Impacts of Hydrogen Peroxide and Copper Sulfate on the Control of Microcystis aeruginosa and MC-LR and the Inhibition of MC-LR Degrading Bacterium Bacillus sp.

Laboratory batch experiments were carried out to evaluate the impacts of H2O2 and copper sulfate on M. aeruginosa PCC7820, microcystin-LR (MC-LR) and its degrading bacteria Bacillus sp., previously isolated from Hulupi Lake in Taiwan. The study shows that 3 mg·L−1 hydrogen peroxide removed only 9% M. aeruginosa within seven days of exposure, from an initial cell concentration of 2 × 106 cells/mL. With copper sulfate, a concentration of 2 mg·L−1 removed 99% M. aeruginosa cells, but showed negligible efficacy in removing 0.05 mg·L−1 MC-LR. At a higher dosage, 20 mg·L−1 H2O2 led to 40% and 95% removal, respectively for MC-LR and M. aeruginosa cells. Copper sulfate and H2O2 were both lethal to Bacillus sp. population, with mortality rate constants of k = 0.04 h−1 and 0.03 h−1 under 1 mg·L−1 copper sulfate and 5 mg·L−1 H2O2, respectively. H2O2 is competitive in terms of cost, with a capability of degrading organic compounds with the assistance of ultraviolet (UV) light, and it may be considered as an alternative algaecide to copper sulfate in reservoirs for algae growth control

Microcystin-LR Biodegradation by Bacillus sp.: Reaction Rates and Possible Genes Involved in the Degradation

Harmful cyanobacteria blooms may deteriorate freshwater environments, leading to bad water quality that can adversely affect the health of humans, animals, and aquatic life. Many cyanobacteria can produce toxic metabolites, with Microcystin-LR (MC-LR) being the most commonly detected cyanotoxin in fresh water bodies. In this study, a MC-LR degrading Bacillus sp. strain was isolated from Hulupi Lake (HLPL), Taiwan and tested for its degradability of the cyanotoxin. The results showed that the degradation of Microcystin-LR by the isolated Bacillus sp. was temperature-dependent with an optimum MC-LR removal at 37 °C and a first order degradation constant rate for 0.22 day−1. The degradation rate was also found to increase with decreasing MC-LR concentrations and increasing Bacillus sp. concentrations. Biomolecular monitoring of three types of genes (mlrA, CAAX, and GST) involved in the degradation indicated that mlrA, and CAAX genes were present in the indigenous bacteria in HLPL water samples. However, for the isolated Bacillus sp. strain, only CAAX genes were detected. The absence of the mlrA gene in the isolated Bacillus sp. strain shows that the degradation of MC-LR does not necessarily follow the pathways with mlrA, and can also follow the pathways involved with CAAX type II amino-terminal protease

Patterns of Meteorological Drought Using Standardized Precipitation Evapotranspiration Index for Massili Basin, Burkina Faso

As a Semi-arid country, Burkina Faso is highly vulnerable to climate-related disasters such as drought and flood. Analyzing drought signature is therefore a key factor in advocating climate change adaptation at the local scale. In this study, Spatiotemporal trends of drought were conducted for the period 1960–2021 within Massili Basin using the standardized precipitation and evapotranspiration index (SPEI) package in R. The non-parametric method (Mann–Kendall) was then used to test for a monotonic trend, whereas the magnitude was estimated using Sen's method. Accordingly, the result revealed that during the period 1960-1979, the mean value of SPEI varies from 0.06 to 0.71; over 1980 to 2009, the mean value of the SPEI varies from -0.08 to -0.88 and for the last decades (2010 to 2021), the mean value of the SPEI ranges from 0.05 to 0.75. Normal to middle wet conditions is thus observed over the periods 1960-1979 and 2010-2021 while the period (1980-2009) depicts a middle drought condition. The Mann-Kendall test results show a decreasing trend of SPEI-3 and SPEI-24 with a Z value of - 0.784 and -0.530 respectively. A slightly increasing trend is observed for SPEI-6 and SPEI-12 with Z ranging from 0.598 to 1.917 respectively. The magnitude of the decrease is indicated by the sens’ slope value, which is -0.0014 for SPEI-3 and -0.00010 for SPEI-24 while the magnitude of the increase ranges from 0.00011 for SPEI-6 to 0.00037 for SPEI-12. This study highlights the importance of examining past drought features to obtain essential information to assist in designing and implementing efficient water resources management strategies over the Massili Basin