Flexibility of Microcystis Overwintering Strategy in Response to Winter Temperatures

Microcystis is one of the most common bloom-forming cyanobacteria in freshwater ecosystems throughout the world. However, the underlying life history mechanism and distinct temporal dynamics (inter- and intra-annual) of Microcystis populations in different geographical locations and lakes remain unclear but is critical information needed for the development of robust prediction, prevention, and management strategies. Perennial observations indicate that temperature may be the key factor driving differences in the overwintering strategy. This study quantitatively compared the overwintering abilities of Microcystis aeruginosa (Ma) in both the water column and sediments under a gradient of overwintering water temperatures (i.e., 4, 8, and 12 °C) using the death and proliferation rates of Ma. The results show that the dynamics of the Microcystis overwintering strategy were significantly affected by water temperatures. At 4 and 8 °C, Ma mainly overwintered in sediments and disappeared from the water column after exposure to low temperatures for a long duration, although some Microcystis cells can overwinter in the water column for short durations at low temperatures. At 12 °C, most Ma can overwinter in the water column. Rising temperatures promoted the proliferation of pelagic Ma but accelerated the death of benthic Ma. With warmer winter temperatures, pelagic Microcystis might become the primary inoculum sources in the spring. Our study highlights the overwintering strategy flexibility in explaining temporal dynamics differences of Microcystis among in geographical locations and should be considered in the context of global warming

Flexibility of <i>Microcystis</i> Overwintering Strategy in Response to Winter Temperatures

Microcystis is one of the most common bloom-forming cyanobacteria in freshwater ecosystems throughout the world. However, the underlying life history mechanism and distinct temporal dynamics (inter- and intra-annual) of Microcystis populations in different geographical locations and lakes remain unclear but is critical information needed for the development of robust prediction, prevention, and management strategies. Perennial observations indicate that temperature may be the key factor driving differences in the overwintering strategy. This study quantitatively compared the overwintering abilities of Microcystis aeruginosa (Ma) in both the water column and sediments under a gradient of overwintering water temperatures (i.e., 4, 8, and 12 °C) using the death and proliferation rates of Ma. The results show that the dynamics of the Microcystis overwintering strategy were significantly affected by water temperatures. At 4 and 8 °C, Ma mainly overwintered in sediments and disappeared from the water column after exposure to low temperatures for a long duration, although some Microcystis cells can overwinter in the water column for short durations at low temperatures. At 12 °C, most Ma can overwinter in the water column. Rising temperatures promoted the proliferation of pelagic Ma but accelerated the death of benthic Ma. With warmer winter temperatures, pelagic Microcystis might become the primary inoculum sources in the spring. Our study highlights the overwintering strategy flexibility in explaining temporal dynamics differences of Microcystis among in geographical locations and should be considered in the context of global warming

A novel integrative performance evaluation of constructed wetland on removal of viable bacterial cells and related pathogenic, virulent and multi-drug resistant genes from wastewater systems

Integrative performance evaluation of constructed wetland in removal different aspects of bacteria under specific local environmental conditions needs to be explored in detail to ensure selection of appropriate and highly efficient macrophytes candidates. To achieve this, integrative purification performance evaluation approach that holistically considers all the aspects of pathogenic bacterial biology (colony numbers, functional gene, species, virulent, pathogenicity and resistant genes) needs to be adopted rather than the commonly known unidimensional approaches that take into account a single bacterial aspect. This study experimentally evaluated the individual performance of three native and one exotic winter tolerant submerged macrophytes combined with a single emergent macrophyte in eradicating faecal related bacterial species and pathotypes across horizontal surface flow constructed wetland. It involved the new multi-dimensional approach that integrated the faecal bacterial colony numbers, functional gene copies, species survival, virulent and pathogenicity as well as antimicrobial resistant in constructed wetland purification evaluation. The results showed Elodea nuttallii and Myriophyllum spicatum as the best candidate partners to Typha latifolia for the highest Purification Efficiency (P &lt; 0.05), of above 97% for removal of faecal bacteria colonies and functional genes, and more than 75% for removal of faecal bacterial strains, pathotypes, virulent and well as resistant genes. However, M. spicatum being a Chinese native species should be much preferred to the invasive E. nuttallii. Therefore, the study recommends the application of local macrophytes such as M. spicatum as the best candidates and the decision should emanate from such a multidimensional/intergrative purification-based evaluation approach.</p