Molina et al. 2023 — Mercury accumulation in Buenaventura Bay sediments
This study investigates the environmental variables controlling spatiotemporal dynamics of total mercury (tHg) accumulation in sediments of Buenaventura Bay, a tropical estuary on the Colombian Pacific coast heavily impacted by anthropogenic activity including illegal artisanal gold mining, domestic wastewater, and industrial discharges. Sediment samples were collected across four areas representing a salinity gradient from river-influenced interior to marine-influenced exterior, in both dry and rainy seasons, to depths of 15 cm. tHg in sediments was higher in the rainy season than the dry season and higher in interior estuarine areas than exterior areas, consistent with a pattern driven by organic matter transport and freshwater input from mercury-contaminated tributaries. Generalized additive modelling identified organic matter content and salinity as the primary predictors of tHg accumulation. Historical records show tHg concentrations in Buenaventura Bay water increased 22-fold between 1995 and 2002, attributed largely to artisanal gold mining in tributary rivers. The study documents a food-chain pathway by which mercury reaches benthic fauna and thence to fish harvested for human consumption.
Key numbers
tHg in sediments ranged from 0.2 to 0.6 µg/g dry weight in prior records (Velásquez and Cortés 1997), similar to values in other active mercury estuaries. Present study measured higher values in interior areas during rainy season. DMA-80 direct mercury analyzer detection limit 0.0001 µg/g; IAEA-405 CRM used for quality control with recovery at least 95%. tHg was higher in fine sediment fractions (less than 100 µm) and significantly higher in rainy versus dry season (PERMANOVA p less than 0.05). GAM explained tHg variation primarily from organic matter and salinity (AIC-selected model).
Methods (brief)
Sediment cores (50.8 mm diameter) to 15 cm depth, divided into three 5 cm layers; four areas, four seasonal sampling occasions in 2015. tHg by direct mercury analyzer (DMA-80 Milestone, Method 7473 EPA). Organic matter by calcination at 450°C. Particle size by sieve fractionation. Physicochemical water column variables measured in situ. Statistical analysis via PERMANOVA and Bayesian GAM. Limitations: sediment data only; no direct measurement of tHg in edible fish or shellfish from this study.
Implications
Certification: Provides supply-chain context for seafood originating from the Colombian Pacific coast. Buenaventura Bay is the most important port in Colombia; fish and shellfish harvested here face elevated tHg exposure through food-chain biomagnification pathways documented in this paper.
Courses: Useful for illustrating the artisanal gold mining-to-mercury-to-sediment-to-seafood pathway common across tropical Latin American coastal systems.
App: Not directly applicable to food concentration data; provides sediment-level tHg context for Colombian Pacific seafood origin framing.
Microbiome: Not addressed.