The low TN:TP ratio, a cause or a result of Microcystis blooms?

The physicochemical parameters of water, the concentration of chlorophyll-a and the submerged aquatic vegetation (SAV) were studied to evaluate the effects of different winter seasons on the biomass of macrophytes in shallow eutrophic lakes. We hypothesised that a lack of ice cover or early ice-out can influence the physicochemical parameters of water and thus change the conditions for the development of phytoplankton and SAV. The studies were conducted in four lakes of the Western Polesie region in mid-eastern Poland after mild winters with early ice-out (MW, 2011 and 2014) and after cold winters with late ice-out (CW, 2010, 2012 and 2013). The concentrations of soluble and total nitrogen, chlorophyll-a and the TN:TP ratio in the lakes were considerably higher, whereas the concentration of soluble and total phosphorus and water transparency were significantly lower after the MW compared with after the CW. No differences were found in water temperature, reaction and electrolytic conductivity. Low water turbidity linked with low concentration of chlorophyll-a after the CW resulted in increased water transparency and the total biomass of the SAV. The negative effect of the MW on the macrophyte species was stronger on more sensitive species (Myriophyllum spicatum, Stratiotes aloides) compared with shade tolerant Ceratophyllum demersum. Our findings show that the ice cover phenology affected by climate warming can change the balance between phytoplankton and benthic vegetation in shallow eutrophic lakes, acting as a shift between clear and turbid water states. We speculate that various responses of macrophyte species to changes in the water quality after two winter seasons (CW and MW) could cause alterations in the vegetation biomass, particularly the expansion of shade tolerance and the decline of light-demanding species after a series of mild winters.

Download Full-text

Composition of the archaeal community involved in methane production during the decomposition of Microcystis blooms in the laboratory

Canadian Journal of Microbiology ◽

10.1139/w2012-097 ◽

2012 ◽

Vol 58 (10) ◽

pp. 1153-1158 ◽

Cited By ~ 7

Author(s):

Peng Xing ◽

Huabing Li ◽

Qing Liu ◽

Jiuwen Zheng

Keyword(s):

Lake Taihu ◽

Archaeal Community ◽

Oxygen Depletion ◽

16S Rrna Genes ◽

Rrna Genes ◽

Polymorphism Analysis ◽

Methanogenic Community ◽

Controlled Systems ◽

Microcystis Blooms ◽

Different Temperatures

We investigated the microbial processes involved in methane (CH4) production from Microcystis bloom scums at different temperatures. A Microcystis slurry was collected from Lake Taihu and incubated in airtight bottles at 15, 25, and 35 °C. The production of CH4 was monitored, and the emission rate was calculated. The dynamics of the methanogenic community were analyzed by terminal restriction fragment length polymorphism analysis of archaeal 16S rRNA genes. Phylogenetic information for the methanogens was obtained by cloning and sequencing selected samples. Significant CH4 emission from the Microcystis scums was delayed by approximately 12 days by the natural oxygen depletion process, and CH4 production was enhanced at higher temperatures. Phylogenetic analysis indicated that the archaeal community was composed of Methanomicrobiales, Methanobacteriaceae, and a novel cluster of Archaea. An apparent succession of the methanogenic community was demonstrated, with a predominance of Methanobacteriaceae at higher temperatures. Higher temperatures enhanced the methanogenic transformation of the Microcystis biomass and the phylogenetic dominance of hydrogenotrophic methanogens, suggesting that H2 and CO2 might be the primary substrates for CH4 production during Microcystis decomposition without the participation of lake sediment. This work provides insight into the microbial components involved in Microcystis biomass fermentation in controlled systems.

Download Full-text