RESUMO
The interactions between the microbial reduction of Fe (III) oxides and sediment geochemistry are poorly understood and mostly unknown for the Louisiana deltaic plain. This study evaluates the potential of P mobilization for this region during bacterially mediated redox reactions. Samples were collected from two wetland habitats (forested wetland ridge, and marsh) characterized by variations in vegetation structure and elevation in the currently prograding Wax Lake Delta (WLD) and two habitats (wetland marsh, and benthic channel) in degrading Barataria Bay in Lake Cataouatche (BLC). Our results show that PO43- mobilization from WLD and BLC habitats were negligible under aerobic condition. Under anaerobic condition, there is a potential for significant release of PO43- from sediment and wetland soils. PO43- release in sediments spiked with Fe reducing bacteria Shewanella putrefaciens (Sp-CN32) were significantly higher in all cases with respect to a control treatment. In Wax Lake delta, PO43- release from sediment spiked with Sp-CN32 increased significantly from 0.064±0.001 to 1.460±0.005µmolg-1 in the ridge and from 0.079±0.007 to 2.407±0.001µmolg-1 in the marsh substrates. In Barataria bay, PO43- release increased from 0.103±0.006µmolg-1 to 0.601±0.008µmolg-1 in the channel and 0.050±0.000 to 0.618±0.026µmolg-1 in marsh substrates. The PO43- release from sediment slurries spiked with Sp-CN32 was higher in the WLD habitats (marsh 30-fold, ridge 22-fold) compared to the BLC habitats (marsh 12-fold, channel 6-fold). The increase in PO43- release was significantly correlated with the Fe bound PO43- in sediments from different habitats but not with their organic matter content. This study contributes to our understanding of the release mechanism of PO43- during bacterial mediated redox reaction in wetland soils undergoing pulsing sediment deposition and loss.