Colloidal Metal(loid)s and their Bioaccumulation in Plankton in a Coastal Ecosystem
Abstract
The Gulf of Trieste (northern Adriatic Sea) is principally affected by the metal polluted Isonzo/Soča River, the main tributary to the gulf, as a result of historical Hg, and Pb and Zn mining and smelting activities in Idrija (W Slovenia) and Raibl (NE Italy), respectively. Colloidal organic matter (COM) in the gulf (>5 kDa), represents about ¼ of dissolved organic carbon (DOC) and, according to 1H NMR, is composed of polysaccharides, lipids, proteins and carboxyl-rich alicyclic molecules (CRAM) and humics. COM from the Isonzo/Soča River differed from the marine COM containing higher protein/CRAM and humic levels. An analysis of metal(loid)s of the gulf waters, made using ICP-MS and CVAFS (Hg), showed that Hg (nearly 100%), Cu (20%), Cr (10%) and Se (10%) have the highest affinity to COM. Similarly, to COM, the levels of colloidal Hg and Cu peaks in summer, due to their sequestration in accumulated COM, but later decreased. Me/Corg. ratios (Co, Cd, Hg < U, Cr, Ni, Mn < As, Zn, Cu, V < Fe) can be explained by composition of COM and variable background concentrations of studied metal(loid)s in the northern Adriatic. The salinity gradient in the Isonzo/Soča River mouth showed flocculation of Al and Cu and desorption of V, Mn, As, Se, Cd, U and Hg from the riverine particles with increasing ionic strength while Fe, Cr, Ni, Zn and Pb did not correlate with salinity. Analyses of metal(loid)s in SPM (0.45-20 µm) and fractionated plankton (20-50, 50-200, >200 µm) showed increasing concentrations of Cr, As, Se, U and Pb with size while the highest levels of Fe, Mn, Cu, Zn (essential metals), Ni, V and Hg occur in the 50-200 µm fraction, and Co and Cd in the 20-50 µm fraction. This can be related to the taxonomic composition and feeding behavior of organisms in various fractions: mostly diatoms, dinoflagellates and nanoflagellates in the 20-50 µm fraction, microzooplankton with ciliates in the 50-200 µm fraction and mesozooplankton with copepods, cladocerans and dinoflagellates in the >200 μm fraction. BCFs were similarly distributed, considering that Hg and to a lesser extent Cu, Cr and Se are colloidally bonded and can be less bioavailable to plankton. These data can help to establish metal(loid)s levels at the base of the coastal/estuarine food web, at the onset of marine bioaccumulation, and providing information for marine organisms consumed by humans.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H13K1901F
- Keywords:
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- 0478 Pollution: urban;
- regional and global;
- BIOGEOSCIENCESDE: 1803 Anthropogenic effects;
- HYDROLOGYDE: 1879 Watershed;
- HYDROLOGYDE: 4251 Marine pollution;
- OCEANOGRAPHY: GENERAL