Investigation of metals in organisms from different trophic levels of the southwest Caspian

The Caspian Sea, as the largest land-enclosed drainage area in the world has been endangered by various environmental pollutants, discharged from coastal catchment. In this study the trophodynamics of metals are investigated in different organisms from the Caspian food web. Furthermore, the species with potential bio-indicator abilities have also been distinguished. Nine species including three invertebrates Mnemiposis leidyi, Cerastoderma glucaum and Balanus improvises; five fish species Neogobius spp, Atherina boyeri, Alburnus chalcoides, Rutilus kutum and the Caspian seal Phoca caspica were studied in three regions of the southwestern Caspian: i.e. Astara, Anzali and Chaboksar. The stable isotope of primary producer (POM) was very various in each region compare to those from primary consumers. Phoca caspica had the highest average δ15N and TLs as the top of the food chain. The concentrations of metals for the most samples of fish were below the detection limits; while the concentrations were detected in most invertebrate samples. Our results suggested the abilities of Cerastoderma glucaum as indicator of Ni and Co contamination. Balanus improvises had a high capacity for Zn, Sr, Mn and Cu bioconcentration. By comparing ln-concentration of metals vs. TLs, no metal biomagnification was observed. The marine pollution index in Anzali region was higher than those in Astara and Chaboksar regions. While this study provides the basic data from southwestern Caspian Sea; C. glucaum and B. improvises could be proper bioindicator species for worldwide comparison of metal pollution.