In addition to warming and acidification, the decline in oxygen levels in the oceans also leads to changes in marine life, chemical and physical balance. The results were published in a report by the International Union for Conservation of Nature (IUCN) to the United Nations Climate Change Conference in Madrid. There is no life without oxygen, even in the sea. At present, in many seas, the oxygen content of seawater is decreasing continuously, resulting in increasingly limited living space for marine life, which may have fatal consequences for fisheries and marine economies in the future.
Since the reduction in sea water oxygen is largely driven by global warming, the IUCN report is another “wake-up call” for participants at the World Climate Change Conference in Madrid.
In addition to global warming, the report shows other causes of oxygen reduction, including over-fertilization in coastal waters and changes in ocean circulation. “Because of global warming, warmer water absorbs less oxygen, affecting the transmission of oxygen from the surface of the water to the depths of the ocean,” said Luther Strama, an oceanographer at the Kiel Marine Research Centre in Germany. “In a paper by Kiel oceanographer Sank Schmidtko on the geochemical interactions of climate in the tropical oceans, it is evidencethat that global seawater oxygen levels have fallen by more than 2% over the past 50 years.
The IUCN report also makes it clear that oxygen losses vary widely from sea to sea, and that while oxygen levels in some areas of the ocean remain virtually unchanged, the evolution of others is clearer, especially in coastal waters. In addition, a large amount of fertilizer-containing materials flowing into the sea, as well as offshore aquaculture, are conducive to the growth of algae, will consume more oxygen in the sea. Andris O’Hillis of the Kiel Marine Research Centre says the impact is already evident in the world’s most resource-rich waters, such as Peru and West Africa.