The world’s oceans are a fundamental the natural system on Earth. This is hardly surprising when you consider that up to 71% of the planet’s surface is covered by oceans. And these oceans are but one example of marine ecosystems. These diverse, vibrant environments support a bewildering amount of life.
However, these areas are sadly under threat from a variety of issues, many of which have been exacerbated by human activity. Climate change, plastic and chemical pollution, and industrial processes all have detrimental effects on marine ecosystems.
But what are marine ecosystems? Why are they facing these threats? And what can we do to help protect them and make them more resilient to these external pressures?
What are marine ecosystems?
Marine ecosystems can broadly be defined as ecosystems that occur in saltwater, such as the seas and oceans. The water of these environments has a high level of dissolved salt, which sets them apart from freshwater ecosystems.
There are three well-known types of marine ecosystems; coral reefs, the open ocean, and the deep ocean. Tidal estuaries, salt marshes, and mangrove forests are other forms of marine ecosystem that can be found in areas across the globe.
Coral reefs are delicate marine ecosystems that support a rich variety of marine life. Reefs are made from calcium carbonate layers that are produced by coral polyps, and over time form impressive structures in the water. Coral reefs are extremely important as a marine ecosystem, supporting as much as a quarter of all marine life. Animals that live around coral reefs include fish, turtles, molluscs, dolphins, and sharks.
The next two marine ecosystems are the open ocean and the deep ocean. These two types of oceans can be further defined by a series of zones that indicate how much sunlight reaches various levels of the water.
The open ocean mainly consists of the euphotic zone, which covers the first 200 metres of water below the surface. These areas have lots of sunlight, good oxygen levels, and warm waters. Marine plants or other organisms that rely on photosynthesis are found here, as well as the majority of marine life like fish, dolphins, seals, sharks, and whales.
As we descend deeper, the open ocean gives way to the deep ocean. Here, due to the dysphotic and aphotic zones the temperature drops, and less and less sun reaches these waters. The dysphotic zone reaches 1000 metres below the surface, with photosynthesis still possible.
The deepest level, the aphotic zone, has no sunlight at all. Animals such as anglerfish and squid roam the darkness. Deeper still, close to the Earth’s crust, strange creatures like giant tube worms live around hydrothermal vents in searing conditions. It is speculated by some scientists that bacterial life first began at these levels, billions of years ago.
Earth’s oceans: The current state
Right now, our oceans are facing unprecedented challenges such as climate change, pollution, overexploitation, and the destruction of marine habitats. The majority of these issues have been caused or exacerbated by human actions. Climate change, chemical pollution, plastic refuse, and habitat destruction are all major issues facing marine ecosystems. These issues have already begun to take effect in oceans around the world, and will also rapidly begin to pose dangers to us.
Climate change has immense effects on delicate marine ecosystems. Many habitats and species that live in the oceans are extremely sensitive to changes in water temperature and pH levels. Due to climate change, the oceans are gradually getting hotter and more acidic. As this causes problems for marine life, it may also cause issues for our food chain, affecting fish stocks. This may be felt especially hard in island communities that rely on fishing for both sustenance and employment.
Chemical pollution is becoming more of a problem for the oceans. Many chemicals such as fertilisers or ingredients used in hygiene products are entering the oceans, having detrimental effects on marine life and also infecting water supplies. This may affect us as this polluted water cycles back into our own water systems.
Plastic refuse is one of the more visible issues for marine ecosystems. Virtually any beach in the world is littered with discarded bottles, bags, and other plastic products. Plastic does not biodegrade, it only breaks down gradually into smaller and smaller pieces. These plastic fragments leach chemicals into the oceans as well as entering the marine food chain, which may eventually cause us to be ingesting plastic as well.
Habitat destruction is affecting many marine ecosystems. Human processes such as oil drilling, deep sea mining, and aggressive fishing methods can destroy marine habitats that are important for many forms of life in the ocean. This has knock-on effects on the food chain as well as our own fishing stocks.
The overall outlook for the health of our oceans looks disconcerting at present. It is estimated that by 2050, there could be more plastic in the ocean than fish. Some scientists believe that we can use the deep ocean to maintain an up-to-date outlook on the health of global oceans. As much as half of the oceans on Earth show signs of being affected by climate change. Teams researched how different areas are being affected, finding that Southern oceans were being altered more quickly than those in the Northern hemisphere.
