The pollution of our oceans is fast becoming one of the biggest threats to the future existence of mankind. As one of the world’s largest food sources and environmental stabilizers, if the ocean dies, the earth we know goes with it.
Most ocean pollution begins on land with unsustainable human activities. Some forms of contamination, such as the Great Pacific Garbage Patch in the Pacific Ocean, are well known and publicized.
Marine pollution comes in a range of visible and invisible forms which all need to be treated with equal urgency and care.
What are the most common marine pollutants & where do they come from?
Overall, despite global governmental and non-governmental efforts to combat marine pollution the situation continues to deteriorate. Nearly all pollution incepted into the marine environment is anthropogenically induced, and includes pollutants such as ocean litter, pesticides and fertilizers, or pollution in the forms of noise and light.
Specifically, marine pollution comprises of:
- Oil spills from rigs and tankers
Despite of what it seems thanks to the media coverage, oil spills are not the biggest source of oil pollution in the ocean. Oil spills only account for around 12 percent of all oil which enters our oceans. Over 35 percent comes from runoff and another 22 percent comes from tanker operations .
- Untreated sewage from industries and coastal area development
Another major threat to the marine environment is the physical demolition of marine habitats from dredging. Huge swathes of coastal land are being developed around the world for tourism and other activities that is creating unprecedented levels of untreated sewage being discharged into waters.
According to the United Nations Environment Program (2006) the issue of untreated discharged water is estimated to cost some USD 56 billion if it were to be tackled .
- Heavy siltation and eutrophication from farming
From an agricultural point of view, the use of pesticides and fertilizers has increased by 26-fold over the past 50 years which has created serious environmental consequences . Chemical application in farming pollutes regional water bodies with compounds that can kill non-target creatures and ecology.
Whilst fertilizers are not directly toxic per se, they can alter the marine environment’s nutrient system and create an intense growth of algae, which depletes oxygen necessary for other aquatic organisms.
- Invasive species from aquaculture and wildlife trafficking
Aquaculture industry often unwillingly introduces non-native species into marine ecosystems when equipment fails and farmed fish escape into wild waters. Under favorable conditions, these species then become invasive and contribute to the destruction of local ecosystem and its inhabitants. Besides predating on native species or feeding on aquatic flora, some species may even change aquatic conditions by, for example, digging up the substrate and increasing turbidity .
- Persistent Organic Pollutants (POP’s)
POP’s consist of groups of man-made chemicals such as organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) that accumulate in aquatic or terrestrial ecosystem when released into the environment. These substances can easily contaminate marine food chain and can be found in high concentrations even in remote arctic waters, slowly accumulating in tissues of aquatic animals .
A reasonable progress has been made on reducing POP’s as oil discharges and tanker accidents have been reduced by some 63 percent and 75 percent respectively from a mid-nineteen eighties baseline .
- Heavy metals and acidification from mining
Emissions of heavy metals and sedimentation from coastal development and mining activities, deforestation and mangrove clearing are generally rising. Heavy metals are naturally occurring elements in the environment, however, thanks to our activities the concentration in which they are released into the ocean exceeds their safe limits.
Scientists have also found out that heavy metals tend to stick to plastic debris and accumulate in extremely high concentration on plastic surface, further exacerbating the problem of heavy metal contamination of sea water.
- Radioactive substances from nuclear activity and other toxic waste products
For years the ocean has been a convenient dumping point for toxic chemical and radioactive waste.
For example, the British Nuclear Fuels plant at Sellafield had been depositing nuclear waste in the Irish Sea since 1950’s. Similar practices were recorded in numerous other locations such as dumping of radioactive reactors from Soviet submarines and weapons in the Arctic Ocean, or countless containers filled with nuclear waste along the coast of San Francisco .
Since the second half of 20th century, we have dumped in our oceans over 200,000 containers with radioactive waste, 14 nuclear reactors, 19 ships with nuclear waste and 6 nuclear submarines…and that’s only what we know of. The scale of possible contamination is probably much higher, since it has not been controlled in any way .
Although the London Dumping Convention of 1972 restricted what can be dumped at sea, there is still an unsustainable amount of toxins entering the marine environment.
- Litter from domestic waste and other activities
Single use plastic items like grocery plastic bags, straws, ear swabs, take away food containers, or cigarette butts, empty detergent bottles, discarded toys, medical waste and other items we use daily in our lives can all be found floating in the oceans, thousands of miles away from their original source.
Sadly, plastic makes the biggest part of marine litter. 80 percent of marine debris is plastic and according to the data from the Ocean Health Index, 8 million metric tons more enter the ocean each year.
- Destruction of coastal and marine habitats from overfishing
Overfishing is arguably the gravest of all detrimental marine activities, but from a pollution perspective it can cause contamination via the sheer amount of fuel, resources and waste created in its process.
