Bioaccumulation of dietary CrPic, Cr(III) and Cr(VI) in juvenile coral trout (Plectropomus leopardus)

The form of chromium (Cr) is an important factor that influences its bioavailability and potential toxicity, while the difference of Cr bioaccumulation between organic and inorganic Cr has been rarely investigated. The present study compared the bioaccumulation of organic Cr (e.g., chromium picolinate (CrPic)) and inorganic Cr (e.g., trivalent (Cr(III)) and hexavalent (Cr(VI))) in juvenile coral trout (Plectropomus leopardus). The fish were exposed to a gradient level of different forms of dietary Cr for 66 days. Then the Cr bioaccumulation in fish were comparatively quantified between CrPic, Cr(VI) and Cr(III) groups. The results showed that the Cr bioaccumulation was form- and tissue-specific, dose- and time-dependent. Specifically, the newly bioaccumulated Cr in fish generally increased with the increasing dietary Cr level and exposure time, while the CrPic groups accumulated the highest Cr in most cases, followed by Cr(VI) and Cr(III) groups. The highest Cr content was observed in gut for CrPic groups, while it was highest in heart for Cr(VI) and Cr(III) groups, followed by kidney, skin, fin, liver, gill, bone, eyes and muscle in order. Overall, the results here firstly demonstrated that the dietary organic Cr(III) had significantly higher bioaccumulation than inorganic Cr (Cr(III) and Cr(VI)). Our findings suggested the complexity and variability of form-specific Cr bioavailability and toxicity should be cautiously evaluated in aquatic environments, which has been largely overlooked previously.