The hydrogen sulfide layer in the Black Sea extends from about how many feet below the surface?

The hydrogen sulfide layer in the Black Sea typically begins at about 200 feet below the surface. This phenomenon occurs because the Black Sea has a unique stratification due to its limited exchange with ocean water and the presence of high levels of organic material that consume oxygen. As you go deeper, the anoxic (oxygen-free) conditions develop, leading to the formation of hydrogen sulfide, a toxic compound. The 200-foot mark is significant because it marks the transition from aerobic conditions, where marine life can thrive, to anaerobic conditions, where typical aquatic life cannot survive.

This aspect of the Black Sea's ecology highlights the effects of stratification and the importance of depth in aquatic systems, providing insights into how different environmental layers can exist in the same body of water.