Our planet relies on the oceans as climate regulators. At the same time, the effects of our emissions are most evident in the oceans. Today, eutrophication, climate change, ocean acidification, and invasive species are some of the challenges the oceans face. The Ocean – A key player in climate
The oceans are already significantly impacted by human activity, making them sensitive to further influence from climate change. Habitats of species may disappear, shift, or shrink, while others gain access to new distribution areas. This can lead to a reduction in biodiversity, exacerbating the oceans’ resilience against, for example, climate change.
According to the International Panel on Climate Change (IPCC), over 90 percent of excess heat and between 20 and 30 percent of carbon dioxide emissions have been absorbed by the oceans. Carbon dioxide is absorbed by the oceans as the gas dissolves in water, and phytoplankton in surface waters take it up and bind it in organic material through photosynthesis. Phytoplankton are then consumed by zooplankton, which, along with other organisms, fall towards the ocean floor as marine snow when they die. This process allows large amounts of carbon from the upper layers of the ocean to reach deeper layers which is crucial for the organisms there. The transport of carbon to the bottom also ensures that it remains in the oceans much longer than if it were to stay in the surface layer, potentially leaking carbon dioxide back into the atmosphere.
One effect of increased emissions of greenhouse gases is ocean warming. When the oceans become warmer, the entire ecosystem is affected. Fish size may change, algal blooms and dead zones increase, and many species such as eelgrass, harbor seals, and mussels struggle to survive. Furthermore, as water becomes warmer, it becomes more challenging for the oceans to absorb carbon dioxide, potentially worsening climate change further.
The warming of the oceans is now the fastest in at least 11,000 years. Although it can be slowed down with powerful measures, the stored heat energy contributed so far will continue to warm our planet for hundreds or even thousands of years.
The oceans play a large role in how we experience the climate on our planet. Thanks to the Gulf Stream, Nordic countries for instance have a relatively mild climate in relation to their northern positions. Warming of the seawater leads to significant changes in ocean circulation and rising sea levels as the ice in the ocean’s melts. The decrease in ice is more pronounced in the northern hemisphere than in Antarctica, and research indicates that the ice will continue to melt for at least 100 years, regardless of the measures taken. However, the effects worsen with the more greenhouse gases we emit. Many scientists are concerned about how the Earth will be affected when the Arctic ice disappears, as it affects the climate by reflecting solar radiation.
Climate change will affect the salinity of the oceans. In areas near the equator, evaporation will increase, leading to an increase in salinity. In areas closer to the poles, such as the Swedish seas, salinity will decrease as precipitation and the influx of freshwater increase and polar ice melts.
Changes in salinity and temperature can, among other things, lead to increased oxygen deficiency. This is because the stratification of seawater in depth becomes clearer, preventing mixing and transport of oxygen-rich water to the bottom. Salinity and temperature also largely control the geographic distribution of species, meaning that climate change can have significant consequences for biodiversity.
The absorption of carbon dioxide by the oceans has almost doubled since the 1980s, but it has come at a cost. When carbon dioxide is mixed into the water column, the chemistry of the ocean changes. A higher concentration of carbon dioxide in the ocean increases acidity, a phenomenon called ocean acidification, sometimes referred to as the “evil twin of warming.” Like the effects of climate change, ocean acidification can lead to the extinction of species or shifts in ecosystems. Studies show that key species such as brittle stars in Gullmarsfjorden would not survive the acidification expected within a few decades. And since many species depend on them, it can have significant consequences for the entire ecosystem.
Ocean acidification affects various biological processes such as photosynthesis and calcification. Many marine organisms are affected by the fact that ocean acidification makes calcium less accessible, as they form shells and skeletons from calcium. Corals are affected by both calcium deficiency and increasing temperature. Coral reefs are one of the ecosystems with the highest biodiversity globally but are also most affected by climate change, leading to coral bleaching. Even the coral Lophelia in Kosterhavet National Park is affected by increased temperature and acidity.
Today, several marine areas, such as the Black Sea and the Baltic Sea, are affected by eutrophication. This is due to increased nutrient input, leading to the proliferation of fast-growing phytoplankton, cyanobacteria, and filamentous algae. This makes it difficult for other species to survive as much sunlight is blocked. When the algae sink to the bottom, bacteria use up the oxygen to break down the organic material. This has resulted in large dead zones in, for example, the Baltic Sea, where only bacteria and a few other microorganisms can survive in the oxygen-depleted environment. Eutrophication leads to overgrown bays, deteriorated water quality, and reduced biodiversity.
