Abstract
Previous studies report significant changes on biotic communities caused by cascade reservoir construction. However, factors regulating the spatial–temporal plankton patterns in alpine cascade reservoir systems have not been fully explored. The current study explored effects of environmental factors on the longitudinal plankton patterns, through a 5-year-long study on the environmental factors and communities of phytoplankton and zooplankton in an alpine cascade reservoir system located upstream of Yellow River region. The findings showed that phytoplankton and zooplankton species numbers in the studied cascade reservoir system were mainly regulated by the hydrological regime, whereas nutrient conditions did not significantly affect the number of species. Abundance and biovolume of phytoplankton in cascade reservoirs were modulated by the hydrological regime and nutrient conditions. The drainage rate, N:P ratio, and sediment content in cascade reservoirs were negatively correlated with abundance and biovolume of phytoplankton. Abundance and biovolume of zooplankton were not significantly correlated with the hydrological regime but showed a strong positive correlation with nutrient conditions in cascade reservoirs. Shannon–Wiener index (H’) and the Pielou index (J) of phytoplankton were mainly regulated by the hydrological regime factors, such as drainage rate and sediment content in cascade reservoirs. However, temperature and nutrient conditions were the main factors that regulated the Shannon–Wiener index (H’) and the Pielou index (J) of zooplankton. Species number, abundance, and biovolume of phytoplankton showed a significant positive correlation with those of zooplankton. Hydrodynamics and nutrient conditions contributed differently in regulating community structure of phytoplankton or zooplankton. These findings provide an understanding of factors that modulate longitudinal plankton community patterns in cascade reservoir systems.
Highlights
Several dams are built on rivers worldwide to increase the use of water resources and meet surging domestic power demand (Graf, 1999; Finer and Jenkins, 2012; Grumbine and Pandit, 2013)
The findings showed that the Bacillariophyta–Chlorophyta pattern of phytoplankton composition did not change over time
The findings of this study showed that the environmental factors controlling species number, abundance, biovolume, and biodiversity of phytoplankton can be different in cascade reservoir systems
Summary
Several dams are built on rivers worldwide to increase the use of water resources and meet surging domestic power demand (Graf, 1999; Finer and Jenkins, 2012; Grumbine and Pandit, 2013). Several studies have explored the effects of cascade reservoirs on river ecosystems (Fan et al, 2015; Algarte et al, 2016; Wang Y. et al, 2016; Kang et al, 2017; Baumgartner et al, 2020). Studies report that cascade reservoirs cause significant changes in phytoplankton (Padisák et al, 2000; Silva et al, 2005; Wang et al, 2018), zooplankton (Hart, 2004; Perbiche-Neves and Nogueira, 2010; Okuku et al, 2016), benthic animals (Callisto et al, 2005), fish (Draštík et al, 2008), water physiochemical characteristics (Jorcin and Nogueira, 2005; Karnaukhova, 2007), and hydrological regimes (Matsuno et al, 2003) in river ecosystems. Studies on the effects of construction of cascade reservoirs on alpine river ecosystems are limited
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