Sediment acid volatile sulfide (AVS) was analysed by the diffusion method outlined by Burton et al. 2009, extracting AVS with hydrochloric acid/ascorbic acid and trapping H₂S in an alkaline zinc solution. Chromium reducible sulfides (CRS) was quantified sequentially after AVS analysis, using the method developed by Burton et al. 2008. Sediment organic carbon was analysed, as described by Radabaugh et al. 1994 and Raiswell & Canfield, 2012. After filtration (0.45 µm), reactive iron was measured by spectrophotometry using the 1,10-phenanthroline method (APHA, 2005).