While some nutrient inputs occur naturally, human activities contribute significantly by adding extra nutrients in the form of nitrogen and phosphorus. Agriculture, sewage, industries, forestry, road traffic, and shipping all contribute to eutrophication. Because eutrophication in the Baltic Sea has been ongoing for so long, there are old sins in the form of nutrients bound in sediment. Internal loading is a process where these nutrients are released, mainly when there is limited oxygen at the bottom. Eutrophication thus creates a negative spiral where the system eventually feeds itself.
Although the eutrophication status is still poor in most parts of the Baltic Sea, improvements can be seen in the Gulf of Finland, Kattegat, and the Belts. According to the Helsinki Convention, HELCOM, nitrogen inputs have decreased by 19 percent, and phosphorus by 24 percent since the mid-1990s. To further reduce the impact of eutrophication, the main sources, namely agriculture and wastewater, should be controlled.
Many environmental toxins have decreased significantly since the 1970s. However, society’s extensive use of chemicals needs further reduction. History speaks clearly: actions make a difference.
Almost all toxic substances released into nature are considered environmental toxins. Some of these can harm animal and plant life even at low levels if they persist for an extended period. Environmental toxins often break down slowly, meaning their effects can be both long-lasting and spread over large areas. Some common environmental toxins include mercury, lead, cadmium, tributyltin (TBT), DDT, PCB, and dioxins.
Most organic environmental toxins are fat-soluble and therefore accumulate in the fat tissue of various organisms. Toxins accumulate to a greater extent the higher up the food chain you go. Therefore, top predators, often suffer more from environmental toxins than prey animals. When humans eat fish that have stored environmental toxins, they ingest these toxins. This has led to specific dietary recommendations for pregnant women, children, and young people when it comes to fatty fish.
White-tailed eagles and seals were heavily affected by environmental toxins during the 1960s and 70s because they are long-lived animals high up in the food chain. The white-tailed eagle was close to extinction because the chicks did not survive. Seals in the Baltic Sea struggled to reproduce, and in combination with hunting, environmental toxins led to only a few thousand seals remaining. After measures were taken to reduce the levels of environmental toxins, white-tailed eagles and seals in Sweden increased.
But despite the prohibition of PCB and many measures aiming at reducing the spread of environmental toxins, the levels are still relatively high. Some dioxins are considered some of the most dangerous environmental toxins as they can affect the development of our brain, immune system, nervous system, and the ability to have children. This is due to their long-lasting nature and the existence of emission sources that Baltic Sea countries have not yet addressed. Additionally, humans constantly introduce new chemicals that risk reaching the oceans.
A common pollution in the oceans today is plastic. In the oceans, more than around 150 million tons of plastic float, increasing by 5 to 13 million tons each year. Estimates show that 80–85 percent of marine litter in the EU consists of plastic. Of this, 50 percent are single-use products, and 27 percent are fishing-related items. Lost fishing gear, such as nylon nets, often float around as death traps for animals, known as ghost nets. Whales, seals, seabirds, and other animals can get entangled in these and die.
To try to reduce the problems of plastic waste in the oceans, the EU introduced a directive against single-use plastics in 2021, prohibiting the sale of plastic straws, among other items. Since it takes several hundred years for plastic to break down in the ocean, it instead slowly disintegrates into smaller parts, eventually becoming microplastics. Microplastics are also flushed into the oceans from wastewater treatment plants, often originating from fabrics made of synthetic materials and additives in hygiene products and cosmetics. About 10–30 percent of plastic particles elude capture by wastewater treatment plants and end up in the oceans. If animals ingest microplastics, they can be harmed or poisoned. Additionally, when they consume plastic, a false sense of being full occurs, leading to malnutrition. In water, plastic particles act as magnets for bacteria and environmental toxins, which animals ingest.
Although no significant risks for the environment and health have been found with current concentrations of plastics, knowledge gaps are significant. This currently prevents any conclusive statements about the risks of microplastics.
TEXT: Lina Mattsson
Everything we do in the high sea, risks causing damage that cannot be repaired. That's what a group of leading scientists say in a recent article published in the journal Nature. They say it's damaging biodiversity, affecting the climate, and creating huge inequalities in how resources are shared. It is time, they write, that we decide to save the ocean.
