MacDonald et al. (1993 and 1996) have analyzed remote-sensing images from space that reveal the presence of oil slicks across the north-central Gulf of Mexico. Results confirmed extensive natural oil seepage in the Gulf of Mexico, especially in water depths greater than 1,000 m (3,281 ft). A total of 58 additional potential locations were documented where seafloor sources were capable of producing perennial oil slicks (MacDonald et al., 1996). Estimated seepage rates ranged from to compared to less than for ship discharges (both normalized for 1,000 mi2 (640,000 ac)). This evidence considerably increases the area where chemosynthetic communities dependent on hydrocarbon seepage may be expected.