Factors to Affect the Eutrophication and Phytoplankton Blooms in the Three Gorges Reservoir

Abstract

The phytoplankton blooms in the tributary bays have become the most serious environmental problem in Three Gorge Reservoir (TGR), China. In order to understand the mechanism of those phytoplankton blooms, the factors to affect the eutrophication and Phytoplankton blooms have been summarized. Generally, in lakes eutrophication is a natural evolutionary process, which is affected by light, temperature, nutrients, predation, migration and stratification. Recent decade's human activities played a role to promote this evolution but not to change the evolutionary direction. However, in the TGR, the changed hydrodynamics caused by the TGD are considered to be the most important triggers to the phytoplankton blooms, especially the longer residence time, thermal density currents and stratification.

Hypoxia and its feedback response to algal blooms and CH4 emissions in subtropical reservoirs

“…Since the impoundment of the TGR, algal blooms have occurred frequently in tributary bays (Stone, 2008;Yang et al, 2022). Accordingly, the dominant species of algal blooms in key tributaries evolved from channel-type algae dominated by Bacillariophyta and dinoflagellates in the early stage of impoundment to lake-type algae dominated by cyanobacteria and Chlorophyta (Liu et al, 2016;Yang et al, 2017;Yao et al, 2022). On the other hand, by comparing the results from different studies on the monitoring of DO in some tributary bays, we found that there was a clear decreasing trend of DO concentration in the water of the tributary bays of TGR in recent years.…”

“…The TGR, as China's largest strategic freshwater resource reservoir, has been the focus of many scholars studying water quality and algal blooms in its tributary bays after its impoundment (Liu et al, 2016;Yang et al, 2017;Yang et al, 2022). Previous monitoring results (Zhang et al, 2009) show that the DO concentration in the TGR is generally higher than 6 mg•L -1 , and there have been no occurrences of hypoxic or anaerobic conditions in the waters.…”

“…When the planktonic algae in a reservoir are dominated by cyanobacteria, the carbon cycle process in the reservoir is significantly enhanced (Xue et al, 2021). Recently, field monitoring has found that the dominant species of algal blooms in the TGR have gradually evolved from channel-type blooms such as Bacillariophyta and Dinophyta blooms in the early stage of reservoir storage to lake-type blooms dominated by cyanobacteria and Chlorophyta (Liu et al, 2016;Yang et al, 2017). Additional research is needed to determine whether this succession process, with cyanobacteria as the dominant species in algal blooms, is an important factor in promoting hypoxia in tributary bays.…”