GREEN
06/03/2011 01:04 pm ET | Updated Aug 03, 2011

In Gulf Dead Zone, Female Fish Develop 'Testes'

The Gulf dead zone occurs when agricultural and waste runoff from the Mississippi River spark blooms of algae and microbes. These organisms gobble up oxygen, starving other marine life and creating huge swaths of "dead" ocean.

Between 2006 and 2007, nearly a quarter of female Atlantic croaker fish caught in the northern Gulf's dead zone had developed deformed, testes-like organs instead of ovaries.

Read more on National Geographic