Final answer:
Bioremediation is the use of organisms to neutralize or remove pollutants from the environment, with applications including in situ and ex situ methods and the cleanup of oil spills and removal of toxic metals like mercury.
Step-by-step explanation:
The biological process occurring naturally in which an ecosystem removes contaminants is best described by bioremediation. Bioremediation involves the use of living organisms, such as bacteria, plants, and fungi, to neutralize or remove pollutants from a contaminated site. Through natural metabolic processes, these organisms can break down hazardous substances into less toxic or non-toxic substances.
In situ bioremediation is conducted at the site of contamination without the need to remove the contaminated material, while ex situ bioremediation involves treating the contaminants at a different location. One of the most well-known applications of bioremediation is the cleanup of oil spills, whereby naturally occurring or genetically engineered oil-degrading bacteria consume and break down oil into harmless compounds.
Moreover, bioremediation can be utilized to remove toxic metals like mercury from the environment, as certain bacteria have the capability to transform toxic mercury into less harmful forms.