Longitudinal Differences of Phytoplankton Community during a Period of Small Water Level Fluctuations in a Subtropical Reservoir Bay (Xiangxi Bay, Three Gorges Reservoir, China)

Abstract

The Three Gorges Reservoir (TGR) had a great inflow discharge with small water level fluctuations in the flood season of the year 2008, when a large-scale cyanobacterial bloom broke out in Xiangxi Bay (a tributary bay behaving like a lake) for the first time after the construction of the TGR impoundment. To compare spatiotem poral longitudinal differences of phytoplankton community structure during this period, weekly surveys were performed in Xiangxi Bay. The cyanobacterial bloom lasted from June 6 to July 18, 2008, with Microcystis aeruginosa as the dominant species. During this bloom the species diversity, evenness and community change rate was relatively low. The probable causes for the interruption of the bloom were precipitation and water temperature. In the non-cyanobacterial bloom period (July 25 to September 26, 2008) many other species dominated the community including Stephanodiscus hantzschii and Cryptomonas ovata, with higher values of species diversity, evenness and community change rate. As for the longitudinal differences, the community structure in the riverine zone was different from that in other zones, indicating the important effect of inflow from the upstream of Xiangxi Bay. The management actions in Xiangxi Bay should prevent blooms in the mainstream, lacustrine and transitional zone. IntroductionPhytoplankton composition can be recognized as a natural bioindicator because of its complex and rapid responses to fluctuations of environmental conditions (L IVINGSTON, 2001). Phytoplankton community composition changes as a consequence of species succession, which occurs in response to new environmental conditions (ÁLVAREZ-GÓNGORA and HERRE- RA-SILVEIRA, 2006). Two important factors appear to control the phytoplankton community structure, as well as the species succession. The first one is related to physical processes such as mixing conditions, light, temperature, turbulence, and salinity; and the second one is associated with nutrients (YUSOFF et al., 2002;NUCCIO et al., 2003;DOMINGUES et al., 2005;ÁLVAREZ-GÓNGORA and HERRERA-SILVEIRA, 2006;BROGUEIRA et al., 2007;DOMINGUES et al., 2007).

Responses of phytoplankton functional groups to the hydrologic regime in the Daning River, a tributary of Three Gorges Reservoir, China

“…The same result was also observed in the Xiangxi River, a tributary of TGR (Wang et al, 2011a). In the TGR, water flow was high during the flood season in the mainstream and tributary.…”

Phytoplankton functional groups response to environmental parameters in Muling River basin of northeast China

“…That could be the precipitation will bring external nutrients from the surrounding croplands into the river via the surface runoff lead to higher concentration. The same situations were also noticed in Yangtze River basin in the middle of China (Wang et al, 2011;Zhu et al, 2013). N:P ratio is also a crucial factor influencing phytoplankton growth and distribution (Lagus et al, 2004).…”

Spatial Biomass Production And Seasonal Nutrient Limitation Transitions In A Tributary of The Three Gorges Reservoir, China

“…Several previous studies in the tributary have evaluated the spatial analysis of biomass approximately 15 years ago e.g. spring bloom and nutrient limitation (Fang et al, 2013;Xu et al, 2009; Ye and Cai, 2009; Cai and Hu, 2006; Ye et al, 2006;Ye et al, 2007), the effect of Three Gorges Reservoir (TGR) impoundment and temporal coherence for water clarity (Bi et al, 2010;, the longitudinal difference in phytoplankton community structure (Wang et al, 2011a(Wang et al, , 2011b(Wang et al, , 2011c(Wang et al, , 2010dZeng et al, 2006), vertical mixing regimes and current characteristics (Liu et al, 2012;Yang et al, 2018), the sediment P-release (Fu et al, 2006;Zhijing et al, 2012), and XXB critical nutrient isotopes (Yang et al, 2015). However, these studies did not consider the trace metals interactions with the representative phytoplankton groups.…”