Evaluation of different bioremediation protocols to enhance decomposition of organic polymers in harbour sediments

The response of the microbial community (in term of abundance and enzymatic activity) was investigated to test the effect of different bioremediation protocols to naturally enhance decomposition of organic polymers in harbour sediments (Genoa Harbour, Italy, N–W Mediterranean). Bioremediation techniques tested were bioaugmentation (5 different microorganisms' inocula), biostimulation (air supply), and natural attenuation. The coupling bioaugmentation/biostimulation was also tested. After 60 days, following the bioaugmentation protocol, bacterial densities correlated to the quantities of inocula amended to the boxes, suggesting that allochthonous community was able to survive and multiply. However, while bioaugmentation alone seems not to be able to carry out significative degradation, its coupling with air insufflations produced the best response: here bacterial densities increased, especially in the water (from 2.3 · 107 to 3.50 · 108 cells ml)1), average cell size and enzymatic activities increased, and sedimentary organic matter was significantly depleted (PRT 5-folds reduction, CHO 1.5-folds reduction). The strong coupling observed between the sediment and water compartments together with the greatest microbial response observed in this latter suggest that the sediment–water interface may constitute a key compartment for the occurring of biodegradation processes in organic-rich sediments.