Abstract: In alternative embodiments, the invention provides products of manufacture and compositions, e.g., nucleic acid probes, for use as identifying agents or indicators to detect the presence of a hydrocarbon in a sample, e.g., in marine sediments, muds, sands and the like, or in a solution, e.g., an aqueous solution, such as a production water, fresh water, underground water or seawater. In alternative embodiments, the invention provides compositions, e.g., nucleic acid probes or primers or primer pairs, for use as sensors and/or identifying agents to detect the presence of a hydrocarbon in a sample (e.g., in fresh water, underground water or seawater, or a marine mud, sand or sediment), where the presence of the hydrocarbon indicates e.g., the presence of a subsurface oil, petroleum or gas accumulation or deposit. In alternative embodiments, the invention provides compositions and methods for use as tools for offshore oil exploration activities.