Predicting the effects of reservoir impoundment on phytoplankton and shoreline vegetation communities using the space-time substitution method

Abstract

The prediction of the influence of reservoir impoundment on water quality and phytoplankton community is the basis of ecological compensation or restoration. The aim of the current study was to predict the effects of reservoir impoundment on phytoplankton and shoreline vegetation communities using the space-time substitution method. The Huangjinxia Reservoir under construction on the Han River was selected as the research object. The space-time substitution method indicated that the average values of the total phosphorus (TP) and ammonia (NH4+-N) increased from 0.049 and 0.279 mg L−1 to 0.139 and 1.132 mg L−1, respectively, after reservoir impoundment. The percentage of diatom biomass exceeded 95% before the reservoir impoundment. However, it was gradually decreased to 75% after the reservoir impoundment. Meanwhile, the biomass of Chlorophyta, Cryptophyta and Pyrrophyta increased significantly, accounting for 32, 20 and 13% of the total biomass, respectively, after reservoir impoundment. Cynodon dactylon (65.3%), Polygonum hydropiper (51.7%) and Aster subulatus (50.3%) were the dominant shoreline vegetation before the reservoir impoundment, whereas after the reservoir impoundment, the dominant species shifted to Alternanthera philoxeroides (62.3%), Lobelia chinensis (55.7%) and C. dactylon (53.9%). Our results suggested that the percentage of bloom-forming phytoplankton would gradually increase after the reservoir impoundment. In addition, A. philoxeroides, C. dactylon and L. chinensis would be the plants suitable for living in the shoreline of reservoirs in this area.

Different tolerance of three typical riparian plants (Cynodon dactylon, Alternanthera philoxeroides, and Acorus calamus) to different depths of waterlogging caused variations in soil nutrient release and microbial diversity

“…In our preliminary field investigation, we found that the dominant plants around the study area were C. dactylon, A. philoxeroides, and Acorus calamus (Jian et al 2018). This finding was the same as that in some locations in the TGR (Xu et al 2021). Differently, previous researchers focused on the effect of plants on soil nutrients in the case of inundation at a depth of ten or even tens of meters.…”

“…This study selected three plants, including C. dactylon (CD), A. philoxeroides (AP), and Acorus calamus (AC), which were dominated in the WLFZ of the Shiquan Reservoir on the Han River (Xu et al 2021). Planting containers was the 50 Â 100 Â 72 cm boxes, of which had 25 kg soils, ensuring that the soil was about 30 cm in thickness and evenly distributed.…”

“…This process promoted the release of nutrients such as N, P, and organic matter, which were partly supposed to be absorbed by the soil (Wang et al 2020;Chen et al 2021). Moreover, during the operation of the reservoir, the plant community would be reverse succession towards flood-tolerant herbaceous plants, such as Cynodon dactylon, Alternanthera philoxeroides, Acorus calamus, and other hygrophytes (Xu et al 2021). As illustrated by many field surveys and laboratory simulations, these dominant plants in the WLFZ would die or rebirth in response to changes in the water level, with a continuous effect on soil physical-chemical properties in both the WLFZ and overlying water at certain time scales (Liu et al 2017a(Liu et al , 2017bGe et al 2021).…”