Comparative study on Hg bioaccumulation and biotransformation in Mediterranean and Atlantic sponge species

• Published in: Chemosphere (Oxford) Vol. 260; p. 127515
• Main Authors: Orani, Anna Maria, Vassileva, Emilia, Azemard, Sabine, Thomas, Olivier P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2020
• Subjects: Bio-monitoring; Marine sponges; Mercury; Mercury isotope ratios; Methyl mercury; Marine sponges; Mercury; Methyl mercury; Bio-monitoring; Mercury isotope ratios
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2020.127515

In this work we present an assessment of mercury (Hg) and methyl mercury (MeHg) bioaccumulation in different species of marine sponges collected off the Northwestern Mediterranean and Northeastern Atlantic coasts. Overall the results showed significant accumulation of Hg in sponges, with the Mediterranean sponge Chondrilla nucula exhibiting the highest total Hg content (up to 0.5 mg kg−1) and bio-concentration factor (BCF) up to 23. A significant inter-species variability of Hg bioaccumulation was observed among species collected at the same site. The sponges, collected in marine environment contaminated with Hg show consistently higher Hg accumulation, meaning that the bioaccumulation is proportional to the Hg availability in the surrounding environment. Different extraction protocols were tested for MeHg analysis and, generally, a low MeHg ratio in Hg species (4% and 17% average for Mediterranean and Irish sponges respectively) was detected suggesting a possible demethylation process and therefore a promising role of sponges for Hg bioremediation Additionally, the Hg isotopic composition in these organisms was determined and it showed that MDF (mass dependent fractionation) is the main process in sponges, with the absence of significant MIF. This result suggests a dominant role of associated microbial population in the methylation and/or demethylation processes.
•Hg accumulation and biotransformation was studied in 6 sponge species.•An extraction procedure for MeHg determination was developed and optimized.•Hg and MeHg results show that sponges are appropriate organisms for bio-remediation.•Hg isotopic composition was determined in marine sponges for the first time.•Sponge microbial symbionts are likely responsible for Hg biotransformation.