By Sreerekha Pillai.

The sinking of a chemical-laden ship off Sri Lankan coast this week, setting plastic afloat and with chances of a possible oil spill, could turn out to be one of the worst marine disasters in our backyard. Climate change, pollution, oil and gas extraction, coastal construction, and overfishing are damaging the oceans, which cover 70 per cent of the earth and constitute 94 per cent of life on the earth.

Oceans have been anchoring life not just under water but also on terra firma. Marine plants produce almost 70 per cent of oxygen. A recent study in the journal Frontiers in Plant Science has found that diatoms — the microscopic plants that float on the surface of the ocean — absorb almost 10–20 billion tonnes of carbon dioxide (CO2) annually. This is equivalent to the amount of CO2 captured by all of the world’s rainforests. Similarly, seagrass accounts for almost 10 per cent of the oceans’ capacity to absorb carbon.

That is not all. Over their lifetime, the mighty whales amass 33 tonnes of CO2 on an average. And when they die, they sink to the seabed, trapping the carbon for years together.

Trouble under water

Indeed, oceans are the lungs of the planet. But global warming and climate change, driven by human activities, are sounding the death knell for many aquatic life forms.

The ‘dead zones’ in the ocean, where lack of oxygen incapacitates life, are swelling. With a recent study in the Science claiming that the oceans absorb almost one-third of global carbon dioxide emissions, it comes as no surprise that the sea surface temperature is rising. This turns the water acidic, bleaches and reduces coral reefs to rubble, and forces fish to migrate from the equator to the poles, in search of comforting cooler conditions. It is being estimated that the average surface temperature of seas due to warming has risen by approximately 0.13 degree Celsius every decade over the last century.

The rise in sea temperatures has hit the coral reefs — from the Bahamas to the Great Barrier Reef — the hardest. The rich diversity of life housed by reefs makes them the ‘rainforests of the sea’. Researchers, however, are pointing out that almost 30 per cent to 50 per cent of reefs have been lost in the last 40 years with the likelihood of most of the remaining reefs disintegrating in the coming decades.

When temperature rises, corals force microscopic algae (that they co-exist with) out, getting bleached in the process. Algae not just produce food for corals but also lend them vibrant colours. Bereft of the algae, corals become susceptible to disease, knocking down the ecosystem that hosts almost a quarter of the known aquatic species.

Sustaining livelihoods too

Changes in the oceanic biosphere may also turn the tide of blue economy. With a coastline spread over 7,500 kilometers, India currently has a thriving blue economy, which rests on fishing, shipping, tourism, deep-sea mining, and offshore energy resources among others. The oceans also support 95 per cent of the country’s business through transportation.

Research on sustainable ocean economy shows that every dollar invested in key ocean activities such as restoring mangroves, decarbonising international shipping, and increasing sustainable seafood production can yield five dollars or more in return.

Well, if we don’t start thinking blue, not just livelihoods but life itself will be at stake.

The author is Chief Editor at CSTEP.

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