Sampling and environmental parameters
The
study area was located in the Fenhe River of Shanxi province, northern
China (latitude 35°–39° N; longitude 110°–114° E) (Fig. 1).
We collected 144 samples from
January 2019 to December 2019 at 6 sampling stations. A 2 L sampler was
used to collect water samples at the depth of 0.5 m, then filtered
through 0.22 μm mixed fiber microporous membranes. And the fraction
>0.22 μm was used for
DNA extraction, the corresponding water samples were used to determine
the physical and chemical parameters. The nitrate
(NO3−), nitrite
(NO2−), and phosphate
(PO43−) were measured following the
methods in Wang, Lou, Sun, and Song (2008). The dissolved organic carbon
(DOC) concentration was determined according to the method described by
Bolan, Baskaran, and Thiagarajan (1996). The Water and Wastewater
Monitoring Analysis Method was used to measure Chlorophyll a (Chl a)
concentrations (Zhu et al., 2019).