The impact on coral reefs
As mentioned earlier, coral reefs are rich marine ecosystems in the open ocean, mainly in tropical waters. They are formed very slowly by layers of calcium carbonate that are produced by coral polyps. Over time, immense coral structures are formed. Despite making up less than 1% of the Earth’s oceans, coral reefs may support as much as ¼ of all recorded marine life.
However, the impact of issues such as climate change and human activity paints a bleak picture for coral reefs. Around 25% of coral reefs are damaged beyond repair. The rising temperatures and acidity of the oceans thanks to climate change disrupts the delicate balance of these incredible ecosystems. Coral becomes bleached by heat and acid, which causes it to die. This then makes it useless as a habitat for other marine life.
Aggressive fishing methods and marine industrial processes can seriously damage coral reefs. We have already lost up to 19% of the world’s coral reefs. Some estimates predict that by 2050, all of the world’s coral reefs could be gone.
Some man-made products are particularly harmful to delicate coral reefs. Chief among these are personal care products such as shampoos, sunscreen, lotions and shower gels. This is because these products contain certain chemicals, like oxybenzone, that are damaging to sensitive reefs.
By reducing our use of chemicals harmful to coral reefs, we can help stave off the extinction of these fascinating organisms. Some sunscreen companies are pioneering products that are “reef-safe”. These products substitute chemical UVA/UVB blockers for natural ingredients that are more friendly to coral reefs, such as titanium dioxide and zinc oxide. These products should have labels on their packaging which tells you if they are reef-safe.
What’s harming marine ecosystems?
Marine ecosystems are understandably, extremely complex systems with many interactions, dependencies and connections. As you might have guessed already, with this level of complexity comes a whole lot of places where external pressures are felt by various parts of the system. But what are some of the main perpetrators when it comes to these external forces and how exactly are they affecting the resilience of marine ecosystems as a whole?
As global temperatures rise, so too does the temperature of the oceans. For scores of marine creatures that live in very delicate ecosystems, especially in tropical areas, this can cause catastrophic effects. Nowhere is this more evident than in coral reefs. Climate change is being accelerated by our continued reliance on fossil fuels, which are pumping greenhouse gases into the atmosphere and causing temperatures to increase.
Changing temperatures can also alter important migration patterns for several marine creatures. This can have knock-on effects and can end up disrupting food chains and breeding cycles. The higher levels of carbon dioxide and other pollutants in the atmosphere due to global warming can also cause imbalances in the important pH levels of ocean waters, which are sensitive to such changes. As global warming continues, the ocean is becoming more acidic, which is harmful to sensitive marine ecosystems such as coral reefs.
One of the more pressing issues facing marine ecosystems is the rapid torrent of plastic flooding into the oceans. Up to 8 million tonnes of plastic enters our oceans every year. Refuse is being collected in floating islands such as the Great Pacific Garbage Patch, which stretches for up to 1.6 million square kilometres. Products such as plastic bags are frequently mistaken for food by marine animals.
However, their stomachs cannot break down plastic, causing them to die. Turtles and dolphins, among other creatures, have been found to have died in this way. Plastic continues to break down into smaller and smaller particles, which drift down deeper into the oceans. Microscopic animals like plankton, which make up the bottom of the marine food chain, ingest these microplastics, causing knock-on effects throughout the rest of the chain.
Products such as skin care scrubs can contain tiny balls of plastic called microbeads. These are flushed into our water systems, which eventually reach the oceans. There, these microbeads and other microplastics clump together, leaching chemicals as well as being ingested by marine life. Other examples of products that cause plastic pollution are plastic bottles, plastic bags, microfibres from synthetic clothing collected by our washing machines, and artificial grass fibres that are washed into the oceans due to water runoff.
Aggressive fishing methods
Overfishing can severely reduce the stocks of fish in our oceans and damage marine ecosystems. And it isn’t just humans that depend on fish for sustenance. Marine animals such as sharks, dolphins, whales, seals, and crustaceans all rely on fish as a vital part of their food chains. Since the 1960s, 90% of the top ocean predators have been lost. Aggressive overfishing can deteriorate fish populations, making them unable to recover and quickly reproduce to satisfy demand.
