The effects of water-level changes on periphytic algal assemblages in Poyang Lake

Abstract

Poyang Lake, which is the largest freshwater lake in China, has a seasonal flooding cycle that significantlychanges the water level every year. The aim of this study was to research the effects of water-level changeson periphytic algal assemblages in Poyang Lake. Dynamic shift of periphytic algal biomass were studied fromNovember 2016 to July 2019. Periphytic algal biomass and species composition were analyzed microscopically, andphysicochemical conditions were measured. There were significant seasonal variations in the community distributionof periphytic algae. The biomass of the periphyton ranged from 8 to 22,636 mg m-2. Periphytic algal biomassranged from 30 to 622 mg m-2 with the average of 204 mg m-2 in the LWL phase; periphytic algal biomass rangedfrom 8 to 21,839 mg m-2, with the average of 3,399 mg m-2 in the IWL phase. It ranged from 166 to 22,636 mgm-2, with the average 4,320 mg m-2 in the HWL phase and from 16 to 3,231 mg m-2 with the average of 585 mgm-2 in the DWL phase. There were temporal variations in periphytic algal community structure in Poyang Lake.Cryptophyceae dominated in algal periphyton from November 2016 to February 2017. Bacillariophyceae dominatedfrom March to July 2017 (increasing water-level phases). Pyrrophyceae and Euglenophyceae were dominant fromAugust and September (high-water-level phase) in 2017. Bacillariophyceae dominated through 2018 with occasionaldominance of Cryptophyceae from January to June and the occasional dominance of Chlorophyceae fromJuly to December. Chlorophyceae dominated from January to July in 2019 with occasional dominance of Bacillariophyceae.The water-level variations led to environmental heterogeneity in Poyang Lake, creating heterogeneoushabitats for algal periphyton. Our study revealed the primary importance of water level, water temperature, conductivity,total nitrogen, nitrite and total phosphorus as abiotic local factors structuring the periphytic algal communityin Poyang Lake. The water-level changes did not prevent growth of periphytic algae, but it did change the periphyticalgal community assemblages. This research provides data on the periphytic algae in Poyang Lake and will beuseful for establishing biological indicators of environmental changes and protecting Poyang Lake in the future.

Environmental Drivers and Aquatic Ecosystem Assessment of Periphytic Algae at Inflow Rivers in Six Lakes over the Yangtze River Basin

“…The periphytic algae in the Weihe river basin were examined by Liu et al, who discovered that Bacillariophyta is the dominant phylum [35]. Chlorophyta, Bacillariophyta, and Cyanobacteria were the most common periphytic algae in Poyanghu Lake [11]. Bacillariophyta was likewise found to be the most prevalent species in the Danjiangkou Reservoir and its associated water channel [10].…”

“…Seasonal fluctuation had a substantial impact on environmental parameters at the Danjiangkou Reservoir and its related water diversion channel, water temperature and nutrient concentration were the key factors determining the structure of the periphytic algae community [9], and the environmental factors plays an important role in shaping the periphytic algal community assembly in the water diversion channel based on marker gene analysis [10]. Different water levels in Poyang Lake resulted in environmental variety, resulting in varied habitats for periphytic algae [11]. Periphytic algae in Lake Taihu had a distinct community composition, with spatial variation and nutrient concentrations [12].…”