Ghost fishing gear, that is gear left behind by fishermen, also represent a threat to marine ecosystem. A report issued jointly by the Food and Agriculture Organization and the UN Environment Program (UNEP), estimates that 640,000 tons of abandoned nets are spread across the world’s oceans, comprising up to a staggering 10 percent of oceanic litter.
How is ocean pollution affecting marine life?
Marine pollution has a vast range of effects, many of which are invisible to the untrained eye.
One of the biggest sources of pollution is called nonpoint source pollution. It occurs as a result of contaminated runoff after rainfall, and comes from septic tanks, vehicles, farms, and forest areas.
When this contaminated runoff water reaches the ocean, it harms delicate ecosystems by changing the water chemistry and causes unmeasurable damage of various scale to marine creatures . For example, nutrients from fertilizers and sewage can cause algal blooms which deplete the water of oxygen. This can cause mass fish kills and displace marine organisms.
Pathogens from sewage and untreated waste can return to the food chain through fish and shellfish and spread disease and illness when consumed.
Rising carbon dioxide concentrations affect coral reefs
One of the least obvious aquatic pollutants is carbon dioxide. Since the Industrial Revolution, mankind has been spewing huge quantities of CO2 and other greenhouse gases into the atmosphere.
From there, they dissolve in the ocean and cause huge problems including ocean acidification and rising water temperatures.
This is extremely harmful to corals, shellfish, and other organisms as it reduces their ability to form their solid shells or exoskeletons.
Radioactivity is killing
Radioactive waste has caused huge problems for marine life following the Fukushima nuclear power plant’s toxic waste leaks.
Since the disaster, millions of liters of radioactive water have leaked into the sea, where it is affecting marine organisms as far away as the west coast of North America. Although there is little concrete evidence, there are theories that this radiation has led to the mass deaths of a variety of animals in the western Pacific Ocean, including seabirds, dolphins, and seals.
Ship traffic affects marine wildlife
Noise pollution from large ships and machinery can disrupt many aquatic animals, particularly mammals.
Large cetaceans such as whales can become obviously distressed when there is too much background noise, as it can interfere with their communication and navigation systems.
The effects of marine pollution on human health
Human-induced marine pollution is not only harmful to the environment and marine life but to us as well. It can cause the build-up of toxic pollutants in sea food products, and even has the potential to make the ocean itself unsafe for us.
#1 Plastic in our food chain
The world’s oceans contain huge amounts of plastic, ranging in size from microscopic beads to large pieces of trash. Since plastic doesn’t biodegrade, it usually just keeps breaking up into smaller and smaller bits, eventually becoming microscopic sized pieces. As they are breaking up, plastics also release a number of deadly chemicals into the environment, some of which are easily absorbed by fish and shellfish.
We experience the negative effects of plastic pollution when we consume seafood.
Tiny plastic beads are ingested by fish and marine mammals – intentionally or not – and make their way up the food chain. These plastics can contain heavy metals such as lead, mercury, and cadmium. Many also contain Diethylhexyl phthalate, an extremely toxic carcinogen.
These and other toxins are often linked to cancer, birth defects, immune system problems, and childhood developmental issues .
#2 Industrial pollutants suffocating commercial fisheries
Many of our activities, especially around ports and other industrial areas, also have a direct impact on human health. Port activities often result in the release of heavy metals and toxins directly into the ocean, where they are absorbed by the sea-life.
Filter feeding animals such as oysters and mussels simply feed on whatever they filter from the water. Unfortunately, this also includes any toxins which are present. They can then store these toxins – often heavy metals – in quite high concentrations.
This can cause problems if commercial fishing or aquaculture operations are happening in the same area, as harvested seafood may be contaminated.
#3 Algal blooms
Agricultural runoff and sewage dumping can lead to major algal blooms, which in turn can have terrible consequences on anyone who comes into contact with them.
The high nutrient concentration in most agricultural runoff provides the perfect ingredients for algal blooms, which produce nasty toxins and lower the oxygen concentration of the water – particularly in protected areas such as bays and estuaries.
People who go swimming or perform other water-related activities in the area can come into contact with these toxins, which can make them very sick or cause long-term problems.
Seafood harvested from the affected area can also contain high concentrations of toxins and can cause food poisoning when consumed. For this reason, some fisheries close when major algal blooms occur.
Negative predictions for the future
A plethora of credible sources and international institutions predicts that the marine pollution issue will continue to worsen by 2030. Nitrogen from agricultural run-off is projected to increase at least 14 percent globally, with more than 600,000 tons being discharged annually from the major rivers of South-East Asia alone.
As coastal populations and industrial activities increase in the region from 77 people per square kilometer to 115 people per square kilometer in 2025, these numbers will become further exacerbated .
All of the above, together with the impacts of a warmer climate through climate change will also increase the salinity of our marine environment and raise water levels through the of melting sea ice which could hold its own set of pollution-related issues.