The Influence of a Eutrophic Lake to the River Downstream: Spatiotemporal Algal Composition Changes and the Driving Factors

Abstract

Algal blooms have been frequently found at the upper reaches of the Tanglang River, which is downstream from the eutrophic Dianchi Lake. The eutrophic lake upstream is considered to be a potential source of phytoplankton, which contributes to the development of harmful algal blooms in the river downstream and can cause many serious problems for the river ecology. However, few studies focused on these kinds of rivers. Therefore, a field observation and laboratory analysis were conducted in this study. The results showed that the Tanglang River was obviously spatially heterogeneous due to the eutrophic Dianchi Lake upstream. The toxic Microcystis from the Dianchi Lake dominated the phytoplankton at the upper reaches, but these were gradually, rather than immediately, replaced by centric diatoms and chlorococalean green algae in the middle and lower reaches. The results of correlation analysis indicated that the changes in hydrodynamic conditions and underwater light intensity accounted for the spatial variations. The differences in the adaptability of different algae to changing aquatic environments explained the spatial variations of phytoplankton abundance. The dominant algae, most of which was from the Dianchi Lake upstream, determined the characteristics of the total abundance at the Tanglang River. OPEN ACCESSWater 2015, 7 2185

Effects of Environmental Factors on the Temporal Stability of Phytoplankton Biomass in a Eutrophic Man-Made Lake

“…We observed that the variability of some environmental factors also had a significant influence on the temporal stability of phytoplankton ( Figure 7). The temporal stability of phytoplankton had a unimodal relationship with both NH 4 + -N and TP, a negative relationship with TN, and no relationship with WT, DO, and pH. The variability of these variables had little influence on the average total biomass of phytoplankton ( Figure 8).…”

“…There were significant differences of TN in the four seasons (one way ANOVA: F (3, 548) = 11.8, p < 0.001), with mean concentrations in the spring and winter being significantly higher than those in the summer and autumn (all p < 0.01 by post hoc Tukey HSD). Average values of NH 4 + -N ranged from 0.15 ± 0.07 mg/L in January 2013 to 3.24 ± 2.40 mg/L in December 2012. There were also apparent variations of NH 4 + -N in the four seasons (one way ANOVA: F (3, 548) = 8.9, p < 0.001), with mean concentrations in the winter and spring being significantly higher than those in the summer and autumn (all p < 0.05 by post hoc Tukey HSD).…”

“…Average values of NH 4 + -N ranged from 0.15 ± 0.07 mg/L in January 2013 to 3.24 ± 2.40 mg/L in December 2012. There were also apparent variations of NH 4 + -N in the four seasons (one way ANOVA: F (3, 548) = 8.9, p < 0.001), with mean concentrations in the winter and spring being significantly higher than those in the summer and autumn (all p < 0.05 by post hoc Tukey HSD). The mean concentrations of TP varied from 0.03 ± 0.04 mg/L in January 2013 to 1.01 ± 0.65 mg/L in July 2012 in the lake.…”

“…Phytoplankton is the most important primary producer in aquatic ecosystems and it is characterized by a short generation time and efficient trophic transfer, and is sensitive to the variations of environmental factors [1][2][3][4]. Recently, more and more lakes face eutrophication caused by human activities and global climate warming [5][6][7][8][9].…”

Controlling River Eutrophication under Conflicts of Interests—A GIS Modeling Approach

“…Large lakes and reservoirs represent a very important hydro-morphological modification factor inside a stream network in terms of nutrient balance and algal growth [21]. The large reservoirs situated in the mountainous upstream parts of both the Someşul Mic and Mare subcatchments were absent from these two alternatives.…”