibration of data in follow up studies and, consequently for evaluation of photosynthetic rates (O2 evolution) from chlorophyll fluorescence data.

Effects of heavy metals ions on primary photosynthetic processes in Antarctic filamentous alga Zygnema sp. ( Short Communication )

Algae show different extent of resistance to heavy metals. In this study, the resistance of green filamentous alga Zygnema sp. (strain EEL201, originally collected at James Ross Island, Antarctica) was tested by chlorophyll fluorescence parameters. The alga was taken from the stock culture cultivated on agar, innoculated to liquid medium and allowed to develop biomass large enough for exposition experiments. Heavy metal treatments consisted of addition of Cd and Zn so that effective concentration was 66 mM. Response of primary photosynthetic processes to Cd, Zn addition was assessed by the exposition time-dependent decrease in potential quantum yield (FV/FM) photosystem II (PS II) and relative fluorescence decline ratio (RFd). Cd- and Zn-treated Zygnema sp. exhibited similar extent of decline of the two parameters associated with inhibition of primary processes of photosynthesis. Negative changes to PS II, however, did not bring full inhibition of PS II functioning since FV/FM was about 0.450 after 120 min. exposition. The results might indicate a potential of Antarctic Zygnema in the studies focused on resistance to heavy metals and phytoremediation technologies.

UV-B effects on filamentous alga Zygnema strain (EEL201) from Antarctica

Filamentous alga Zygnema sp. is frequently found in extreme polar environments with freshwater availability for at least part of summer season. In such habitats, Zygnema might be exposed to several stress factors, like freeze, desiccation and high irradiation levels. This study investigated the effect of UV-B on primary photosynthetic processes in Zygnema sp. (EEL201 strain) from Antarctica. Samples were cultivated in liquid medium and exposed to supplemental UV-B (1.4 W m-2) for 6 h. During the UV-B treatment and following recovery, the changes in chlorophyll fluorescence paramaters caused UV-B were measured. Negative effects on FV/FM and FPSII were found after 6 h treatment with only limited recovery in dark. The only parameter that recovered was photochemical quenching (qP) indicating a potential to restore photosynthesis in the reaction centres that were not damaged by UV-B treatment. However, the share on damaged RC PS II was much higher compared to those showing the recovery. Thus, the effect of short-term supplemental 1.4 W m-2 UV-B light was considered heavy causing substantial damages to PS II. These results provide insights on the effects of UV-B light onZygnemasp. that can help in the interpretation of response mechanisms of Arctic algae to radiation.

Antarctic strain of green filamentous alga Zygnema sp. shows a high resistance to photoinhibition under simulated polar conditions

This study deals with treatment-dependent differences in sensitivity of Antarctic filamentous alga Zygnema sp. to photoinhibition. Zygnema sp. (strain EEL201) was collected at the James Ross Island, Antarctica (57° 52´ 57´´ W, 63° 48´ 02´´ S). In a laboratory, the alga was cultivated on agar first and then innoculated to liquid medium. They were exposed to a short-term (30 min.) high light (HL) treatments. Particular treatments comprised 600, 1 400 and 2 100 and 3 500 μmol m-2 s-1 of photosynthetically active radiation (PAR). Photosynthetic efficiency of Zygnema sp. in individual HL treatments was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. Zygnema sp. showed a high resistance to HL since it both chlorophyll fluorescence parameters recovered to about 70% of initial values after 4 h in dark. Chlorophyll fluorescence measured immediately after particular treatment, showed HL-dependent decrease in absolute values of chlorophyll fluorescence signal and consequent uncompleted recovery as well. Quenching of F0, an indicator of changes in light-harvesting complexes of photosystem II, did not show dose-dependent response, however, general trend was a decrease found immediately HL treatment with consequent uncompleated recovery. In general, Zygnema sp. exhibited high resistance to PAR doses that the species can whitness in the field during austral summer. Thus the species could be considered highly adapted for high light and has effective mechanisms to cope with photoinhibition. Involvement of particular photoprotective mechanism, their activation and share in natural environment is a topic for future studies.