RESEARCH ARTICLE Restoration impact of an uncontrolled phosphogypsum dump site on the seasonal distribution of abiotic variables, phytoplankton and zooplankton along the near shore of the south-western Mediterranean coast Amira Rekik & Sami Maalej & Habib Ayadi & Lotfi Aleya Received: 5 September 2012 / Accepted: 29 October 2012 / Published online: 13 November 2012 # Springer-Verlag Berlin Heidelberg 2012 Abstract 'In connection with the Taparura Project, we stud- ied the distribution of phytoplankton and zooplankton com- munities in relation to environmental variables at 18 stations sampled during four coastal cruises conducted between October 2009 and July 2010 on the north coast of Sfax (Tunisia, western Mediterranean Sea). The inshore location was largely dominated by diatoms (66 %) represented essen- tially by members of the genera Navicula, Grammatophora, and Licmophora. Dinophyceae were numerically the second largest group and showed an enhanced species richness. Cyanobacteriae developed in association with an important proliferation of colonial Trichodesmium erythraeum, contrib- uting 39.4 % of total phytoplankton abundances. The results suggest that phytoplankters are generally adapted to specific environmental conditions. Copepods were the most abundant zooplankton group (82 %) of total zooplankton. A total of 21 copepod species were identified in all stations, with an over- whelming abundance of Oithona similis in autumn and sum- mer, Euterpina acutifrons in winter, and Oncaea conifera in spring. The phosphogypsum restoration had been acutely necessary allowing dominant zooplankton species to exploit a wide range of food resources including phytoplankton and thus improving water quality. Keywords Phytoplankton . Zooplankton . Environmental parameters . Phosphogypsum . North coast of Sfax Introduction The Taparura Project is part of an environmental policy and management program aimed at tackling the pollution threat- ening the beaches and coastal waters of Sfax (Hamza- Chaffai et al. 1997; Ben Brahim et al. 2010; Abdennadher et al. 2012). The first step of the project consisted of clean- ing a zone of 400 ha, removing 4.3 millionm 3 of polluted soil including 1.7 million m 3 of phosphogypsum. The latter, stockpiled along the coastline 6 m above sea level, untreat- ed, in an uncontrolled landfill of more than 150 ha, is an industrial by-product of the phosphoric acid produced by the wet process from natural phosphate rock (Tayibi et al. 2009). Phosphogypsum is mainly composed of gypsum but also contains high levels of impurities such as phos- phates, fluorides, sulfates, naturally occurring radionuclides, heavy metals, and other trace elements, and its management is among the most serious problems currently facing the phosphate industry (Louati et al. 2001; Tayibi et al. 2009). Furthermore, recent studies have shown that, in these waters, prior to restoration, as expected, large amounts of allochthonous phosphorus and organic matter developed, affecting the structure and functioning of the plankton com- munities under study, namely phytoplankton, ciliates, and crustacean zooplankton (Rekik et al. 2012). It is therefore of interest to explore whether species perform better or worse under the specific conditions of phosphogypsum restoration and how this translates into terms of species richness. Indeed, ecological knowledge of phosphogypsum impact on plankton communities in aquatic ecosystems is scant. We recently reported what is, as far as we know, the only published study in which, contrary to our Responsible editor: Philippe Garrigues A. Rekik : S. Maalej : H. Ayadi Département des Sciences de la Vie. Unité de recherche LR/UR/ 05ES05 Biodiversité et Ecosystèmes Aquatiques, Faculté des Sciences de Sfax, Université de Sfax, Route Soukra Km 3.5–BP 1171, CP 3000 Sfax, Tunisia L. Aleya (*) Laboratoire de Chrono-Environnement, Université de Franche-Comté, UMR CNRS 6249, Place Leclerc, 25030 Besançon Cedex, France e-mail: lotfi.aleya@univ-fcomte.fr Environ Sci Pollut Res (2013) 20:3718–3734 DOI 10.1007/s11356-012-1297-y