The abundance and speciation of mercury in the Adriatic plankton, bivalves and fish – a review

Abstract

This article presents an overview of available research on mercury speciation in the most studied biota of the Adriatic Sea as a specific biogeochemical subunit of the Mediterranean. We present current knowledge about mercury concentration, speciation, spatial distribution and temporal changes in plankton, bivalves and fish from the Adriatic Sea. Results from mercury speciation studies in marine organisms are used to describe the extent of mercury bioaccumulation in the Adriatic Sea. Mercury biogeochemical cycle in the Adriatic is characterised by increased mercury concentrations from the water column, through plankton, bivalves and smaller fish to predator fish species. Although the Adriatic Sea has the highest mercury concentration in the whole Mediterranean Sea, fish species at the higher trophic levels have similar mercury concentrations everywhere in the Mediterranean, indicating incomplete understanding of the transfer mechanisms of mercury from seawater to upper trophic levels. As consumption of (contaminated) food is the main route of human exposure to mercury, it is of great importance to understand the influence of mercury contamination in the Adriatic Sea.

Mercury concentrations in biota in the Mediterranean Sea, a compilation of 40 years of surveys

“…Benthic organisms from neritic habitats are the most highly represented group. As expected, there are a large number of Mediterranean mussel ( Mytilus galloprovincialis ) samples, which are frequently used as a favoured bioindicator 27,33,34 .…”

“…Differences in fish habitat, fish age/size, and the possibility of variable environmental mercury loadings make an exact assessment difficult without detailed modelling. A recent review of mercury speciation in the Adriatic biota showed no significant differences in fish mercury with time 27 . Possible sample contamination and the use of mercury-contaminated acids for sample digestion might have caused errors in older studies since results were often not corrected for blanks (this information is not commonly reported in older studies).…”

“…zooplankton). Mercury concentrations have been decreasing in the Adriatic zooplankton with time 27 . However, the use of different sampling methods, sample preparation procedures, and analytical methods does not allow for an assessment of contributing factors in this small dataset.…”

“…In a few cases, records report Hg(II) (4) and organic mercury HgO (434), which probably refers to MeHg even if the analytical procedure is not available to see exactly what was determined. Data are limited to only a few marine eco-regions and are mostly concentrated in the northern part of the Mediterranean, where polluted areas prevail 27,32 . Data are limited in the southeastern part of the Mediterranean Sea for two reasons: (1) fewer research/monitoring efforts in Countries facing the Sea, and (2) possible publication of datasets in national languages that are not known by the Authors.…”