Key Takeaways & Executive Findings
- •• • Sediment THg in ecological mariculture averaged 4.0 ± 1.3 ng·g−1 dw (n=56), indicating minimal Hg accumulation due to sandy/silty sediments and low inputs, which is critical for site selection and sediment management in sustainable aquaculture. • • Fish muscle THg and MeHg concentrations were 59.7 ± 30.0 and 53.8 ± 29.2 ng·g−1 ww (n=7), respectively, comparable to wild fish, demonstrating that ecological mariculture does not inherently reduce Hg bioaccumulation, necessitating food chain management. • • At high seafood consumption (255.6 g·d−1), MeHg EDI for most aquaculture products exceeded the USEPA reference dose (0.1 μg·kg−1·d−1), with THQ values up to 3.98, indicating significant health risks for high-end consumers. • • Only Penaeus monodon and Metapenaeus ensis were safe at all consumption levels, suggesting species-specific differences in Hg accumulation that can guide consumer choices and aquaculture species selection.
Abstract
Global aquaculture is expanding rapidly, with China leading in production and being the only country where aquaculture output exceeds wild catch. This growth raises concerns about environmental contamination, particularly mercury (Hg), and the safety of aquaculture products. This study investigated Hg accumulation and trophic transfer in a typical ecological mariculture area in Tangshan, Hebei Province, by measuring species-specific Hg concentrations in sediments and various aquatic organisms. Sediment total mercury (THg) levels were extremely low, averaging 4.0 ± 1.3 ng·g−1 dry weight (n=56), attributed to sandy/silty sediments with low adsorption capacity and minimal external/internal Hg inputs. In aquaculture fish, muscle THg and methylmercury (MeHg) concentrations were 59.7 ± 30.0 and 53.8 ± 29.2 ng·g−1 wet weight (n=7), respectively, comparable to wild fish from the same area. This is due to efficient trophic transfer and biomagnification of Hg, especially MeHg, along the food chain, influenced by food chain structure, primary consumer accumulation, and metabolic rates. At three seafood consumption levels (41.6–255.6 g·d−1), estimated daily intakes (EDI) of MeHg for Chinese adults ranged from 0.01 to 0.40 μg·kg−1·d−1, with target hazard quotients (THQ) from 0.13 to 3.98. Except for Penaeus monodon and Metapenaeus ensis, all other aquaculture products at high consumption levels exceeded the USEPA safety threshold for MeHg EDI and had THQ > 1, indicating potential health risks.
1. Introduction
Global aquaculture has become a dominant source of seafood, yet its environmental footprint, particularly regarding mercury (Hg) contamination, poses a significant challenge. Traditional mariculture often relies on external feed inputs and high-density stocking, which can introduce Hg into the system and enhance its bioavailability. In contrast, ecological mariculture models aim to mimic natural food webs and reduce external inputs, but their efficacy in mitigating Hg accumulation remains poorly understood. This study addresses this gap by examining a typical ecological mariculture area in Tangshan, China, focusing on Hg accumulation in sediments and biota, and the resulting health risks to consumers.
The central bottleneck in mariculture Hg management is the trade-off between productivity and safety. While ecological models may lower sediment Hg levels, they do not necessarily reduce Hg concentrations in cultured organisms due to efficient trophic transfer and biomagnification. This research provides critical empirical data on Hg speciation and distribution across trophic levels, enabling a quantitative health risk assessment. By linking sediment characteristics, food web dynamics, and human exposure, the study offers actionable insights for optimizing mariculture practices to minimize Hg risks while maintaining sustainable production.
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ZHANG Wei, YANG Zheng, LI Songjing, GAI Pengxue, CAO Fei, MENG Mei (2026). Accumulation, Trophic Transfer, and Health Risk Assessment of Mercury under Typical Ecological Mariculture Models. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025010803
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Frequently Asked Questions
What are the key factors controlling mercury accumulation in sediments under ecological mariculture, and how do they compare to traditional mariculture?
Sediment THg levels were extremely low (4.0 ± 1.3 ng/g dw), attributed to sandy/silty composition with low adsorption capacity and low external/internal Hg inputs. This contrasts with traditional mariculture, which often has higher sediment Hg due to feed additives and waste accumulation. The study suggests that ecological models can minimize sediment Hg contamination, but this does not necessarily translate to lower Hg in biota.
How does the trophic transfer efficiency of mercury in ecological mariculture compare to wild ecosystems, and what are the implications for human exposure?
Fish muscle THg and MeHg concentrations were comparable to wild fish, indicating efficient trophic transfer and biomagnification in ecological mariculture. This is likely due to the presence of longer food chains and higher metabolic rates in cultured species. The high MeHg levels in fish lead to potential health risks for consumers, especially at high consumption rates, as evidenced by THQ values exceeding 1 for most species.
Which aquaculture species are safest for human consumption in terms of mercury risk, and what consumption levels are recommended?
Penaeus monodon and Metapenaeus ensis were safe at all consumption levels, with MeHg EDI below the USEPA reference dose. For other species, high consumption (255.6 g/d) led to EDI exceeding the safe threshold. Therefore, consumers should limit intake of high-trophic-level fish and prefer shrimp species to minimize Hg exposure.
What are the methodological challenges in accurately assessing mercury speciation and trophic transfer in mariculture systems?
Challenges include distinguishing between natural and anthropogenic Hg sources, accounting for species-specific metabolic rates, and measuring MeHg in low-trophic-level organisms. The study used species-specific analysis and stable isotope techniques (if any) to trace trophic transfer, but further research is needed to refine models for predicting Hg accumulation under varying environmental conditions.
How can these findings inform policy and management strategies for sustainable mariculture?
The results highlight the need for monitoring Hg in aquaculture products and implementing consumption advisories, especially for high-trophic-level species. Management strategies should focus on optimizing feed composition to reduce Hg inputs and selecting species with lower bioaccumulation potential. Additionally, sediment management practices that enhance Hg sequestration could be explored, though the low sediment Hg suggests limited need in this specific ecological model.
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