Evaluation of the new role of the invasive species (Procambarus clarkii) as an environmental indicator in polluted watersheds

Abstract

Procambarus clarkii represents an invasive species of crayfish common in the rivers of the Iberian Peninsula, which replaced a previous invasive species of crayfish (Austropotamobius pallipes) and is now being replaced by a new invasive species (Pacifastacus leniusculus) in northern rivers. Leaving aside the ecological problems that these invasive species can cause, these organisms can be excellent candidates to act as environmental indicators in pollution processes that involves the interface water–sediment. In this work, the potential role of Procambarus clarkii as a bioindicator of pollution processes of mining origin is evaluated. Unlike previous research, which often focuses on snapshot assessments of contamination levels, our approach integrates historical data and continuous monitoring to provide a dynamic perspective on the impact of Hg and other metals on biotic and abiotic media over an extended period. A total of 330 crayfish were collected from 10 sites in Valdeazogues river, grouped by size, and analyzed for Hg, Pb, Cd, Cu, Zn, As, and Sb in abdominal muscle and hepatopancreas, with a complete characterization of sediment and water media. Crayfish data have shown that hepatopancreas and muscle present the highest average content of Zn (1,325 and 377 mg kg−1, respectively) and Cu (1,297 and 179 mg kg−1 respectively). Levels of Hg were higher in muscle (1.6 mg kg−1) than hepatopancreas (1.0 mg kg−1), with all muscle samples exceeding the EU maximum permissible level of 0.5 mg kg−1 for food. The sensitivity of P. clarkii has been sufficient to identify different sources of Hg, Pb and Zn contamination in the drainage system, and even agricultural sources of Cd downstream of the mining district. This versatile capability can be of application to large mining areas in the south of the Iberian Peninsula, especially throughout the Iberian Pyrite Belt.