Mercury biomagnification at higher rates than the global average in aquatic ecosystems of the Qinghai-Tibet Plateau

Mercury biomagnification in aquatic ecosystems is a global issue. Biomagnification patterns and drivers in alpine regions remain poorly understood. Hg biomagnification in the aquatic food web of the Qinghai-Tibetan Plateau (Q-T Plateau) was investigated. A total of 302 fish and macroinvertebrate tissue samples were analysed for total mercury (THg) and nitrogen (delta N-15) stable isotope ratios. Overall, 26.75% of fish individuals exceeded the USFWS consumption guidelines. A total of 52.17% of the sampling sites covering different habitats exhibited a significantly positive THg-delta N-15 relationship, which confirmed the Hg biomagnification potential of Q-T Plateau aquatic ecosystems. The Q-T Plateau Hg biomagnification rates were generally far higher than global averages regardless of the habitat type. Hg in sediments, elevation and population density were positively related to the Hg biomagnification magnitude on the Q-T Plateau, which could be attributed to the disproportionate response of Hg concentrations in macroinvertebrates and fishes along environmental gradients. Our findings offer empirical evidence that fish consumption on the Q-T Plateau poses a substantial Hg exposure risk to people living along river and lake shores. Higher biomagnification rates could further disproportionately accelerate Hg pollution in Q-T Plateau aquatic ecosystems under future anthropogenic activities and climate warming trajectories.

Automated summary

Mercury biomagnification in aquatic ecosystems, especially in alpine regions like the Qinghai-Tibetan Plateau, is poorly understood. This study investigates the biomagnification potential of mercury in the food web of the Q-T Plateau and finds that the mercury concentrations exceed consumption guidelines in 26.75% of fish samples. The biomagnification rates on the Q-T Plateau are generally higher than global averages and are positively correlated with sediment mercury, elevation, and population density.