First evidence of trace elements bioaccumulation in the Mediterranean coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

The concurrent action of climate change and the accumulation of anthropogenic pollutants represent a major threat to coastal marine environments. In this context, the effects on marine calcifiers are particularly relevant as they sustain marine biodiversity. Corals, as long-living benthic organisms, are capable of bioaccumulating heavy metals in response to environmental factors and anthropogenic impacts. Their skeletons incorporate these metals by absorbing those dissolved in seawater, which are then retained indefinitely as they become encapsulated within the overlying carbonate formed during new skeletal growth. This characteristic makes corals valuable sentinels for monitoring environmental contamination and its potential ecological consequences. This study aims to assess the levels of trace element accumulation in Mediterranean scleractinian corals, using the zooxanthellate solitary coral Balanophyllia europaea as a reporter species. Populations from impacted and pristine sites were sampled. Here, we focus on coral specimens collected in Calafuria (43°27′ N, 10°21′ E, Italy, Ligurian Sea), a bay located southeast of Livorno harbor, which is one of the largest seaports in the Mediterranean Sea. Coral samples were separated into three biological compartments: host tissue, symbiotic algae, and skeleton. Trace element concentrations (Al, As, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Se, Sn, Zn) were quantified using inductively coupled plasma (ICP-OES). Preliminary results provide insight into the differential accumulation patterns of heavy metals across coral compartments and highlight the potential of B. europaea as a bioindicator of heavy metal pollution in the Mediterranean Sea.