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The assessment of antibiotics mobility under seawater conditions has been rarely studied, as an accurate description of such multicomponent systems is quite challenging. In this study, the adsorption of a widely used quinolone antibiotic in aquaculture, Oxolinic acid (OA), to a synthetic goethite (α-FeOOH) was examined in the presence of major (e.g., Mg 2+ , SO 4 2- ) and trace (e.g., Cu 2+ ) ions naturally occurring in seawater. The OA adsorption can be successfully predicted using a charge distribution multisite complexation model (CD-MUSIC) coupled with the three plane model (TPM). This modeling approach allowed a quantification of the competitive and synergetic effects of different ions in seawater over a large range of environmentally relevant conditions. In addition, the transport of OA in flow-through columns can be well predicted through coupling hydrodynamic parameters and surface complexation constants obtained under seawater conditions. These results may have strong implications for assessment and prediction of the fate of quinolones in sediment-seawater interface systems.

The first chemical investigation of the Mediterranean deep-sea sponge Poecillastra compressa (Bowerbank, 1866) led to the identification of seven new steroidal saponins named poecillastrosides A-G ( 1 - 7 ). All saponins feature an oxidized methyl at C-18 into a primary alcohol or a carboxylic acid. While poecillastrosides A-D ( 1 - 4 ) all contain an exo double bond at C-24 of the side-chain and two osidic residues connected at O-2', poecillastrosides E-G ( 5 - 7 ) are characterized by a cyclopropane on the side-chain and a connection at O-3' between both sugar units. The chemical structures were elucidated through extensive spectroscopic analysis (High-Resolution Mass Spectrometry (HRESIMS), 1D and 2D NMR) and the absolute configurations of the sugar residues were assigned after acidic hydrolysis and cysteine derivatization followed by LC-HRMS analyses. Poecillastrosides D and E, bearing a carboxylic acid at C-18, were shown to exhibit antifungal activity against Aspergillus fumigatus ., Competing Interests: The authors declare no conflict of interest.