Marine hypoxia: know it.

The basic theory of hypoxic events goes as follows: when deep marine waters upwell to the surface, they bring a large number of nutrients with them, which then stimulate algal blooms. When the algae and bacteria die, they sink to the bottom and are consumed by aerobic bacteria, which flourish and deplete the water's oxygen content. The hypoxic or even anoxic water creates a dead zone -- an underwater desert in which life is literally choked to death.

Natural hypoxic cycles have been documented worldwide, but we're starting to see new areas forming and existing ones being exacerbated. Although previously-developed marine models do predict the creation and expansion of hypoxic zones as a side-effect of global warming (for example, from changes in nutrient-rich riverine ruoff, or through changes in the amount and circulation of arctic water), no one can say for sure if what we're seeing is a genuinely anthropogenic event. Furthermore, although the affected areas are almost entirely cleared of fauna, hypoxic zones serve as buffers between species and can prevent predators from crossing over into prey habitats. Like most aspects of climate change, we are not well-equipped to predict the effects of what we're seeing.