Climate change, nutrient pollution driving oxygen from oceans; threaten fish species

A  study by conservation group IUCN has revealed that climate change and nutrient pollution are reducing oxygen from our oceans and threatening many species of fish.  As per report, around 700 ocean sites are w suffering from low oxygen, compared with 45 in 1960s. Aquatic species including tuna, marlin, and sharks are at stake with depletion. Nitrogen and phosphorus from farms and industry discarded in sea waters form major portion of nutrient ruffs. Yet climate change poses a higher threat than ruff in recent days.

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Aquatic species at threat due to Climate Change

Global warming i.e. increase in carbon emission enhancing greenhouse effect les to a higher temperature and much of heat is absorbed by oceans. This warmer water holds less oxygen and scientists estimate that between 1960 and 2010, amount of gas dissolved in oceans declined by 2 per cent. depletion is concentrated in many tropical locations with losses upto 40 per cent. Waters with less oxygen favour species such as jellyfish, but is b for fast-swimming species like tuna. Minna Epps from IUCN told media that y h earlier kwn about phemen of de-oxygenation but were t aware of links to climate change. decline of oxygen qurupled in past 50 years, she quoted. According to authors, bigger fishes with more energy needs will have to move to shallow waters where more gas is dissolved. Yet this will make species much more vulnerable to over-fishing. 

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Oxygen depletion will also affect cycling of elements

world's oceans are expected to lose 3-4 per cent of ir oxygen by year 2100 if emissions are t controlled. In tropics, more loss is expected in top 1,000 metres of water column, which is richest in biodiversity. Moreover, depletion of oxygen is also b for basic processes like cycling of elements crucial for life on Earth, including nitrogen and phosphorous. Minna Epps said that running out of oxygen would mean habitat loss and biodiversity loss and a slippery slope down to slime and more jellyfish. It will also change energy and biochemical cycling in oceans, she ded.

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