The chemically and biologically induced
changes in the composition of a polluting petroleum
hydrocarbon mixture are known collectively
as weathering. Microbial degradation
plays a major role in the weathering process.
Biodegradation of petroleum in natural ecosystems
is complex. The evolution of the hydrocarbon mixture depends on the nature of the oil, on
the nature of the microbial community, and on
a variety of environmental factors which influence
microbial activities.