Some fishing methods are also destructive to marine habitats, such as coral reefs. Trawling is one such destructive method. Huge industrial trawlers use heavy machinery to cut swathes through the water, gathering up vast quantities of fish. Unfortunately, this machinery can also devastate coral reefs and other marine ecosystems due to its unwieldy nature. Cyanide fishing and the use of explosives to stun or kill large amounts of fish also has incredibly harmful effects on habitats.
To feed our continued need for fossil fuels, and even rare metals that are required for the construction of batteries for electric cars, humans have turned to the oceans. Oil rigs and drills dig deep into the underwater crust to dredge up oil, which causes devastation to marine habitats. When things go wrong, the consequences for marine ecosystems can be severe, such as the notorious Deep Horizon oil spill in 2010.
Deep sea mining, for valuable metals such as cobalt and nickel, is a rapidly growing practice that can severely damage marine ecosystems. These metals are often needed to produce batteries for both our electronic devices such as smartphones and computers, and for electric and hybrid vehicles.
Another human product and process that can be damaging to marine ecosystems are chemical pollutants. These can either come in the form of fertilisers, or on harmful chemicals used in rinse off personal hygiene products.
Chemical fertilisers are often sprayed on our crops and agricultural lands in order to increase their yield, while chemical pesticides are used to protect these crops from being ravaged by insects and other pests. Unfortunately, these chemicals eventually seep into the soil, and when rain comes, these chemical deposits are washed into rivers and streams due to surface run-off. Eventually, these pollutants enter the oceans, and can severely harm marine life as well as coral reefs.
Harmful chemicals used in personal hygiene products, such as parabens, have a similar effect. Some of the biggest culprits are body washes and similar products, which are rinsed off and travel through the sewage system and into the ocean. Sunscreens are also another product usually rife with chemicals harmful to marine ecosystems. Coral reefs can be irrevocably damaged by such chemicals, which can bleach the corals or render them sterile.
What’s being done to protect marine ecosystems?
In response to the dire straits facing our marine ecosystems, a number of responses to various issues detailed above are being put into practice. These methods can gradually turn back the tide and help protect marine ecosystems in the future. The Great Barrier Reef in Australia, one of the most famous coral reefs in the world, is seeing a range of local industries take steps to protect it.
One of the main ways to try and mitigate the damage caused by overfishing and its methods are the introduction of sustainable fishing practices as well as the reduction of fishing subsidies. These subsidies allow fishing fleets to work the sea harder as they will be rewarded by their governments. By reducing these subsidies and introducing sustainable fishing practices, overfishing can be reduced and prevented. Various non-profit and government sponsored sustainable fishing programs have been established around the world,
Creating marine protection areas
In the same way that National Parks protect vulnerable areas on land, so too can initiatives such as marine parks safeguard marine ecosystems at risk from damage. Establishing marine protection areas can protect threatened species such as turtles and dolphins, whilst also protecting fragile marine ecosystems such as coral reefs. In the Americas, over 4 million square miles of marine habitat have been protected.
Regulating marine tourism
Tourism can be a hidden cause of damage to marine ecosystems. Boating trips, diving areas and other tourist activities can be harmful. But regulating marine tourism, in concert with establishing and advocating protected marine parks, can turn tourism into a useful tool. Governments or companies that support sustainable marine tourism could be rewarded. And by protecting marine ecosystems that are such a draw for tourists, these incredible environments can sustainably generate income for decades to come.
What can we do as individuals?
It isn’t just large-scale changes that are needed to help protect marine ecosystems. We can each contribute on the individual level as well. One of the main ways we can all act to help is to reduce our consumption of plastics, especially single use items, which have already found their way into the deepest levels of our oceans.
Focusing on reusing and recycling plastic items, or replacing single use plastics with reusable alternatives like aluminium water bottles, can help reduce the amount of plastic that ends up in our oceans.
We can also be more conscious about the kinds of products we use and who we buy them from. For example, buying hygiene products such as sunscreen that are certified as Reef-safe is a good place to start.
While some of the damage done to marine ecosystems cannot be undone, we can still all work together to protect our oceans more strongly in the future. By taking actions as individuals, as well as wider changes in industry and society, we can tackle the issues facing marine ecosystems and avoid causing more damage in the future.
We have already seen evidence of previously damaged coral reefs gradually returning to life. If we all work together, there’s no reason why this can’t become the norm going forwards.