Light is an important factor that affects cyanobacterial growth and changes in light can influence their growth and physiology. However, an information gap exists regarding light-induced oxidative stress and the species-specific behavior of cyanobacteria under various light levels. This study was conducted to evaluate the comparative effects of different light intensities on the growth and stress responses of two cyanobacteria species, Pseudanabaena galeata (strain NIES 512) and Microcystis aeruginosa (strain NIES 111), after periods of two and eight days. The cyanobacterial cultures were grown under the following different light intensities: 0, 10, 30, 50, 100, 300, and 600 μmol m−2 s−1. The optical density (OD730), chlorophyll a (Chl-a) content, protein content, H2O2 content, and the antioxidative enzyme activities of catalase (CAT) and peroxidase (POD) were measured separately in each cyanobacteria species. P. galeata was negatively affected by light intensities lower than 30 μmol m−2 s−1 and higher than 50 μmol m−2 s−1. A range of 30 to 50 μmol m−2 s−1 light was favorable for the growth of P. galeata, whereas M. aeruginosa had a higher tolerance for extreme light conditions. The favorable range for M. aeruginosa was 10 to 100 μmol m−2 s−1.

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The insertion of microelectrodes into plants to record electric potentials can generate electric potential responses due to disturbance of plant tissues. Here, the electric potential triggered by Ag/AgCl glass microelectrode insertion into the stele of Myriophyllum aquaticum (parrot feather) plants was recorded. A system potential was triggered upon the electrode insertion and was propagated along the stele of the stem. The microelectrode detected this electric potential that was triggered by its own insertion and the electric potential was identical among the plants assessed. The temporal variation in electric potential registered two prominent peaks at 31.9 ± 1.8 and 17.1 ± 4.3 mV. The electric potential was repolarized after approximately 50-70 min and the stabilized electric potential was 6.5 ± 2.5 mV higher than the initial electric potential of plants. Control experiments conducted using a non-biological spongy rod wetted with distilled water or 1 M KCl confirmed that the peaks were solely due to the electric potential in the stem. These signals can be recognized as system potentials. The systematic EP could develop stimuli responses in distant locations, which is to be tested in further studies.

The ecological dynamics of riparian areas interact with sediment transport in river systems, which plays an active role in riparian vegetation growth in the floodplain. The fluvial dynamics, hydraulics, hydro-meteorological and geomorphological characteristics of rivers are associated with sediment transport in river systems and around the riparian area. The flood disturbance, sediment with nutrients and seeds transported by river, sediment deposition, and erosion phenomena in the floodplain change the bare land area to vegetation area and vice versa. The difference in riparian vegetation area in the river floodplain is dependent on the sediment grain size distribution which is deposited in the river floodplain. Mathematical models describing vegetation growth in a short period exist in literature, but long-term modelling and validations are still lacking. In order to cover long-term vegetation growth modelling, a Dynamic Riparian Vegetation Model (DRIPVEM) was proposed. This paper highlights the existing modelling technique of DRIPVEM coupled with a Dynamic Herbaceous Model used to establish the interactive relationship of sediment grain sizes and riparian vegetation in the floodplain.

Two harmful cyanobacteria species (Phormidium ambiguum and Microcystis aeruginosa) were exposed to diurnal light-intensity variation to investigate their favorable and stressed phases during a single day. The photosynthetically active radiation (PAR) started at 0 µmol·m−2·s−1 (06:00 h), increased by ~25 µmol·m−2·s−1 or ~50 µmol·m−2·s−1 every 30 min, peaking at 300 µmol·m−2·s−1 or 600 µmol·m−2·s−1 (12:00 h), and then decreased to 0 µmol·m−2·s−1 (by 18:00 h). The H2O2 and antioxidant activities were paralleled to light intensity. Higher H2O2 and antioxidant levels (guaiacol peroxidase, catalase (CAT), and superoxidase dismutase) were observed at 600 µmol·m−2·s−1 rather than at 300 µmol·m−2·s−1. Changes in antioxidant levels under each light condition differed between the species. Significant correlations were observed between antioxidant activities and H2O2 contents for both species, except for the CAT activity of P. ambiguum at 300 µmol·m−2·s−1. Under each of the conditions, both species responded proportionately to oxidative stress. Even under maximum light intensities (300 µmol·m−2·s−1 or 600 µmol·m−2·s−1 PAR intensity), neither species was stressed. Studies using extended exposure durations are warranted to better understand the growth performance and long-term physiological responses of both species.