The Ocean’s Biggest Killer Hides in Plain Sight


The ocean’s biggest killer hides in plain sight

We all know plastic is bad. But there’s a greater threat to our oceans — and almost no one ever sees it. There is a crisis in our oceans. But it’s not the one you imagine. When people think of the ocean in danger, they usually picture pollution by plastics, and the horror-show of vivid images that comes with it. The whale which starved to death because its stomachs was filled with plastic bags. The baby albatross fed coloured plastic by its parents. The turtle rescued with a straw up its nose. 

Shocking images like these have captured the world’s imagination and triggered its collective guilt. We use plastics every day, and so we understand our direct and tangible connection to the problem. As a result we see that we can also be part of the solution. The effects on sea life of single-use plastic have a grotesque quality that has sparked concerted action around the world to wean ourselves off it.

This response is unquestionably a good thing. Yet horrific though plastic may be, there are other issues destroying the health of the ocean that are harder to capture through images, but which pose an even greater threat to the sea, and to life on earth. It is to make these threats more widely recognized — and to drive concrete action to reverse them — that conservation charity Blue Marine Foundation was founded in 2010. 

‘Ghost’ fishing gear makes up around 10% of ocean macro-plastic but kills four times more marine life than the other 90 percent.

Burning coal is dissolving shells

One of the biggest threats to the health of the ocean is climate change and its related ugly sibling, acidification. Without the ocean, the Earth would be at least 36 degrees warmer by now. Rising temperatures are not only killing corals, which support around a quarter of ocean biodiversity, they are impacting the way the ocean regulates our climate. As the amount of carbon dioxide in the atmosphere increases, the amount of carbon dioxide absorbed by the ocean rises too. This is leading to a series of chemical reactions in sea water — acidification — that has a disastrous impact below the surface, in particular dissolving the shells of many sea creatures. 

Alongside this threat is de-oxygenation. The ocean provides half of Earth’s oxygen, but it is losing its capacity to do so, because of what are called ‘anoxic zones’. These are areas of water that are depleted of dissolved oxygen, caused by nitrates that come from sewage as well as contaminated water that has drained into the sea from agricultural land. 

Ocean noise and invasive species are two other problems which are having a serious impact on marine life. Noise from busy shipping lanes confuses marine mammals and fish who use sound to communicate and breed, while the accidental transportation of the venomous lionfish in ships from its native Red Sea to the Mediterranean and the Caribbean is having a terrible impact on native species. The population of these aggressive predators has ballooned in secure reef areas, forcing native species out to dangerous waters.


Trawling — more CO2 than the entire aviation industry

But arguably the greatest threat of all, because it reduces resilience to all the others, contributes to climate change and is taking food from those who rely on fish as their main source of protein — is overfishing. Overfishing strips the ocean of life, and has driven whole species to the brink of extinction, with 90% of large fish already gone. Biodiversity is under threat from ‘bycatch’, the name given to the large amounts of sea life that is unintentionally caught and then often discarded (often dead or dying) in the trawling process. Overfishing disrupts entire ecosystems. For example, the reason there are so many jellyfish is because its predators, such as tuna and sea turtles, have seen such declines.

Why does this matter so much? Because of the link between ocean habitats and climate change. Industrial-scale fishing harms habitats, in particular bottom trawling, which ploughs up the seabed – breeding grounds for fish, but also vital habitats for absorbing carbon. Carbon is stored in the seabed itself.  Seagrass absorbs carbon 35 times faster than tropical rainforests.  It is estimated that bottom trawling the world over releases as much CO2 into the atmosphere as the entire aviation industry. This is a staggering figure that receives virtually no attention. Think what could be achieved if trawling were reduced.

Tackling overfishing is the main focus of Blue Marine which has placed over four million square kilometres of ocean under protection and is working daily to draw the world’s attention to this serious yet solvable problem.

The deadly spectre of ‘ghost gear’

Consumer waste is undoubtedly wrecking our oceans, but again, there is a little-mentioned aspect of plastic waste which is abandoned fishing gear.  ‘Ghost gear’ is the name given to fishing equipment lost or abandoned at sea. It makes up around 10% of ocean plastic but kills four times as much marine life as the other 90%, because it is designed for that purpose. FADs (fishing aggregating devices) float through the ocean drawing in schools of tuna but are often abandoned and get trapped on coral reefs, damaging fragile habitats and entangling turtles and sharks. Around the Aeolian Islands, north of Sicily, Blue Marine has found ghost nets that have caught hundreds of rare and beautiful fish, and become weighed down with their dead bodies. They sink to the bottom, the fish rot and the net rises, only to begin the ghastly process once more.

Why is it that the public care so much about plastic but are largely unmoved by overfishing?  My theory is that plastic is so shockingly out of place in the context of ocean life. When people see the seahorse with its tail wrapped round an earbud, or the seal trapped in the plastic bag, the juxtaposition is startling. And at the same time, these shocking images have a sense of the horribly familiar: ‘that could have been my earbud, my shopping bag…’ By contrast, fishing is a sanctioned activity, done away from the public gaze by fishing vessels. Their work may amount to nothing less than marine massacre, but somehow it is what we expect to happen in the sea because it has been taking place for millennia.

The challenge for charities such as Blue Marine is that people have little affinity with fish because they are not cute or cuddly. Until the 2020 Netflix documentary ‘My Octopus Teacher’, most people had no sense of smaller sea creatures having feelings or intelligence – they were just seen as food. Mammals such as whales or dolphins fare better. For humans, there is a hierarchy of affinity: the more intelligent, the more worth saving. We care deeply for dolphins and whales at Blue Marine, but we also work to save creatures such as oysters, eels, cuttlefish and whelks, and all the ocean’s other less glamorous inhabitants.


Local, plentiful, sustainably caught, and in season

The call to action for plastic reduction is simpler.  Not using a plastic bag and giving up using straws (something we should surely have done when we were 5 years old!) is easy to do. But if you eat fish, it’s hard to give it up. Some say that’s the only solution, but Blue Marine’s message is a more nuanced one. If you are a pescatarian, only eat fish that is local, plentiful, sustainably caught, and in season. It’s true that this is complicated. As is explaining the link between overfishing and climate change, and that’s why we have created this site: 

At Blue Marine, tackling plastic is not our particular focus, but we see it as the gateway to understanding the crisis in the ocean. People are drawn in via a beach clean, or because they’ve seen an image of plastic pollution. But once they start to understand the problems, they realise that there are even greater actions we need to take to restore the ocean to health. If we’re right, you may already have already been shocked by plastic pollution into thinking about the state of your ocean. You may have cut back on your use of plastics. This is a fantastic first step towards the transformation we need in our relationship with the resource on which we all depend.

But there is much more that can be done. If you’d like to find out more about the work of Blue Marine, about ocean conservation and climate change, and the battle against overfishing, please follow our socials or visit our website. To borrow a phrase: the world is your oyster.

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