Management priorities for marine invasive species.

Managing invasive alien species is particularly challenging in the ocean mainly because marine ecosystems are highly connected across broad spatial scales. Eradication of marine invasive species has only been achieved when species were detected early, and management responded rapidly. Generalized approaches, transferable across marine regions, for prioritizing actions to control invasive populations are currently lacking. Here, expert knowledge was elicited to prioritize 11 management actions for controlling 12 model species, distinguished by differences in dispersion capacity, distribution in the area to be managed, and taxonomic identity. Each action was assessed using five criteria (effectiveness, feasibility, acceptability, impacts on native communities, and cost), which were combined in an 'applicability' metric. Raising public awareness and encouraging the commercial use of invasive species were highly prioritized, whereas biological control actions were considered the least applicable. Our findings can guide rapid decision-making on prioritizing management options for the control of invasive species especially at early stages of invasion, when reducing managers' response time is critical.

Variation along the year of trace metal levels in the compartments of the seagrass Posidonia oceanica in Port El Kantaoui, Tunisia.

The accumulation of the five trace metals (TMs) cadmium, copper, lead, nickel and zinc was measured in Posidonia oceanica leaves. Shoots were seasonally sampled at 8-10-m depth from four stations located in Port El Kantaoui area, Tunisia, during four campaigns performed in 2012. Levels of the five TMs were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES) in three compartments of P. oceanica shoots: blades and sheaths of adult leaves and intermediate leaves. Results showed a preferential accumulation of Cd, Pb, Ni and Zn in adult leaf blades. Therefore, we focus on the study of this compartment. TM levels of blades of adult leaves decreased in the following order: Zn > Ni > Cu > Pb > Cd, irrespective of the season. Levels of the five TMs significantly differed between seasons (p < 0.01). Levels of Cd and Cu showed a seasonal pattern: Cd decreased from spring to winter while Cu increased during that same period of time. A significant correlation (p < 0.01) was found between Cd-Cu and Cd-Pb. A significant correlation (p < 0.05) was also noted between Cd-Ni in the adult leaf blades. A relationship was recorded between the foliar surface of the adult leaf blades and Zn accumulation. This survey allowed to highlight the annual variation of TM accumulation in adult leaf blades of P. oceanica, in relation with ecophysiology of this seagrass. Therefore, this study reinforces the usefulness and the relevance of this compartment of P. oceanica, easy to sample without destruction of whole shoot, as a bioindicator of Zn, Ni, Cd and Pb contamination.