Microcystis toxigenic strains in urban lakes: a case of study in Mexico City

Abstract

Microcystis is a bloom-forming, common cyanobacterium in urban lakes of Mexico City. To assess the presence of potentially cyanotoxin-producing Microcystis, molecular techniques were applied and acute toxicity bioassays were performed with Daphnia magna neonates exposed to cyanobacterial crude extracts. Toxigenic potential of isolated strains was inferred by amplifying the mcyA-Cd genes and their identity as Microcystis was confirmed through the 16S rDNA and phycocyanin operon amplification. Microcystins synthesized under culture conditions were quantified through ELISA. The acute toxicity bioassays revealed that mortality was independent from the cyanotoxin concentration in some strains; this suggests the presence of other metabolites (different from microcystins) that also exerted an important biological effect. Isolated strains had the mcyA-Cd gene and most of them produced variable amounts of microcystins in the culture conditions used, confirming their toxigenic potential. Results warn about possible toxic effect risks for aquatic biota, neighboring areas, visitors and users of these sites, due to the constant presence of these blooms in the studied water bodies.

Bioaccumulation of microcystins by fish associated with a persistent cyanobacterial bloom in Lago de Patzcuaro (Michoacan, Mexico)

“…Only recently, however, have MCYSTs been identified in Mexican freshwater systems. In addition to a previous report in the scientific literature of MC‐LR 31 in a reservoir in Valle de Bravo, two very recent studies 32, 33 have identified MCYSTs or MCYST‐producing strains of Microcystis in several such systems, including natural and urban lakes, additional reservoirs, and channels. Concentrations of particulate MCYST in Lago de Patzcuaro are low to intermediate to levels found in other freshwater systems, and lower than levels measured in other Mexican lakes.…”

Biomarkers involved in energy metabolism and oxidative stress response in the liver ofGoodea gracilisHubbs and Turner, 1939 exposed to the microcystin-producingMicrocystis aeruginosaLB85 strain

“…G. gracilis is a filter feeder and omnivorous fish that lives in remnant water bodies of Central Mexico that sustain contamination with large amounts of nutrients and organic matter. Recent studies report high concentrations of MCs in lakes in Chapultepec Park, in addition to diverse strains that produce these cyanotoxins (Arzate‐Cárdenas et al, ). In view of the threatened status of this species and the lack of information on permissible levels of MCs in freshwater systems in Mexico, the present study assessed PP activity; LDH and ADH metabolism; ROS formation , H 2 O 2 ); oxidative stress measured as thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (ROOHs) and protein oxidation (RCO); and antioxidant defense as determined by the activity of the enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), in the livers of G. gracilis exposed to different cell densities of the MC‐producing strain Microcystis aeruginosa LB85 under laboratory conditions.…”

Seasonal variation of <em>Microcystis aeruginosa</em> and factors related to blooms in a deep warm monomictic lake in Mexico

“…Later, blooms were reported in the Valle de Bravo reservoir (Ramírez García et al, 2002) and a eutrophic crater lake in Los Tuxtlas (Vázquez et al, 2005); in both cases, blooms were recorded in spring and summer, with a decline in biomass in surface waters during winter. The occurrence of microcystins in eutrophic reservoirs and urban lakes in Mexico has also been reported, with microcystins concentrations exceeding the WHO recommended limit (1 µg L -1 ) (Arzate-Cárdenas et al, 2010;Vasconcelos et al, 2010;Pineda-Mendoza et al, 2012); M. aeruginosa and other Microcystis species dominated the phytoplankton community of these reservoirs and urban lakes. Therefore, monitoring the presence and abundance of M. aeruginosa in lakes and reservoirs in Mexico from which the water is used for agricultural, recreational and human consumption purposes is crucial to avoid health risks, especially if these waterbodies are prone to eutrophication.…”

“…A high incidence of cyanobacterial blooms has been observed in tropical regions of Africa, America, Asia and Australia (Frias et al, 2006;Haande et al, 2007;Arzate-Cárdenas et al, 2010;Mowe et al, 2014;Ninio et al, 2020). In Mexico, the dominance of M. aeruginosa was reported for the first time in an artificial reservoir of Mexico City (Alcocer et al, 1998), and Lake Atezca, a subtropical monomictic lake (Dıáz-Pardo et al, 1998).…”