Does the Kis-Balaton Water Protection System (KBWPS) Effectively Safeguard Lake Balaton from Toxic Cyanobacterial Blooms?

Responses of RTgill-W1 cells to cyanobacterial metabolites microcystin-LR, anabaenopeptin-A, cylindrospermopsin, their binary and ternary mixtures

The aim of our study was to investigate the effects of cyanobacterial metabolites: microcystin-LR (MC-LR) anabaenopeptin-A (ANA-A), cylindrospermopsin (CYL), their binary and ternary mixtures on rainbow trout (Oncorhynchus mykiss) gill (RTgill-W1) cell line. We determined the following cell parameters: Hoechst and propidium iodide (PI) double staining, intracellular ATP level with luminometric assay, glutathione level with ThiolTracker Violet®- glutathione detection reagent and cytoskeletal F-actin fluorescence. The results showed that although reduction of Hoechst fluorescence was observed in both binary and ternary combinations of cyanobacterial metabolites, the mixture of MC-LR + ANA-A + CYL was the most potent inhibitor (EC50 = 148 nM). PI fluorescence and ATP levels were more increased in the cells exposed to the mixtures than those exposed to the individual metabolites with synergistic toxic changes suggesting apoptosis as the mechanism of cell death. Reduced glutathione level was also decreased in cells exposed both to single metabolites and their mixtures with the highest decrease and synergistic effects at 334 nM MC-LR+334 nM ANA-A+ 334 nM CYL suggesting induction oxidative stress by the tested compounds. Reduction of F-actin fluorescence was found in the cells from all of the groups exposed to individual metabolites and their mixtures, however the highest level of inhibition showed the binary MC-LR + CYL and the ternary MC-LR + ANA-A + CYL with synergistic interactions. The study suggests that in natural conditions fish gill cells may be very sensitive to individual cyanobacterial metabolites and more prone to their binary and ternary mixtures.

[Long-term low-dose microcystin-LR exposure induces renal injury in mice by activating PI3K/AKT signaling pathway]

OBJECTIVE

To investigate the toxic effect of long-term low-dose exposure to microcystin-LR (MC-LR) on kidney and its underlying molecular mechanism.

METHODS

Forty male C57BL/6 mice were randomized into 4 groups for exposure to 0, 1, 60, and 120 μg/L MC-LR (mixed in drinking water) for 12 months, and the body and kidney weight changes and renal pathologies of the mice were observed. The renal function indexes, the mRNA expression levels of IL-6, TNF-α and IL-10, and relative expression levels of PI3K/AKT pathway proteins in the kidney of the mice were detected. These parameters were also detected in HEK293 cells treated with MC- LR, LY294002, or both.

RESULTS

The overall trend of body weight changes was consistent among the 4 groups of mice, and their kidney mass and kidney index underwent no significant changes. In mice exposed to 60 and 120 μg/L MC-LR, obvious renal structural damage and significant elevation of the BUN and SCr levels were observed (P < 0.05) with up-regulated levels of IL-6 and TNF-α mRNA and increased protein expressions of p-PI3K/PI3K and p-AKT/AKT in the renal tissues (P < 0.05). IL-10 mRNA expression was significantly decreased in all the exposure groups (P < 0.05). The levels of BUN and Cr increased significantly in MC-LR-treated HEK293 cells and decreased in cells treated with both MC-LR and LY294002 (P < 0.05). The mRNA expression levels of IL-6 and TNF-α increased and the level of IL-10 mRNA decreased obviously in MC-LR-treated cells, and the opposite changes were observed in the cells with the combined treatment (P < 0.05). The proteins levels of p-PI3K/PI3K and p-AKT/AKT were significantly up-regulated in MC-LR group and down-regulated in the combined treatment group (P < 0.05).

CONCLUSION

MC- LR can activate inflammatory response and induce renal structural and functional damages in mice by activating the PI3K/AKT signaling pathway.

Joint Spatial Modeling of Nutrients and Their Ratio in the Sediments of Lake Balaton (Hungary): A Multivariate Geostatistical Approach

Eutrophication, water quality, and environmental status of lakes is a global issue that depends not only on external loadings from industrial, agricultural, and municipal sources but often also on internal loadings from lake sediments. In the latter case, in addition to the quality and quantity of nutrients stored in sediments, their relative content may be an important factor. In the example of Lake Balaton, we jointly modeled the spatial distribution of the nutrients nitrogen (N) and phosphorus (P) and their ratio (i.e., N:P) in the sediments of the lake and then provided spatial predictions at different scales (i.e., point, basin, and entire lake) with the associated uncertainty. Our aim was to illustrate the merits of applying multivariate geostatistics when spatial modeling of more than one variable is targeted at various scales in water ecosystems. Variography confirmed that there is a spatial interdependence between the nutrients. The results revealed that multivariate geostatistics allows this interdependence to be taken into account and exploited to provide coherent and accurate spatial models. Additionally, stochastic realizations, reproducing the joint spatial variability, can be generated that allow providing spatially aggregated predictions with the associated uncertainty at various scales. Our study highlighted that it is worthy of applying multivariate geostatistics in case spatial modeling of two or more variables, which jointly vary in space, is targeted in water ecosystems.

Cyanobacteria, cyanotoxins, and their histopathological effects on fish tissues in Fehérvárcsurgó reservoir, Hungary

Cyanobacteria are important members of lake plankton, but they have the ability to form blooms and produce cyanotoxins and thus cause a number of adverse effects. Freshwater ecosystems around the world have been investigated for the distribution of cyanobacteria and their toxins and the effects they have on the ecosystems. Similar research was performed on the Fehérvárcsurgó reservoir in Hungary during 2018. Cyanobacteria were present and blooming, and the highest abundance was recorded in July (2,822,000 cells/mL). The species present were Aphanizomenon flos-aquae, Microcystis flos-aquae, Microcystis wesenbergii, Cuspidothrix issatschenkoi, Dolichospermum flos-aquae, and Snowella litoralis. In July and September, the microcystin encoding gene mcyE and the saxitoxin encoding gene sxtG were amplified in the biomass samples. While a low concentration of microcystin-RR was found in one water sample from July, analyses of Abramis brama and Carassius gibelio caught from the reservoir did not show the presence of the investigated microcystins in the fish tissue. However, several histopathological changes, predominantly in gills and kidneys, were observed in the fish, and the damage was more severe during May and especially July, which coincides with the increase in cyanobacterial biomass during the summer months. Cyanobacteria may thus have adverse effects in this ecosystem.