In this paper we explored the heavy metal bioaccumulation (Cd, Cu, Pb and Zn) in Procambarus clarkii, a crayfish
recently suggested as a potential bioindicator for metals pollution in freshwater systems. The present study is focused
on crayfishes populations caught in a heavily polluted industrial and in a reference sites (Central Italy),
though the results are generalized with a thorough analysis of literature metadata. In agreement with the literature,
the hepatopancreas (Hep, detoxification tissues) of the red swamp crayfish showed a higher concentration
of heavy metals in comparison to the abdominal muscle (AbM, not detoxification tissues) in the sites under scrutiny.
Hep/AbM concentration ratio was dependent on the specific metal investigated and on its sediment contamination
level. Specifically we found that Hep/AbM ratio decreases as follows: Cd (11.7) N Cu (5.5) N Pb (3.6) N Zn
(1.0) and Pb (4.34) N Cd (3.66) N Zn (1.69) N Cu (0.87) for the industrial and reference sites, respectively. The
analysis of our bioaccumulation data as well as of literature metadata allowed to elaborate a specific contamination
index (Toxic Contamination Index, TCI), dependent only on the bioaccumulation data of hepatopancreas and
abdominal muscle. In the industrial site, TCI expressed values much higher than the unit for Cd and Cu,
confirming that these metals were the main contaminants; in contrast for lower levels of heavy metals, as
those observed in the reference site for Cu, Zn and Pb, the index provided values below unit. TCI is proposed as
a useful and easy tool to assess the toxicity level of contaminated sites by heavy metals in the environmental
management.
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