Recruitment of cyanobacteria from the sediments in the eutrophic Shanzi Reservoir

Abstract

This study investigated the impact of four environmental factors on the recruitment of cyanobacteria from bottom sediments in the eutrophic Shanzi Reservoir. Temperature and light were identified as the key determinants for the recruitment of Microcystis and Oscillatoria. Cyanobacteria became dominant at higher temperature (20 °C) and light intensity (2000 lx) and Microcystis and Oscillatoria were the major species. Detailed recruitment simulation undertaken with the respective gradients of temperature and light suggested that both Microcystis and Oscillatoria are temperature sensitive and that their critical temperature point was 10 °C. However, distinct light impacts were observed only on Microcystis. The recruitment of Oscillatoria was light independent, whereas Microcystis had a positive relationship with light intensity. Physical disturbance promoted Microcystis recruitment and also affected the structure of the recruited cyanobacterial community at the water-sediment interface, based on quantitative polymerase chain reaction (qPCR) and phylogenetic analysis.

The Presence of Toxic and Non-Toxic Cyanobacteria in the Sediments of the Limpopo River Basin: Implications for Human Health

“…The study revealed that 99% of South Africa’s major impoundments contained toxicogenic strains of Microcystis . The study by Su et al [ 58 ] in the Shanzi impoundment, China showed that the sediments were the source of cyanobacteria inoculum. This implies that the cyanobacteria flocculates in the sediments during periods of adverse environmental conditions, such as cessation in river flows.…”

“…The cyanobacteria cysts and spores are related to the summer environmental conditions in the Limpopo river basin, where the majority of tributaries are perennial and river flows commence during the period of summer rainfall. The river flows disturb the sediments, thus bringing into the water column the cyanobacteria cysts or spores [ 58 ]. The source of nutrients in the Limpopo river basin may be attributed directly to sewage discharge of municipal waste water plants such as Glen Valley and Mahalpye on the Botswana side, and on the South Africa side, the western and northern parts of the city of Johannesburg to the town of Musina and indirectly to the agricultural practices of fertilizer application and animal waste [ 46 , 48 , 49 , 50 , 51 , 52 ].…”

Spatio-Temporal Variations in Phytoplankton Communities in Sediment and Surface Water as Reservoir Drawdown—A Case Study of Pengxi River in Three Gorges Reservoir, China

“…However, the seed bank in lakes cannot be brought in or out. In addition, the hydrological and hydrodynamic conditions of a reservoir significantly affect their germination, vertical migration, recruitment, and the forming of algal blooms [18,31].…”

“…The number of reservoirs in the world is increasing, and most large-and medium-sized rivers have become cascade reservoirs. Reservoirs are one of the most important components of freshwater ecosystems; however, researches on the resting stages of phytoplankton have been mainly conducted in shallow lakes and littoral sea area, while studies on reservoirs are scarce [30,31].…”