Low oxygen levels, which have been found along south-eastern
Australia, are known to increase stress on fish. (Reuters: Ho New)Scientists fear mass extinction as oceans choke - ABC News (Australian Broadcasting Corporation): "Australian scientists fear the planet is on the brink of another mass extinction as ocean dead zones continue to grow in size and number.
More than 400 ocean dead zones - areas so low in oxygen that sea life cannot survive - have been reported by oceanographers around the world between 2000 and 2008.
That is compared with 300 in the 1990s and 120 in the 1980s."