Heavy metals, OCPs, PAHs, and PCDD/Fs contamination in surface sediments of a coastal lagoon (Valli di Comacchio, NW Adriatic, Italy): Long term trend (2002-2013) and effect on benthic community.

Surface sediments contamination (heavy metals, organochlorine pesticides, polycyclic aromatic hydrocarbons, polychlorinated dibenzodioxins and dibenzofurans) and benthic community of the Valli di Comacchio, were analysed from 2002 to 2013. Along the studied period, most of analysed pollutants did not exceed thresholds for Good chemical status of sediments. In 2008, a peak of contamination was observed, with total PAHs and OCPs exceeding their threshold. Considering metals, Ni and Cr exceeded their thresholds, but not the background levels for the area, suggesting natural enrichment; conversely Pb exceeded background levels for the area in many samples, but it exceeded its sediment quality thresholds only in few samples (2006, 2009, 2011). Conversely, the ecological status evaluated though AMBI and M-AMBI, was below the Good/Moderated thresholds established by WFD in most of the studied years. In the 11 yrs-study period, the benthic community showed a very weak response to chemical contamination.

Organic aggregates formed by benthopleustophyte brown alga Acinetospora crinita (Acinetosporaceae, Ectocarpales).

This work presents the elemental, polysaccharide, and fatty acid compositions of benthic aggregates formed by the filamentous brown alga Acinetospora crinita, which are widely spread on the rocky bottoms of the Mediterranean Sea. The aggregates can be characterized as mineralized centers in which regeneration of nutrients and recycling of dissolved organic matter actively occur and favor the development of an abundant phytoplankton community. Analyses of the stable isotopes of C and N display their marine origin and could provide evidence of the processes that occur inside/outside of the aggregates. The monosaccharide compositions of Adriatic and Tyrrhenian mucilages produced by brown alga A. crinita were quite similar. In particular, the Adriatic sample compositions resembled the average composition of the Tyrrhenian high molecular weight exopolymers, and the observed differences could be ascribed to different degradation stages. The fatty acid patterns found for the aggregates were similar to those observed in the isolated A. crinita algae with variable contributions from embedded diatom species. The bacterial contribution to the fatty acid pool was quite low, most likely due to the known poor conditions for their heterotrophic growth.