Some conditions can cause the absence of OAE's. These include: cysts, external otitis (swimmer's ear for example), stenosis, or abnormal middle ear pressure, a perforated ear drum, otosclerosis, cholesteatoma.
The Gulf of Mexico (Spanish: Golfo de MÃ©xico) is an ocean basin largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba.
Photo courtesy of NOAA. The Gulf of Mexico dead zone is an area of hypoxic (link to USGS definition) (less than 2 ppm dissolved oxygen) waters at the mouth of the Mississippi River. Its area varies in size, but can cover up to 6,000-7,000 square miles. The zone occurs between the inner and mid-continental shelf in the northern Gulf of Mexico, beginning at the Mississippi River delta and extending westward to the upper Texas coast.