Cyanobacterial dynamics and toxins concentrations in Lake Alto Flumendosa, Sardinia, Italy

Abstract

Seasonal blooms of cyanobacteria (CB) are a typical feature of Lake Alto Flumendosa (Sardinia, Italy). The waters of this lake are used for drinking water supply, for agricultural and industrial uses, and fish farming activities. Since cyanotoxins are not monitored in edible organisms, diet could be a relevant route of human exposure. CB also represent a threat for the health of wild and domestic animals that use lake water for beverage. Therefore, to characterize the CB community and assess the risk for human and animal population, CB dynamic, mcyB+ fraction, and microcystins (MCs) concentration have been followed monthly for 18 months, in three stations. Results confirmed the presence of several toxigenic species. Planktothrix rubescens dominated between August 2011 and April 2012 (3.5×106 cells L-1), alternating with Woronichinia naegeliana (8×106 cells L-1) and Microcystis botrys (9×105 cells L-1). Dolichospermum planctonicum was always present at low densities (104 cells L-1). MCs were detected, at values well below the 1 µg L-1 threshold of WHO for drinking water. The molecular analysis of mcyB gene for P. rubescens indicated the presence of a persistent toxic population (average 0.45 mcyB/16S rDNA). Highly significant linear regressions were found between P. rubescens and the sum of the demethylated MC variants, and between M. botrys and the sum of MC-LR and MC-LA, also when co-occurring, suggesting that these two species were responsible for different MC patterns production. The regression lines indicated a quite stable MC cell quota. However, in some spotted samples very different values were obtained for both MC concentrations and cell quota (from 10-fold lower to 30-40-fold higher than the ‘average’) showing an unexpected significant variability in the rate of toxin production. The relatively low cell densities during the monitoring period is consistent with the low-to absent MC contamination level found in trout muscle; however, the analytical method was affected by low recovery, probably due to MC-protein binding. Our results show that, during the study period, no risk of exposure for the human and animal population occurred. However, the persistence of a complex CB community characterised by a significant toxic fraction suggests the need for periodic monitoring activity. Particularly, the hidden deep summer P. rubescens blooms, located where water is taken for drinking water supply, and M. botrys, able to produce the most toxic MC variants with high cell quota, should be kept under control. The documentation and interpretation of sudden changes in toxins concentrations deserve special attention. This is particularly relevant in proximity of fish farming plants and water catchment sites.

[RETRACTED] Short-term dynamics and growth parameters of cyanobacteria and microcystins in freshwater from the Sidi-Yacoub dam, North-east of Algeria

“…The quantification of microcystin concentrations is performed on triplicate aliquots of each water sample and analyzed using the PP2A inhibition assay with a commercial ELISA kit (Envirologix Inc., USA; lower limit of detection: 0.1 μg/L) following the manufacturer's recommendations. After three freeze-thaw cycles, total microcystins (MCT) are quantified in water samples to lyse cyanobacteria cells and release toxins (Stefanelli et al 2017). Meanwhile, the dissolved fraction of microcystins in water (MCD) is quantified on pre-filtered water samples through a 0.45μm porosity membrane.…”

Cyanobacteria Dynamics in a Mediterranean Reservoir of the North East of Algeria: Vertical and Seasonal Variability

“…In Zit Emba, Dolichospermum showed a strong presence in summer and autumn; which was not surprising in the warmest season, as this genus prefers high summer temperatures and high water stability [Marchetto et al, 2009], with an extended distribution in areas with a temperate climate [Mariani et al, 2015;Padedda et al,2017;Stefanelli et al, 2017].…”

“…These genera were reported to be the main CyanoHAB producers in the Mediterranean in the summer-autumn period [Carrasco et al, 2006]. In the Lake Alto Flumendosa of Sardinia, Planktothrix rubescens dominated between August 2011 and April 2012, alternating with Woronichinia naegeliana and Microcystis botrys; Dolichospermum planctonicum was always present at low densities [Stefanelli et al, 2017]. Nevertheless, the other genera, including oscillatoria, Merismopedia and Spirulina represent a small proportion of the total cyanobacterial community in the Zit-Emba reservoir.…”

Remediation Strategies to Control Toxic Cyanobacterial Blooms: Effects of Macrophyte Aqueous Extracts on Microcystis aeruginosa (Growth, Toxin Production and Oxidative Stress Response) and on Bacterial Ectoenzymatic Activities

“…The most efficient aqueous extract was also tested very preliminarily on the growth and toxicity of three filamentous cyanobacterial monoclonal non axenic strains: Planktothrix rubescens isolated from Flumendosa Lake, strain F10 (Italy [ 38 ]), MC producing, and two ANACC (Australian National Algae Culture Collection; CSIRO Tasmania) reference strains, CS1101 Raphidiopsis raciborskii and CS1034 Chrysosporum ovalisporum , both cylindrospermopsin producers [ 39 ].…”