Tracing the fate of microcystins from irrigation water to food chains: Studies with Fragaria vulgaris and Meriones shawi

Abstract

Microcystins (MCs) are cyanobacterial toxins that can negatively impact human and animal health. This study investigated the bioaccumulation, transfer, depuration, and health risks of MCs in strawberry plants (Fragaria vulgaris) and Meriones shawi animals. The plants were irrigated with 1, 5, 10, and 20 μg/L MCs for 60 days (bioaccumulation phase) and then with clean water for 30 days (depuration phase). The harvested plants (roots and leaves) were then prepared in an aliquot form and used as feed for Meriones shawi. Liquid chromatography-mass spectrometry (LC/MS/MS) was used to measure MC concentrations in plant and animal tissues. The bioaccumulation of MCs was found to be highest in the roots, followed by leaves, fruits, liver, stomach, and fecal matter. The bioaccumulation factor (BAF) was highest in perlite (8.48), followed by roots (5.01), leaves (1.55), stomach (0.87), and fecal matter (1.18), indicating that the parts with high bioaccumulation factor had high translocation of MCs. The transfer of MCs to animal organs was low, and the daily toxin intake of adult consumers of strawberry fruit irrigated with 1, 5, 10, and 20 μg/L MC did not exceed the WHO-recommended limit of 0.04 μg MC-LR/Kg of bw/day. However, fruits from plants irrigated with 10 and 20 μg/L may pose a moderate health risk to children (25 Kg bw), and Meriones' consumption of leaves may pose a significant health risk. After the depuration phase, MC concentration in perlite, roots, leaves, and fruits decreased, indicating that depuration reduced the danger of MC transmission and bioaccumulation. The study also found that glutathione reductase and glutathione S-transferase activity were essential in the depuration of MCs in the tested plants. The findings suggest that legislation regulating the quality of irrigation water in terms of MC concentrations is necessary to prevent detrimental consequences to crops and human exposure.

Keywords: Bioaccumulation; Cyanobacteria; Depuration; Fragaria vulgaris; Health risks; Meriones shawi and microcystins; Transfer.