Bioremediation techniques for hydrocarbons in coastal marine systems

Hydrocarbons are among the most abundant contaminants in coastal marine systems. Many coastal areas around the world are subject to chronic inputs of these compounds, sometimes on a massive scale (oil spills). Their dynamics in the environment are complex, involving numerous interacting abiotic and biotic processes. Among these, hydrocarbon biodegradation, carried out by microorganisms sometimes specialized in their use (known as "hydrocarbonoclasts"), enables their effective elimination under oxic and anoxic conditions, both in seawater and in sediments. It can be used in a wide range of physico-chemical conditions of temperature, pH and salinity. This makes it a process of choice for ecological engineering to clean up (bioremediate) marine ecosystems polluted by hydrocarbons. The various bioremediation strategies aim to stimulate (biostimulate) the natural catabolic capacities of the microbial community indigenous to the polluted coastal environment. Stimulation can be achieved by adding nutrients (fertilizers), (bio)surfactants, terminal electron acceptors (e.g. O ₂ , $N{O}_3^{-})$ or through electrochemical processes (electrostimulation). Another strategy may involve introducing into the polluted medium hydrocarbonoclast strains/mixed cultures chosen for their hydrocarbon-degrading capabilities (bioaugmentation) and which may have been isolated from the same medium. Several of these strategies can also be combined (e.g. combined addition of fertilizers and biosurfactants).