Author: uset

RECENT ADVANCES IN THE BIOMONITORING OF TRACE ELEMENTS USING POSIDONIA OCEANICA (L.) DELILE
J. Richir* and S. Gobert (* jonathan.richir@ulg.ac.be)
Laboratory of Oceanology, University of Liège ULg, Liège, Belgium

Introduction
● As, V, Ag, Be, Al, Mn, Co, Se, Mo, Sn, Sb and Bi, categorized as trace elements (TEs) of “environmental emerging concern”, have been subject to nearly no biomonitoring survey with Posidonia oceanica, contrary to Cr, Ni, Cu, Zn, Cd, Pb and Fe.
● Little is known about TE kinetics within P. oceanica meadows.

Fig.1. Above left map - 18 sites along Provence-Alpes-Côte d’Azur (PACA; 1-11) and Corsican (I-VII) coasts (France) sampled in April 2007 for P. oceanica. Observed contaminations of sites by TEs are detailed. Above right map - 9 sites (A1-A9) along a radial at the back of the Ajaccio Bay sampled in May 2010 for P. oceanica. Below graphs - variations of Bi levels (µg.gDW-1) in P. oceanica sampled at small (Ajaccio Bay) or large (French Mediterranean littoral) spatial scales.

Material and methods
● TE levels were biomonitored in P. oceanica sampled at the scale of the French Mediterranean littoral and along a radial at the back of the Ajaccio Bay (Corsica, France; Fig.1).
● TE bioaccumulation was seasonally studied for 3 years in P. oceanica shoots sampled in the pristine Calvi Bay.
● TE kinetics were experimentally studied in P. ocenica exposed to realistic environmental levels of a multielement solution.
● TE analyses were performed by DRC-ICP-MS.

Conclusion
As TE concentrations and kinetics evolve seasonally and spatially in P. oceanica according to the synergistic effect between environmental bioavailable TE levels and the plant ecophysiology, consensuel monitoring protocols should be developped to improve its use as bioindicator of TE pollution.

Results and discussion
● P. oceanica efficiently bioaccumulated TEs of environmental emerging concern (Fig.1). High levels could be linked to specific anthropic activities: mining (Sb), agriculture (Mo), storage and refinement of oil products (V), presence of major urban centres (Bi) etc.
● P. oceanica TE levels could vary as much at small and at large spatial scales (e.g. Bi in Fig.1). Representative sampling sites should therefore be elected with care when planning a monitoring survey.
● P. oceanica responded rapidly and proportionally when exposed to realistic environmental contamination levels (e.g. Cu in Fig.2). Accumulated amounts of TEs could then be eliminated when pristine conditions were restored, or redistributed between plant compartments.
● P. oceanica TE levels varied seasonally according to the plant biological cycle (e.g. Bi and the ratio between surfaces of adult and intermediate leaves in Fig.3).

Fig.2. Cu (µg.gDW-1) uptake and loss kinetics in P. oceanica leaves and rhizomes, experimentally in situ contaminated in June 2009. The contamination period lasted 5 days (C0-C5), the decontamination period 15 days (D0-D15). Seawater (SW) bioavailable Cu (µg.L-1) was measured in the experimental setup and in the reference seagrass meadow throughout the use of diffusive gradients in thin films (DGTs) devices.

Fig.3. Seasonnal evolution of Bi concentrations (µg.gDW-1) in P. oceanica leaves sampled between years 2008-2010 in the pristine Calvi Bay, and of the ratio between foliar surfaces of adult and intermediate leaves (SAL/SIL).