Plastic is only the beginning

Our oceans cover 70 per cent of our planet's surface and host the largest contiguous ecosystem on Earth, featuring immense biodiversity, much of which remains unexplored, particularly in the deep sea. The oceans produce more oxygen than all rainforests combined and stabilise the climate by sequestering greenhouse gases. They contain critical raw materials, serve as transport routes for international trade, provide food and energy for coastal populations, and offer space for settlements and recreation. Many of the world's largest megacities are located on coastlines. Thus, humanity exploits the resources the ocean provides, but what do we offer in return? We inflict wounds upon the marine ecosystem through our careless and reckless lifestyle. Under increasing stress, the ocean groans under the burden of climate change and anthropogenic pollution, caused by the only species on Earth that generates waste.

Mountains of waste, which frequently pile up along coastlines, present an obvious problem; a visible issue that commands attention and prompts a search for solutions. However, much of the pollution does not end up as a visible pile of rubbish on our doorsteps, for example:

• Nitrates and phosphates from industrial agriculture, livestock farming, and intensive arable cultivation.

• Chemicals and heavy metals from industrial wastewater, atmospheric emissions, mining, and oil combustion.

• Radioactivity from nuclear power plants operated by the USA, Russia, Japan, and European states.

• Oil pollution from wastewater, leakages during oil extraction, tanker accidents, and oil platforms [Source 12].

• Munitions in the sea originating from World Wars and other conflicts.

• Noise and acoustics from deep-sea mining, maritime transport, military activities, the driving of sheet piles for ports and piles for offshore installations, exploration for oil and gas reserves using seismic airguns, and oil and gas extraction.

• Plastic waste, of which approximately 20% originates at sea and about 80% on land [Source 13]. Ocean currents distribute this waste across the seas. Five major garbage patches are known. However, most of the debris ends up on global coastlines. Plastic waste also includes discarded fishing nets, known as ghost nets, left behind in the oceans.

Plastic in the ocean

Estimates suggest that 86 million tonnes of plastic have entered the oceans to date due to human activity. Approximately 10 million tonnes are added each year [Sources 15-16].

Plastic waste entering the ocean via rivers causes the death of marine animals. Whether a seal slowly suffocates from a plastic ring around its neck, a whale ingests plastic, or a turtle mistakes plastic bags for jellyfish, eats them, and perishes, the dilemma stems from our endless plastic consumption and the ghost nets left by fisheries. Northern gannets on Heligoland now build nearly 90% of their nests using fishing nets. The fledglings become entangled in them and suffer a miserable death. Global industrial fishing further compounds the issue. A fleet of 4.5 million fishing vessels with 40 million fishers on board exerts relentless pressure on fish stocks in our global oceans [Source 17].

Nothing we discard is ever truly "gone". This is especially true for plastic that ends up in the sea. This realisation only slowly seems to register with many people, as countless fishing gears from industrial fleets still disappear into the depths of our oceans every year. From continental shelves to deep-sea basins, Portuguese and Spanish researchers surveyed European waters for plastic debris and published their findings in a study [Source 18]: it was found everywhere. The highest concentrations of plastic were located in deep-sea trenches, areas otherwise remote from human reach. Lost nets accounted for more than a third of the total waste. In the Baltic Sea alone, between 5 and 10 thousand nets go overboard each year [Source 19].

Once lost, these nets act as drifting death traps. The duration for which they continue to catch marine life is not yet fully understood and depends on environmental factors, such as how quickly a net becomes colonised by algae, sponges, and crustaceans to the point where it virtually merges with its surroundings. Estimates suggest it can take up to 27 months before a net is rendered harmless by the growth of sessile organisms [Source 20].

Currently, more than 500 animal species are threatened by this entanglement issue. Fully 83% of North Atlantic right whales (Eubalaena glacialis) carry plastic debris on their bodies, and many individuals of all 7 existing marine turtle species become entangled in ghost nets, where they suffocate miserably alongside whales, seals, and sharks [Source 20]. Where the nets do not kill immediately, they severely restrict mobility or prevent feeding. Since plastic does not biodegrade but is merely abraded over time, it breaks down into individual fibres and microplastics. Even then, the mortality does not cease: microplastics fill the stomachs of the smallest organisms at the base of the food chain, and seabirds, including the northern gannets of Heligoland, unwittingly collect the brightly coloured fibres to build their nests. This decoration has already cost the lives of many seabird chicks on the sheer cliffs. Upon closer inspection, hundreds of carcasses hang from the red cliffs like macabre figureheads.

Fortunately, global efforts exist to retrieve these uncontrolled killing instruments. These include the Olive Ridley Project in the Maldives, initiatives by the Norwegian government since 2018 [Source 21], and numerous WWF projects in our domestic North and Baltic Seas. Many recreational divers also report or salvage ghost nets during their dives.

Of course, it would be far better if these nets never had to be retrieved in the first place.

Consequences of marine waste

Through industrial, conventional agriculture, massive quantities of phosphorus and nitrogen compounds enter the sea via rivers. This eutrophication stimulates algal blooms, leading to the formation of so-called dead zones. A prime example of this is the Baltic Sea.

Due to industrial wastewater, atmospheric emissions, mining, and oil combustion, the threat lies not only in the volume and diversity of pollutants entering the ocean—which can destroy entire marine ecosystems for decades—but also in the bioaccumulation of specific substances, such as mercury, within the food chain.

The ocean has been used not only as a testing ground for over 250 nuclear weapons tests but also, from 1946 to 1993, as a massive dumping ground for radioactive waste stored in metal drums. These drums can be found in all oceans, where they rust and release radioactive radiation. Although the disposal of solid radioactive waste was banned in 1993 under the London Convention (LC72), the direct discharge of liquid radioactive waste remains permitted and is still practiced. Even in small quantities, radioactive radiation carries an increased risk of cancer [Sources 22-24].

Globally, 99.8 million barrels of oil were consumed per day in 2018. Over the past 50 years, global oil consumption has nearly tripled [Source 25].

One of the worst disasters in oil extraction occurred on 20 April 2010. The "Deepwater Horizon" drilling rig, operated by the British oil company BP, exploded in the Gulf of Mexico. Eleven people died, and oil leaked uncontrollably into the sea from the damaged wellhead. Estimates place the spill at 780 million litres. It contaminated a 75-kilometre stretch of coastline, causing the deaths of thousands of birds, marine mammals, fish, and other marine organisms. Additionally, 40,000 people lost their livelihoods as a result of the disaster. Tanker accidents are no less devastating. The recovery period for nature following an oil spill varies between a few months and 20 years, depending on the ecosystem and soil characteristics [Sources 25-26].

Toxic and explosive legacy munitions lie by the tonne on our seabeds, posing a hazard to humans, animals, and the environment. Much of this waste was simply dumped there after the war. Accidents could occur during the construction of offshore wind farms or the laying of submarine cables. As bombs and munitions corrode, toxic and carcinogenic substances are increasingly released into the environment, potentially entering the human food chain in dissolved form or as microparticles [Source 27].

Due to the steadily increasing noise levels in our oceans, all marine organisms are affected. Negative impacts include behavioural changes, altered migration routes, displacement from habitats, hearing damage, malformations, communication difficulties (masked by ambient noise), and death, depending on the noise level and the severity of the stress response [Sources 28-29].