Bioaccumulation of Mercury in Marine Algae from Dakar Coast (Senegal) and Galician Rias (Spain)

Abstract

Algae samples from Dakar coast (Senegal) and Galician Rias (Spain) were analyzed by cold vapor atomic absorption spectrometry (CV-AAS) to assess the bioaccumulation of mercury in the two aquatic systems. In this work, the contents of inorganic mercury and total mercury were determined. Simplified analytical procedures (microwave digestion and ultrasonic assisted extraction) were used for sample preparation. A reference material (BCR-60) was used to validate the analytical procedures used for sample preparation. The results of the analysis show that the total mercury contents found in algae samples from the Galician Rias are relatively similar to those found in algae samples from the Dakar coast. However, the inorganic mercury content of the algae from Pontevedra Ria was considerably higher than that found in the algae samples from Vigo Ria. The distribution was observed for inorganic mercury and total mercury, indicating that inorganic mercury is the major mercury species that bioaccumulates in marine algae. The inorganic mercury contents were always approximately equal to those of total mercury in the algae samples and a satisfactory correlation (p <0.0001; r = 0.9997) was obtained between them. Finally, the ANOVA analysis indicates that no significant difference (F = 0.165; p = 0.809) was found between the algae of the two aquatic systems (Dakar coast and Galician Rias).

Transformation of Mercuric Ions to Mercury Nanoparticles in Diatom Chaetoceros curvisetus

“…A recent study clarified that particulate Hg (<0.5 μm) accounts for 20–50% of total Hg in sediments, but nanoscale Hg particles have not been explored. Diatoms can bioaccumulate Hg from seawater, and now, we found that it can constantly form HgNPs inside diatom cells. According to the dose–effect among intracellular Hg­(II) concentrations and HgNP production found in this study, the concentrations of HgNPs by the diatom in the environment were extremely underestimated than those under laboratory conditions.…”

“…To investigate the sizes and distribution of particulate HgS, diatom Chaetoceros curvisetus was subjected to acute exposure to 0.5–100.0 μg L –1 Hg­(II) at one time and without changing the medium during exposure. This ensured intracellular Hg­(II) concentrations were environmentally relevant concentrations, owing to the bioaccumulation of cells in a realistic environment. ,, Chaetoceros curvisetus in the midexponential growth phase was harvested by centrifugation (2000 g , 25 °C, 10 min), then rinsed with 5 mL of PBS (10 mmol L –1 ) three times, and finally resuspended in the exposure medium with the addition of HgCl 2 . To investigate Hg accumulation and transformation with time extension, Chaetoceros curvisetus was exposed to 10.0 μg L –1 Hg­(II) for 0, 1, 2, 3, and 4 days.…”

“…This ensured intracellular Hg(II) concentrations were environmentally relevant concentrations, owing to the bioaccumulation of cells in a realistic environment. 17,18,38 Chaetoceros curvisetus in the midexponential growth phase was harvested by centrifugation (2000g, 25 °C, 10 min), then rinsed with 5 mL of PBS (10 mmol L −1 ) three times, and finally resuspended in the exposure medium with the addition of HgCl 1, 2, 3, and 4 days. Similarly, to investigate Hg accumulation and transformation with concentration changes, Chaetoceros curvisetus was exposed to 0.5, 1.0, 5.0, 10.0, and 100.0 μg L −1 Hg(II) for 4 days.…”

“…This regulatory effect can be attributed to bioaccumulation and transformation of Hg by algae, which further influence the fate and transport flux of Hg in the ocean . The concentration factors (VCFs) of inorganic Hg in algae are 0.5–5 × 10 4 with intracellular Hg concentration at the range of 9.7–602.8 nmol g –1 (dry weight). , These make it difficult to calculate Hg transport flux via models due to the underestimated biological transformation of Hg . For better understanding of the marine Hg cycle and accurately assessing marine Hg flux, it is of vital importance to study the transformation of different Hg forms mediated by algae, particularly the formation of HgNPs in algae.…”

“…16 The concentration factors (VCFs) of inorganic Hg in algae are 0.5−5 × 10 4 with intracellular Hg concentration at the range of 9.7−602.8 nmol g −1 (dry weight). 17,18 These make it difficult to calculate Hg transport flux via models due to the underestimated biological transformation of Hg. 19 of vital importance to study the transformation of different Hg forms mediated by algae, particularly the formation of HgNPs in algae.…”