## 3 Results
### Experiment 4 (A Supplementary Addition of Inorganic Electron Acceptors)  
The addition of inorganic electron acceptors (nitrate and oxidized iron) in order to enhance anaerobic respiratory processes other than sulfate reduction and methanogenesis, not only did not improve the performance of the standard BAP dose (50 g/m\({}^{3}\) dose) in reducing the organic matter content, but instead blurred its effect. Thus, even when BAP was added together with the respective electron acceptor, no differences were found with the values of the organic matter variables of the controls (\(p\)-values \(>\) 0.05), whereas all treatments gave significantly higher OM values than those of the standard dose without amendments (\(p\)-values \(<\) 0.05 or \(p\)-values \(<\) 0.001 depending on the variable). Such way, these additions clearly difficult the positive effect of the BAP for organic matter degradation. The main significant changes promoted by the treatments made in this experiment were related to the increase of nitrite in the treatment with KNO\({}_{3}\) addition (Figure 4), increasing by one order of magnitude (until 1.2 ug/g dw), compared to both the non-amended controls (\(p\)-value = 0.003) and the standard dose of BAP (\(p\)-value \(<\) 0.001).  
Experiment 5 (Assessing the Role of Acetoclastic Metabelisms, Sulfate Reduction, and Methanogenesis)  
The addition of acetate as substrate for the acetoclastic metabolism improved the performance of the standard dose of BAP in reducing the organic content of the assayed sediments (Figure 3). When acetate was added, the %OM and COD decreased by 35.0% and 22.7%, respectively, both yielding significantly higher decreases (\(p\)-values \(\leq\) 0.01) compared to the control and even, a significantly higher %OM decrease (\(p\)-value \(<\) 0.001) compared to the standard BAP (50 g/m\({}^{3}\)) dose. These reductions were the highest observed in the whole study. Contrastingly, all OM-related parameters increased comparedto the control, though not achieving statistical significance, when the BAP was supplemented either with the inhibitors BES or with molybdate. Moreover, these amendments even showed significantly higher values of the organic matter variables compared to the standard dose treatment (\(p\)-values \(\leq\) 0.01). These responses indicate that inhibition of either methanogens or sulfate-reducing bacteria affected notably the performance of the BAP treatment, but also that they difficult the already existing anaerobic respiratory processes through these pathways.  
Although none of the treatments showed any statistically significant difference in TN compared to the controls and the standard BAP dosage, a noticeable significant reduction (\(p\)-values \(\leq\) 0.003) of around 70% of the ammonium content in the sediments compared to the control and standard was observed when the acetate amended to the standard BAP treatment was compared to all the other treatments, or even higher when BES was added (Figure 4). Moreover, for the BES amended treatment, a concomitant increase in nitrite was significant compared to both the control and the standard BAP dosage. Contrarily, in the molybdate amended treatment, the ammonium increased compared to both the control and the standard BAP dose, whereas nitrite was significantly lower than in the control for this treatment. Concerning phosphorus, TP concentration showed the highest (\(\sim\) 50%) and highly significant (\(p\)-values \(\leq\) 0.001) decreases when the BAP was supplemented with acetate compared to both the control and the standard BAP dose treatments (Figure 4). The BES amended treatment showed a similar behavior. The increases in loosely-binding P, though not statistically significant for all comparisons in this experiment, may show that the decreases in TP can be explained by a higher P-mobilization capacity induced by the BAP, as also shown by the rest of experiments.