Total organic carbon analyser

Analyses of the total Sn in sediments were performed by the method described in Sondi et al. (2017) , using high resolution inductively coupled plasma mass spectrometry (HR ICP-MS; Element 2, Thermo Finnigan). Briefly, sediments were digested in the microwave oven (Multiwave 3000, Anton Paar) by two-step total digestion procedure; I step: HNO 3 (65% p.a.) + HCl (36% s.p.) + HF (48% s.p.), and II step: H 3 BO 3 (40 g L -1 ). The quality control was performed by the simultaneous measurements of the certified reference materials for marine sediment (MESS-3, NRC, Canada), for which satisfactory results were obtained.
2.6. Total organic carbon (TOC) and the grain size analyses of sediment samples TOC analyses were performed by the high-temperature catalytic oxidation (HTCO) method with non-dispersive infrared (NDIR) detection on the solid sample module SSM-5000A connected with TOC-V CPH Shimadzu total organic carbon analyser. The inorganic carbonate fraction was removed with 2M HCl, followed by drying at 50°C overnight. The grain size analyses were performed using a laser diffraction particle size analyser LS 13320 (Beckman-Coulter, USA).

The determination of DOC, protein, and polysaccharide concentrations in SB EPS, LB EPS, and TB EPS were based on the methods described by Li et al. (2016) . Briefly, DOC was determined with a total organic carbon analyser (Shimadzu, Japan). Total polysaccharide
concentration was measured with phenol-sulphuric acid method (Dubois et al., 1956) . Protein concentrations were measured with the modified Lowry method (Frølund et al., 1995) .