Metal(loid)s in suspended particulate matter and plankton from coastal waters (Gulf of Trieste, northern Adriatic Sea)

PurposeThe levels of metal(loid)s at the beginning of the coastal pelagic food web, providing an insight into accumulation in the suspended particulate matter (SPM) and size-fractionated plankton, were studied in the shallow coastal marine environment of the Gulf of Trieste (northern Adriatic Sea) affected by the metal polluted Isonzo/Soca River as a result of historical Hg, and Pb and Zn mining activities in the hinterland.Materials and methodsLevels of metal(loid)s were investigated in suspended particulate matter (0.45-20 mu m) and fractionated plankton (20-50 mu m, 50-200 mu m, > 200 mu m) collected monthly at the Marine Biology Station oceanographic buoy Vida in the southern part of the Gulf of Trieste.Results and discussionConcentrations of meta(loid)s showed the following order Al,Fe > Zn,Mn > Ni > Cu,Cr > As,Pb,V > Co > Se > Cd > U > Hg and were similar to those of dissolved metal(loid)s of the gulf waters (Al,Fe > Zn > Cu > V > Mn > As > Ni,Se > U,Cr > Cd > Hg) where Hg, Cu, Cr and Se were significantly associated with colloidal organic matter (< 0.2 mu m, > 5 kDa). The partition of metal(loid)s between their particulate phase and free ion and inorganic complexes in the water (K-pd) confirmed a strong binding of Hg, Al, Mn, Fe, Cr and Pb onto seawater particles. In general, the metal(loid) data for SPM and plankton showed high levels in the 50-200 mu m microplankton fraction. Larger plankton fractions, especially > 200 mu m, contain a lower amount of metal(loid)s associated with mineral particles originating from sedimentary pelite resuspension and riverine inflows. Variations of metal(loid)s levels in SPM and plankton fractions were related to their biomass (ash free dry weight-AFDW) and organic matter, and mineral (inorganic) content, which is difficult to separate from biogenic particles including organisms, and to the taxonomic composition and feeding behaviour of organisms in various fractions.ConclusionsThe Redfield's stoichiometric concept including metal(loid)s in the coastal marine plankton (SPM and mesozooplankton) appears unreliable. The bioconcentration factors (log BCFs) of the studied metal(loid)s, ranging between 4 and 6 for Hg, Fe, Mn, Cr, Pb, Co, Zn, Ni, As, Cu and V and lower for Se and U both in micro- and mesoplankton, can possibly be used in micro- and especially in mesoplankton fraction less impacted by mineral metal(loid)s. This should be considered when establishing the metal(loid)s levels at the base of the coastal and estuarine food webs, at the onset of marine bioaccumulation, to provide information for marine organisms consumed by humans.

Automated summary

This study examined the levels of metal(loid)s at the beginning of the coastal pelagic food web and their accumulation in suspended particulate matter and size-fractionated plankton in the Gulf of Trieste.