Extreme weather event may induce Microcystis blooms in the Qiantang River, Southeast China

Abstract

A severe cyanobacterial bloom in the mainstem of a large Chinese river was first reported from China. The Qiantang River is the longest river in the Zhejiang province, southeast China. It provides drinking water supply to ~ 16 million people, including Hangzhou city. Fifteen sites along the Qiantang River (including upper, middle (Fuchunjiang Reservoir), and lower reaches and tributaries) were sampled between August 13 and September 9, 2016 to conduct a preliminary examination of the outbreak of Microcystis blooms. Laboratory investigation revealed that Microcystis spp. are dominant in the Fuchunjiang Reservoir (an overflow reservoir on the mainstem of the Qiantang River) with an extremely high cell density of 2.3 × 10 cells/L, leading to a severe bloom in the mainstem of the Qiantang River. Investigations of the meteorological, hydrological, and nutrient characteristics associated with the bloom indicated that extremely dry (6.8 mm rainfall from August 13 to September 9, 2016) and hot (32 consecutive days of temperatures > 30 °C from July 20 to August 31, 2016) weather might be the key factors triggering the bloom. Additionally, the extremely low flow of the tributary, Lanjiang River (142 ± 56 m/s from August 13 to September 9), and its high nutrient background, favored the bloom. While nutrient reductions are important, the most immediate and effective management approach might be to implement appropriate minimal flow conditions to mitigate the blooms.

Long-Term Spatial and Temporal Monitoring of Cyanobacteria Blooms Using MODIS on Google Earth Engine: A Case Study in Taihu Lake

“…Wind speed affects FA max more than FA mean because wind helps cyanobacteria to form surface scum [15], especially when the wind speed is less than 4 m/s [61]. However, annual environmental variables have different effects; water quality factors, especially nutrient loadings (TN and TP)) were positively correlated with annual cyanobacteria blooms (Figure 17), probably because sporadic cyanobacteria blooms are affected by meteorological factors to a large extent, e.g., wind speed, wind direction, and temperature, but frequent and large-scale cyanobacteria blooms from the interannual perspective are dominated by nutrient distribution and abundance [7,26,62,63]. Meteorological factors were thought to play a more important role in cyanobacteria bloom formation, especially when Taihu Lake's nutrient loadings were sufficient [64,65].…”

Effect of Dilution on the Pollutant Monitoring in Decentralised Treatment Facilities Using Electrical Conductivity Sensors: Experimental and Modelling Insights

“…The pollutant concentration in the background water is much lower than that in initial sewage. In addition, the TP concentration in plain and mountainous areas were randomly distributed in the range of 0.2-0.3 and 0.1-0.2 mg/L during dilution, respectively (Guo et al 2018). The corresponding electrical conductivities of background water were set randomly from 150-400 and 30-60 μS/cm.…”

Precipitation mediate the distribution of phytoplankton communities in a tributary of Three Gorges Reservoir

“…The effects of precipitation on freshwater ecosystems have received increasing attention in recent decades, because extreme precipitation events are predicted to increase due to climate change in the near future (IPCC, 2013), and more extreme precipitation events are now being observed globally (Lehmann et al, 2015;Richardson et al, 2019). Freshwater ecosystems in China are directly in uenced by the East Asian monsoon which drives concentrated precipitation spikes in summer, andmight play a key role in in uencing water quality and aquatic biota (Guo et al, 2018). Some studies have examined the relationship between precipitation and phytoplankton (Ahn et al, 2002a;Richardson et al, 2019;Sung-Su-Hong et al, 2002;Wu et al, 2013;Zhou et al, 2012), and precipitation and water quality (Jeong et al, 2011).…”