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Microcystins (MCs), natural hepatotoxic compounds produced by cyanobacteria, pose significant risks to water quality, ecosystem stability, and the well-being of animals, plants, and humans when present in elevated concentrations. The escalating contamination of irrigation water with MCs presents a growing threat to terrestrial plants. The customary practice of irrigating crops from local water sources, including lakes and ponds hosting cyanobacterial blooms, serves as a primary conduit for transferring these toxins. Due to their high chemical stability and low molecular weight, MCs have the potential to accumulate in various parts of plants, thereby increasing health hazards for consumers of agricultural products, which serve as the foundation of the Earth’s food chain. MCs can bioaccumulate, migrate, potentially biodegrade, and pose health hazards to humans within terrestrial food systems. This study highlights that MCs from irrigation water reservoirs can bioaccumulate and come into contact with plants, transferring into the food chain. Additionally, it investigates the natural mechanisms that organisms employ for conjugation and the microbial processes involved in MC degradation. To gain a comprehensive understanding of the role of MCs in the terrestrial food chain and to elucidate the specific health risks associated with consuming crops irrigated with water contaminated with these toxins, further research is necessary.

Over the last years, the use of artificial lakes and ponds to irrigate agricultural crops has been intensified and cultivation methods have been diversified. Hydroponics is a type of hydroculture which usually involves growing plants in an inert substrate, by using nutrient-enriched water to support plant growth. However, irrigating plants in hydroponic-based culture must be accompanied by monitoring the quality of irrigation water. The human health risks involved are mainly related to the proliferation of microcystin-producing cyanobacteria that contaminate water used for irrigation purposes. Strawberry (Fragaria vulgaris L.) is a widely cultivated plant of an increased economically importance worldwide. Its fruits provide essential elements for human nutrition; therefore, the study of its sensitivity to microcystins (MCs) is of paramount importance. The objective of this study was to evaluate the effects of MCs in irrigation water on the growth, physiology, and antioxidant defense system in F. vulgaris. In this study, strawberry seedlings at the three-leaf stage were grown in pots containing perlite under controlled conditions. Plants were exposed to a crude extract of Microcystis aeruginosa bloom at different concentrations of MCs (1, 5, 10, and 20 μg/L) for 60 days of exposure. The results showed that the highest concentrations of 10 and 20 μg/L induced a decrease in growth parameters. They resulted in root/shoot length decrease as well as number of leaves, roots/leaves dry and fresh weight. Furthermore, MCs reduced chlorophyll/carotenoid content, stomatal conductance, fluorescence, and total protein content of strawberry plants. At the same time, a significant increase in Malondialdehyde (MDA) (an indicator of lipid peroxidation), polyphenol, and sugar content were recorded in strawberry plants exposed to MCs at 5, 10, and 20 μg/L compared with the control. Additionally, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), Polyphenoloxydase (PPO), and ascorbate peroxidase (APX) activities significantly increased in plants under MCs exposure. The oxidative stress was higher in plants exposed to 10 and 20 μg/L of MCs from the second harvest (after 60 days of exposure) compared to those from the first harvest (after 30 days). Overall, the results obtained in this study indicate an increasingly negative effect of MCs on strawberry plants grown in hydroponics even at concentrations (10 and 20 µg/L). This effect is more damaging on the roots after exposure (60 days).

Microcystins (MCs) produced in eutrophic waters may decrease crop yield, enter food chains and threaten human and animal health. The main objective of this research was to highlight the role of rhizospheric soil microbiota to protect faba bean plants from MCs toxicity after chronic exposure. Faba bean seedlings were grown in pots containing agricultural soil, during 1 month under natural environmental conditions of Marrakech city in Morocco (March–April 2018) and exposed to cyanobacterial extracts containing up to 2.5 mg·L−1 of total MCs. Three independent exposure experiments were performed (a) agricultural soil was maintained intact “exposure experiment 1”; (b) agricultural soil was sterilized “exposure experiment 2”; (c) agricultural soil was sterilized and inoculated with the rhizobia strain Rhizobium leguminosarum RhOF34 “exposure experiment 3”. Overall, data showed evidence of an increased sensitivity of faba bean plants, grown in sterilized soil, to MCs in comparison to those grown in intact and inoculated soils. The study revealed the growth inhibition of plant shoots in both exposure experiments 2 and 3 when treated with 2.5 mg·L−1 of MCs. The results also showed that the estimated daily intake (EDI) of MCs, in sterilized soil, exceeded 2.18 and 1.16 times the reference concentrations (0.04 and 0.45 µg of microcysin-leucine arginine (MC-LR). Kg−1 DW) established for humans and cattle respectively, which raises concerns about human food chain contamination.

The application of natural compounds extracted from seaweeds is a promising eco-friendly alternative solution for harmful algae control in aquatic ecosystems. In the present study, the anti-cyanobacterial activity of three Moroccan marine macroalgae essential oils (EOs) was tested and evaluated on unicellular Microcystis aeruginosa cyanobacterium. Additionally, the possible anti-cyanobacterial response mechanisms were investigated by analyzing the antioxidant enzyme activities of M. aeruginosa cells. The results of EOs GC–MS analyses revealed a complex chemical composition, allowing the identification of 91 constituents. Palmitic acid, palmitoleic acid, and eicosapentaenoic acid were the most predominant compounds in Cystoseira tamariscifolia, Sargassum muticum, and Ulva lactuca EOs, respectively. The highest anti-cyanobacterial activity was recorded for Cystoseira tamariscifolia EO (ZI = 46.33 mm, MIC = 7.81 μg mL−1, and MBC = 15.62 μg mL−1). The growth, chlorophyll-a and protein content of the tested cyanobacteria were significantly reduced by C. tamariscifolia EO at both used concentrations (inhibition rate >67% during the 6 days test period in liquid media). Furthermore, oxidative stress caused by C. tamariscifolia EO on cyanobacterium cells showed an increase of the activities of superoxide dismutase (SOD) and catalase (CAT), and malondialdehyde (MDA) concentration was significantly elevated after 2 days of exposure. Overall, these experimental findings can open a promising new natural pathway based on the use of seaweed essential oils to the fight against potent toxic harmful cyanobacterial blooms (HCBs).