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Explora: Environment
and Resource Trace elements in Mediterranean mussels

temporal pattern, with arsenic levels increasing from 2001
to 2002 before subsequently decreasing. Overall, the range
of arsenic concentrations measured in the tissues of M.
galloprovincialis varied from a minimum of approximately
8 µg/g to over 40 µg/g (dry weight). Oceanographic factors,
4
including salinity, nutrient concentrations, and water
circulation, were identified as significant contributors to
arsenic bioaccumulation.
The oceanographic characteristics of the northern
and central Adriatic are typically marked by elevated
variability in environmental conditions, largely due to
the combined and changing influence of the Po River
runoff, nutrient loads, atmospheric conditions, water
circulation, and stratification. The northern Adriatic is
generally more influenced by river inputs: surface waters
have reduced salinity (32 – 37%) and are supersaturated
with oxygen (O sat > 105%) for almost the entire year. Figure 2. Linear regression between arsenic (As) concentration (µg/g dry
2
On the contrary, different oceanographic conditions weight) in whole tissues of Mytilus galloprovincialis from the Adriatic Sea,
are observed in the central Adriatic, where higher sampled between 2001 and 2005, and salinity (Sal; psu). The correlation is
2
salinity waters (38.3 – 38.8%) and moderate oxygen statistically significant at a 99% of confidence interval (N=191, R =0.185;
undersaturation or supersaturation (O sat > 85%) Pearson=0.427, significance p<0.001), according to Fattorini et al. 4
2
are measured. Marine organisms typically contain
4
much higher concentrations of arsenic than freshwater gradient in the northern and central Adriatic Sea. This
species, suggesting that salinity influences arsenic gradient is associated with a notable gradient in arsenic
bioaccumulation. This hypothesis was first proposed for bioaccumulation in mussel populations, a natural and
marine fishes sampled from different sites of the North Sea unique characteristic of the Adriatic Sea, never observed
and Baltic waters, revealing a positive linear relationship before in other areas. 4
between arsenic concentrations and salinity. Laboratory 3.2. Natural and anthropogenic sources of mercury
33
experiments confirmed that higher salinity enhances the contamination in the Mediterranean
uptake of arsenobetaine (2-trimethylarsoniumylacetate,
C H AsO ) in several marine species, including the blue Mercury levels in the West Mediterranean are largely
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5
2
mussel (M. edulis), consistent with the proposed role of influenced by natural variations due to geological
arsenobetaine as an adventitiously acquired osmolyte for peculiarities. 34-37 Volcanoes in the Mediterranean, such
marine organisms. 31 as Etna, Stromboli, and Vulcano (Aeolian Islands, Italy),
are significant sources of mercury emissions. 35-37 Studies
To confirm the interaction between arsenic have shown that these volcanoes release mercury into the
bioaccumulation in mussels and salinity, a strong atmosphere, contributing to regional and global mercury
correlation was found between the data obtained by pollution and playing an important role in the overall
Fattorini et al., as summarized in the newly reedited mercury distribution in the Mediterranean. In addition,
4
36
Figure 2, which shows a linear regression between the two geothermal power plants and abandoned mining sites,
variables. As reported in the original study, this correlation particularly those associated with cinnabar (HgS) deposits,
was statistically significant at the 99% confidence level are additional sources of mercury emissions in the
2
(N=191, R =0.185; Pearson=0.427, significance p<0.001). Mediterranean. For instance, Mount Amiata in Tuscany
Figure 2 further highlights, using different colors, data (Italy) is a region with significant geothermal activity and
obtained from different monitoring years (from 2001 historical mining operations, largely responsible for the
to 2005), clearly demonstrating that salinity influences substantial release of mercury into the atmosphere and
arsenic bioaccumulation levels regardless of the sampling the water bodies. 37,38 Recent studies have challenged the
year, as the different data series largely overlap. notion that the Mediterranean is inherently more polluted
The distinctive conformation of the Adriatic Sea, with mercury than other oceanic regions and is known
a basin closed to the north and channeled toward the for its high levels of mercury in certain aquatic species,
southeast, is characterized by a constant and distinctive particularly top predator fishes and cetaceans, due to the
runoff from the Po River that determines a constant salinity ability of methylmercury – the most abundant chemical

Volume 2 Issue 2 (2025) 8 doi: 10.36922/eer.8078