Microbial mediated sedimentary phosphorus mobilization in emerging and eroding wetlands of coastal Louisiana.

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 PO mobilization from WLD and BLC habitats were negligible under aerobic condition. Under anaerobic condition, there is a potential for significant release of PO from sediment and wetland soils. PO 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, PO release from sediment spiked with Sp-CN32 increased significantly from 0.064±0.001 to 1.460±0.005μmolg in the ridge and from 0.079±0.007 to 2.407±0.001μmolg in the marsh substrates. In Barataria bay, PO release increased from 0.103±0.006μmolg to 0.601±0.008μmolg in the channel and 0.050±0.000 to 0.618±0.026μmolg in marsh substrates. The PO 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 PO release was significantly correlated with the Fe bound PO in sediments from different habitats but not with their organic matter content. This study contributes to our understanding of the release mechanism of PO during bacterial mediated redox reaction in wetland soils undergoing pulsing sediment deposition and loss.