WHICH CONTAMINATION OF THE SEAGRASS POSIDONIA OCEANICA ALONG THE PROVENCE COAST (FRANCE, NW MEDITERRANEAN SEA)? Mélanie OURGAUD 1, HARMELIN-VIVIEN M. 1, RUITTON S. 1, 1 2 2 3 BOUDOURESQUE C.F. , BUSTAMANTE P. , CHURLAUD C. , WAFO E. 5th Mediterranean Symposium on Marine vegetation | 27-28 October 2014 | Portoroz, Slovenia |
(1) Mediterranean Institute of Oceanography (MIO), CNRS/INSU/IRD UM 110, Aix-Marseille Université, France - (2) LIttoral ENvironnement et Sociétés (LIENSs), Université de La Rochelle - (3) Faculté de Pharmacie de Marseille, Laboratoire de Chimie Analytique, Qualitologie et Nutrition, Aix-Marseille Université Mélanie Ourgaud represented by Sandrine Ruitton (PhD)
[email protected] PhD student – MIO - Marseille
Abstract Contamination by organic (PCBs) and inorganic (As, Ba, Cd, Cr, Cu, Hg, Ni, Pb and Zn) contaminants in Posidonia oceanica was studied in adult leaves and rhizomes for 4 sites exhibiting different levels of human pressure near the city of Marseilles (3 sites), and Hyères (the reference site)
Higher values were recorded at Marseilles, due to the vicinity of major urban, harbour and industrial centres, but only for trace elements. More contaminants were accumulated in adult leaves than in rhizomes. The leaves could be used as a tracer of spatial contamination (TEs) and as a tool for water quality evaluation to assess the contamination level in food webs
Background context As part of a study of food webs and contaminant bioaccumulation in Posidonia oceanica meadows, contaminant levels in this plant was studied to test their relation to human pressure by comparing different sites with a contrasting degree of inputs and by analysing different parts of the seagrass
intensive human activities on coastal marine habitats matter of concern for polychlorinated biphenyls (PCBs) and Trace Elements (TEs) in environment
endemic Posidonia oceanica used as a contaminant bioindicator to evaluate the bioavailable levels of contaminants for living organisms in seagrass meadows © Ourgaud. M
Results The concentration of most contaminants varied considerably in leaves, depending on location (Tab. 1). TE concentrations decreased following the order: Zn > Ni > Cu > Cd, Pb, Ba, As, Cr > Hg, from 192.1 for Zn to 0.1 µg g-1 dry mass for Hg, which was in agreement with previous studies (Lafabrie et al. 2008). Values of As, Ba, Cr and Hg in leaves were lower at Hyères than at the Marseilles sites. However, no significant spatial difference was observed for PCBs (mean 14.4 ± 1.8 µg kg-1 dry mass)
Tab.1| Mean concentrations of PCBs (µg kg-1 dry mass ± SD) and TEs (µg g-1 dry mass ± SD) measured in P. oceanica leaves from PC (Plateau des Chèvres), PB (Prado Bay), CB (Côte Bleue) and HY (Hyères) from the highest to the lowest human pressure. ns = non significant
Discussion & ‘ Take Home ’ LEAVES CONTAMINATED FIRST | trace elements |
RHIZOMES CONTAMINATED FIRST | PCBs |
RHIZOMES NOT DISCRIMINENT
Higher concentrations of As, Ba, Cd, Cr, Pb, and Zn were detected in leaves than rhizomes reflect their preferential uptake from the water by photosynthetic tissues
PCBs and Hg were more heavily accumulated in rhizomes than leaves. Higher Hg levels can be explained by the existence of bacteria in the rhizosphere (De Sousa et al., 1999)
No difference was observed in rhizomes between study sites (results not shown)
Methodology Shoots of P. oceanica were collected in winter 2012 at 3 sites near Marseilles (Plateau des Chèvres: PC, Prado Bay: PB, Côte Bleue: CB; from the highest to the lowest impacted), and in the Gulf of Hyères (HY), a reference site in a less urbanized area
PCBs (sum of 32 individual congeners) were analysed by gas chromatography with an Agilent Technologies HP 6890 equipped with a 63Ni electron capture detector
Total Hg was analysed using an Advanced Mercury Analyser. As, Ba, Cd, Cr, Cu, Ni, Pb and Zn analyses were carried out with Varian Vista-Pro ICPOES and a Thermo Fisher Scientific X Series 2 ICP-MS
Conclusion Posidonia oceanica is located at the base of the food web in shallow Mediterranean ecosystems and is probably a main source of contaminants for primary consumers. Therefore, the assessment of contaminants in P. oceanica leaves may provide useful indications on the spatial contamination and the potential transfer of these elements to higher consumers in food webs
References DE SOUZA M., HUANG C., CHEE N., TERRY N. (1999) - Rhizosphere bacteria enhance the accumulation of selenium and mercury in wetland plants. Planta 209 (2):259-263 LAFABRIE C., PERGENT-MARTINI C., PERGENT G. (2008) - Metal contamination of Posidonia oceanica meadows along the Corsican coastline (Mediterranean). Environ. Pollut. 151 (1): 262-268
Acknowledgements This study was funded by grants from the ‘Région Provence Alpes Côte d’Azur’, the ‘Agence de l’Eau Rhône Méditerranée-Corse’, the City of Marseille and the ‘OHM littoral méditerranéen | LABEX DRIIHM. Thanks are also expressed to : (1) fishermen Jean Canale and Daniel Péronnet, (2) our colleagues and friends of OSU Pytheas, (3) MIO and (4) GIS Posidonie for their valuable help during field sampling LABEX DRIIHM
