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Thursday
Jun082017

World Oceans Day 2017: How Vulnerable Are The  Oceans?

As water makes up 70% of the planet you’d think it’d be worth protecting. The seemingly slow response to climate change of the world’s oceans can sometimes fool us into thinking they’re doing fine but are in fact just as vulnerable, if not more so, as land or air.

Acidification

One of the most worrying threats oceans face is acidification; a dramatic shift in the chemistry of seawater. The decreasing pH of the oceans has devastating consequences for not only marine life, but all life on Earth, including us.  

The pH lowers as the oceans absorb carbon emissions from the atmosphere, turning them into carbonate ions. While increased levels of carbon can be good for some life, namely photosynthetic algae and phytoplankton, too much is deadly. Ocean acidification, though slight so far, is predicted to cause dramatic changes, as carbonate ions impede the calcification process, stopping coral polyps from constructing their reefs.

Acidification Affecting Pterapod Shells | Wikimedia Commons | NOAA Environmental Visualization Laboratory (EVL) (Impacts of ocean acidification - NOAA) [Public domain]This will also affect shellfish. Studies observed that when exposing Pteropod shells to 2100 projected levels of acidification they decayed after just 45 days. As a major food source for much sea-life Pteropods are at the foundation of oceanic ecosystems, supporting everything from krill to fish to whales. Due to their vulnerability, Pteropods are being used as an indicator for the progression of acidification.

Warming Oceans

Rising sea temperatures cause a range of problems too. Over the past century global ocean temperature has risen by 0.1C, this may not seem like much but the effects are devastating. The first, and most pressing for us, is thermal expansion; the warmer the oceans become the more they expand. Thermal expansion has accounted for half of the total sea level rise over the past century.

It’s not just us that will be affected. Mass ecological disruption will occur as the oceans warm. Warmer sea surface temperature near the equator causes circulation cells of rising warm air which draws in cool air. Subsequent wind patterns push surface water into colder climates. Cooled water is better at absorbing carbon and greenhouse gasses (which is good) but the process makes the water denser. The sinking and upwelling of deep cold water in ocean currents is essential to the circulation of nutrients vital to all life; the denser the water, the slower the current.   

Ocean currents otheriwse known as Thermohaline Circulation | NASAThe world’s oceans are the largest carbon sink on Earth capable of absorbing large quantities but as currents slow down this process will also affect the efficiency of carbon fixation, leaving it to warm the atmosphere instead. A recent study revealed that ocean temperature is rising 13% faster than previously thought so if we’re not careful we could find ourselves in an irreversible cycle of warming.

Much marine life may not be able to cope with the warming, becoming too stressed and dying in waters beyond their climactic tolerance. This would also allow the movement of destructive invasive species into areas previously too cold to venture.

Coral Bleaching

What a typical reef should look like | Wikimedia Commons | U.S. Fish & Wildlife Service - Pacific Region's [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)]Amongst the most susceptible to rising temperature are corals with large-scale coral bleaching events happening around the globe. Bleaching occurs when coral polyps become too stressed from exposure to continual high temperature, ejecting their colourful symbiotic algae on which they rely.

This bleaching has been seen almost everywhere, particularly in the south pacific with several reefs across the South Sea Islands, such as Fiji, as well as reefs around Japan and the Great Barrier Reef all being affected.

Recent years have seen the worst bleaching events ever recorded, with 2016 being one of the most catastrophic. However reefs can sometimes recover if bleaching isn’t too severe. Unfortunately a 2016 study of the Great Barrier Reef, the flagship for coral reef ecosystems, revealed that 95% of the areas surveyed were bleached. Australian environmental experts have now conceded that the Great Barrier Reef is beyond restoration to its original self as a result of 2016’s bleaching events.

Conservation efforts to preserve the ecological significance of the reef continue, though it seems to be fighting a losing battle.

Widespread bleaching | Flickr | Eco Cafe' PhuketProtecting the world’s oceans is key to mitigating the effects of climate change, not just for us but for all life on Earth. Managing our actions on land, lowering our emissions and striving for sustainability, is inherently linked to the fate of the oceans and we should do all in our power to do so.   

By Thomas Phillips - Online Journalism Intern

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