Through some hard-core detective work and astute observations, Dr. Bakun and his colleague, Dr. Scarla Weeks of the University of Cape Town in South Africa, realized that the rampant overfishing of sardines off the southwest coast of Africa may have been a factor in eruptions of two toxic gases – hydrogen sulfide, and methane – from the Atlantic Ocean floor. The hydrogen sulfide causes a horrible rotten-egg smell that had long burdened (and perplexed) residents of local communities in Namibia, while also poisoning fish and causing oxygen poor dead-zones in the water. Methane gas traps 21 times as much heat as carbon dioxide, the most common greenhouse gas.
Drs. Bakun and Weeks co-authored a 2004 scientific paper in the peer-reviewed journal Ecology Letters describing their theory that sardines, phytoplankton, and climate change are intricately connected. When plentiful, sardines consume massive quantities of tiny plants called phytoplankton, which float atop the ocean and are whisked to the surface by the “upwelling” of subsurface waters. (The ocean off Namibia is one of the world’s strongest upwelling regions in the world). But when sardines are overfished, phytoplankton continue to blanket the ocean until they die and sink to the ocean floor, where they are decomposed by bacteria. These bacteria produce massive amounts of toxic gases in the process – gases that are even worse for global warming than carbon dioxide and turn this stretch of the African coastline into a marine life dead zone.
The cyclical causes and effects of these and other seemingly unrelated events affecting the world’s water supply are chronicled in two new hours of "Strange Days on Planet Earth," narrated by actor and environmentalist Edward Norton. The acclaimed National Geographic series, now in its second season, was shot on location around the world with teams of scientists in action.
http://www.pewoceanscience.org/press/press-article.php?ID=89i was watching this on the netflix the other night... the gas eruptions were large (1000s of kilometers) which can be seen from orbit.