An organic chemical compound of hydrogen and carbon in the gaseous, liquid, or solid phase.

The molecular structure of hydrocarbon compounds varies from the simplest (methane, a constituent of natural gas) to the very heavy and very complex.

Areas where hydrocarbons seep slowly from the sea floor, and which may be associated with specific faunal compositions.

Marine hydrocarbon seeps are cold as distinguished from volcanic, hot seeps; and have two major sources, biogenic or bacterial production of gas, and petrogenic or thermogenic (relating to subsurface petroleum reservoirs) that "leak" to the surface.