Plastic is only the beginning

Our oceans cover 70 percent of our planet's surface and host the largest contiguous ecosystem on Earth, featuring immense biological diversity, 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 situated on coastlines. Human population thus exploits the provisions offered by the ocean, but what is given in return? We inflict wounds upon the marine ecosystem through a careless and reckless lifestyle. Increasingly stressed, the ocean groans under the burden of anthropogenic climate change and environmental pollution from humans—the only living organisms on Earth that generate waste.

Mountains of waste, which frequently accumulate on coastlines, present a problem for everyone, or at least for the majority; a visible issue that prompts concern and a search for solutions. However, much of the pollution does not end up as a visible mountain of waste on our doorsteps, for example:

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

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

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

• Oil pollution from domestic and industrial runoff, leaks during oil extraction, tanker accidents, and oil platforms [Source 12].

• Munitions in the sea outstanding from world wars and other conflicts.

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

• Plastic pollution, with approximately 20% originating at sea and about 80% from land-based sources [Source 13]. Currents distribute this waste throughout the oceans. Five major garbage patches are documented. However, the majority of the waste accumulates on global coastlines. Plastic waste also includes discarded fishing nets, known as ghost nets, which are abandoned in the oceans.

Plastic in the ocean

Estimates indicate that anthropogenic activities have introduced 86 million tonnes of plastic into the oceans to date. Approximately 10 million tonnes are added annually [Sources 15-16].

Plastic waste entering the ocean via rivers leads to animal mortality. Whether a seal slowly suffocates from a plastic ring around its neck, a whale ingests plastic, or a turtle mistakes plastic bags for jellyfish, consumes them, and dies, the dilemma remains our relentless consumption of plastic and the ghost nets abandoned by commercial fisheries. The Northern Gannets (Morus bassanus) on Helgoland now construct nearly 90% of their nests from fishing nets. Juvenile birds become entangled in these nets and perish miserably. Global industrial fishing further compounds this issue. A fleet of 4.5 million fishing vessels carrying 40 million fishers continuously exerts immense pressure on global fish stocks [Source 17].

Nothing discarded is ever truly "gone". This is particularly true for plastic that ends up in the ocean. This realization seems only gradually to be reaching many people, as countless pieces of fishing gear from commercial fleets still disappear into the depths of our oceans every year. From shelf seas to deep-sea basins, Portuguese and Spanish researchers have surveyed European waters for plastic debris and published their findings in a study [Source 18]: it was present everywhere. The highest concentrations of plastic parts were found in deep-sea trenches, which are otherwise remote from direct human influence. Lost nets accounted for more than a third of the total waste volume. In the Baltic Sea alone, between 5,000 and 10,000 nets are lost overboard annually [Source 19].

Once lost, these nets act as drifting death traps. The duration for which they continue to capture marine organisms is not yet fully understood and depends on environmental factors, such as how quickly a net becomes so overgrown with algae, sponges, and crustaceans that it virtually merges with its surroundings. Estimates suggest it can take up to 27 months for a net to be rendered harmless by the colonization 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 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 cause immediate death, they severely restrict freedom of movement or prevent feeding. Because plastic does not biodegrade but is merely fragmented mechanically, individual fibres and microplastics form over time. Even then, the mortality does not cease: microplastics fill the stomachs of the smallest organisms in the food chain, and seabirds, including the Northern Gannets of Helgoland, unknowingly retrieve brightly coloured fibres from their journeys to use as nesting material. This decoration has already claimed the lives of numerous seabird chicks on the steep cliffs. Upon closer inspection, hundreds of carcasses hang like macabre figureheads from the red rocks.

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

Naturally, preventing the loss of these nets entirely would be far more effective.

Consequences of marine waste

Industrial and conventional agriculture results in massive quantities of phosphorus and nitrogen compounds entering the sea via rivers. This eutrophication stimulates algal blooms, leading to hypoxic "dead zones". A prominent example of this phenomenon is the Baltic Sea.

In the case of industrial wastewater, emissions, mining, and oil combustion, the threat lies not only in the quantity 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 not only been utilized as a testing ground for over 250 nuclear weapons tests, but also served from 1946 to 1993 as a colossal dumping ground for radioactive waste contained in metal drums. These drums are present in oceans worldwide, where they corrode and release ionizing radiation. Although this disposal method for solid radioactive waste was banned in 1993 under the London Convention (LC72), the direct discharge of liquid radioactive effluents remains permitted and continues to be practiced. Ionizing radiation, even in low doses, is associated with an elevated 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 petroleum consumption has nearly tripled [Source 25].

One of the most severe disasters in oil extraction occurred on April 20, 2010, when the British petroleum company BP's semi-submersible drilling rig "Deepwater Horizon" exploded in the Gulf of Mexico. Eleven individuals lost their lives, and oil discharged uncontrollably into the sea from the failed wellhead. Estimates suggest approximately 780 million litres were released. This volume contaminated a 75 km stretch of coastline and resulted in the mortality of thousands of birds, marine mammals, fish, and other marine organisms. Additionally, 40,000 people lost their livelihoods due to the catastrophe. Tanker accidents are no less devastating. The recovery period for nature following an oil spill varies according to the ecosystem and substrate characteristics, ranging from several months to 20 years [Sources 25-26].

Tons of toxic and explosive legacy munitions lie on our seabeds, posing a threat to humans, fauna, and the environment. Much of this material was simply dumped there after the war. Accidents could occur during the construction of offshore wind farms or the laying of submarine cables. As these bombs and munitions corrode further, 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 continuously rising noise levels in our oceans, all marine organisms are affected. Documented negative impacts include behavioural changes, altered migration routes, displacement from habitats, auditory damage, physical malformations, difficulties in conspecific communication (masked by anthropogenic noise), and mortality depending on the sound pressure level and stress response [Sources 28-29].