Diary 159: Lesser fish in the future?

Dead fish on sea surface is now a matter of concern.

Ocean surface is regarded hypoxic – oxygen levels are lower than 1.43 millilitres per litre, so low that fish can’t survive.

Ocean surface water normally contain 5-8 millilitres of oxygen per litre of water.
Around the globe, many Oxygen Minimum Zone (OMZ) are losing oxygen and expanding horizontally and vertically.

OMZs curreently cover about 30 million square kilometers, or 8% of the ocean area.
What are the possible causes of hypoxia?

Possible cause 1: Agricultural fertilizers leaking into the ocean. The excess nutrients fuel plankton blooms, which consume oxygen.

Possible cause: global warming? No strong evidence yet.

(Source of information: Virginia Gewin, 2010. “Dead in the water”. Nature 466: 812-814.)