To further investigate the relationship between e-SOx activity and carbon metabolism, we conducted two types of sediment manipulations in combination with the two 13C-labelled substrates for PLFA-SIP analysis for both the March and August experiments. For the first manipulation we induced anoxia by depleting the overlying water of oxygen, thus impeding all forms of aerobic sulphide oxidation, including e-SOx (Nielsen et al., 2010). The second treatment involved a horizontal cutting of the sediment with a thin nylon thread (60?μm diameter) that selectively disrupts the e-SOx process by interrupting electron transport by the cable bacteria (Pfeffer et al., 2012). We used two cutting depths: a shallow cut below the oxic zone at 0.3?cm depth and deeper cut in the middle of the suboxic zone at 0.8?cm (see Table 1 for experimental setup). All cores were microprofiled before the experiment and only those cores that showed an e-SOx signature were selected for manipulation. Substrate injections were done as for PLFA-SIP analysis. All treatments were done in duplicate cores.

Table 1 - Total inorganic carbon and propionate incorporation rates calculated from PLFA-SIP analysis from the top 3?cm.

Table 1 - Total inorganic carbon and propionate incorporation rates calculated from PLFA-SIP analysis from the top 3[thinsp]cm - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

Full table