[Seasonal variations and driving factors of phytoplankton community shift in Datun Lake with long-term stress of arsenic contamination.] / é•¿æœŸç ·èƒè¿«ä¸‹å¤§å±¯æµ·æµ®æ¸¸æ¤ç‰©ç¾¤è½çš„å­£èŠ‚æ€§ç‰¹å¾åŠå ¶é©±åŠ¨å› å­.

Heavy metal is an important environmental stress that threatens water quality and ecological health of surface waters. Therefore, it is vital to identify the responses of lake community to long-term pollution for sustainable ecological restoration of polluted lakes. From June 2017 to March 2018, we conducted a seasonal survey of phytoplankton and environmental factors in Datun Lake, which had a decadal history of tailing-related arsenic contamination. Consistent with results from previous studies, phytoplankton were dominated by As-tolerant taxa such as Cyanophyta. Results of the analysis of similarities and analysis of variance showed that there were significant temporal variations in phytoplankton community structure and biomass, but without spatial variation. Results of the Pearson correlation analysis demonstrated that the total phytoplankton biomass was positively related to lake-water soluble orthophosphate and arsenic, which was consistent with the differential effect of arsenic on algae growth (e.g. promotion at low concentration and suppression at high concentration). The increases of phosphate might alleviate the toxic impacts of arsenic on phytoplankton. Redundancy analysis showed that the soluble nutrients and arsenic were significant factors driving phytoplankton community variations. The results of variation partitioning demonstrated that nutrients and water temperature explained 17.6% and 3.8% of community variations, respectively, with strong interaction with arsenic (15.1%). Arsenic did not affect phytoplankton community assembly, indicating that the dominant algae were tolerant to arsenic and thus highly insensitive to the arsenic stress. Therefore, the seasonal variations of phytoplankton dominated by As-tolerant algae in Datun demonstrated that the low-As promotion effect on phytoplankton should be considered in ecological restoration of polluted lakes.

[Identification of the long-term patterns of catchment development and diatom community changes in Xihu Lake, Dali, Yunnan, China]. / å¤§ç†è¥¿æ¹–æµåŸŸå¼€å‘åŽ†å²ä¸Žç¡ è—»ç¾¤è½å˜åŒ–çš„æ¨¡å¼è¯†åˆ«.

Limnological studies have long focused on the nine largest plateau lakes and ecological assessment of lake eutrophication in Yunnan. However, comprehensive surveys of small and me-dium-sized lakes and their response to multiple stressors are largely absent. Here, we combined multi-proxy sediment analyses and documentary data, aiming to identify the long-term pattern of diatom community changes under the influence of climate change and anthropogenic disturbances, and to quantify their driving strengths. The results showed that Xihu Lake was in a pre-impact state with little ecological variability before the 1950s. Thereafter, expansion of land use increased the nutrient input and altered the lake hydrology, resulting in a significant shift of dominant diatoms from Cocconeis placentula to Fragilaria spp. From 1997, accelerating nutrient enrichment and hydrological changes led to the replacement of benthic diatoms by planktonic ones, resulting in a consistent loss of macrophytes and a decrease of ecological stability. Therefore, the types and strength of catchment development should be fully evaluated for effective protection of small and medium-sized alpine lakes in the context of global warming.