A huge area of the ocean – four times the size of Europe – was hit last year by an unprecedented marine heatwave.
Plastic, overfishing, global warming and fighting over resources. Despite several urgent problems, oceans and marine resources are the most underfunded of the UN's sustainability goals. At the ocean conference in Nice, countries will now try to agree and find funding to protect and preserve the world's oceans.
If the Gulf Stream changes direction or stops completely, it will have devastating consequences for us in northern Europe. Perhaps these areas will become uninhabitable. But will this really happen? Danish researcher Jonas Teilmann and his team are attaching tracking devices to whales off Greenland to find out what is happening in the ocean right now.
High levels of ammonia from penguin poop may help reduce the local effects of climate change in Antarctica, according to a new study. - It was surprising to me, researcher Matthew Boyer told TT.
More than 3,500 animal species are threatened by climate change, according to a new analysis. - We are at the beginning of an existential crisis for the Earth's wildlife, says Professor William Ripple, one of the researchers behind the study.
Tropical islands are popular travel destinations among the Nordic citizens and especially the scuba divers. Nevertheless, what at first sight looks like a paradise, often at a closer look appears as a location with several environmental challenges. This has to do with the fact that, due to their size, small tropical islands have only limited natural resources and a low carrying capacity.
At 99 years old, Sir David Attenborough delivers the most important film of his career. The hope is that ‘Ocean’ will play a decisive role in saving biodiversity and protecting the planet from climate change.
In the heart of Raja Ampat is the small island village of Arborek, home to the NGO Barefoot Conservation. The team at Barefoot Conservation has been monitoring the reefs around the island, collecting samples and tracking the spread of cyanobacteria. Their research is critical to understanding how to protect these reefs and the communities that depend on them for food, income, and tourism.
The EU law to reduce the number of corks discarded in nature was introduced last year. But according to a new report, the number of plastic corks polluting beaches along the West Coast of Sweden increased for the first time in years.
The UN's maritime organisation, IMO, has agreed on a new treaty with binding requirements to bring shipping's climate emissions down to net zero by 2050.
The impact of humans on plants and animals is much more extensive than previously thought. Vertebrates in particular are showing a significant loss of diversity, according to an international study.
Spring is coming, even to the North Pole. But winter is summarised by alarm bells - never before has ice cover peaked at such a low level as this season, according to the Danish weather agency DMI.
The swedish government is proposing to make the Nämdö Archipelago a new national park - the first marine national park in the Baltic Sea.
Sea ice continues to shrink. In early February, their extent in the polar regions reached a new record low and remained below the previous record set in February 2023 for the rest of the month, reports the EU's Copernicus climate service.
The world's largest iceberg appears to have run aground - some seven miles from a potentially fatal collision.
Sunscreen protects our skin from the sun's ultraviolet rays that can lead to skin cancer. But what protects us can also pose a significant risk of bleaching corals and reducing fish fertility. That's according to a new report compiled by researchers at the University of Plymouth.
Sea ice at the poles, which helps cool the Earth, is at its lowest levels recorded this time of year, according to new satellite measurements, reports the BBC.
With a warmer climate, the sea ice is melting and more species are moving to northern latitudes. For killer whales, the melting sea ice provides new roaming opportunities further north into the Arctic Ocean.
In Raja Ampat, Indonesia, marine life has made a remarkable recovery, thanks to the establishment of large marine protected areas. However, not all species have bounced back. It’s estimated that only 20 adult Indo-Pacific leopard sharks remain, severely impacted by overfishing. Can this species be saved? And why is that important?
The world's largest iceberg is drifting towards an island where it risks disturbing penguin chicks and seals, a scientist warns.
Methane from the exploded Nord Stream pipeline has spread to large parts of the southern Baltic Sea. Over 20 marine protected areas are affected. This is shown by a new study. – How long the methane stayed in the sea and how far it was able to spread was quite striking to me, says Bastien Queste, associate professor in oceanography and co-author of the study.
Methane from the exploded Nord Stream pipeline has spread to large parts of the southern Baltic Sea. Over 20 marine protected areas are affected. This is according to a new study. - ‘How long the methane stayed in the sea and how far it could spread was quite striking to me,’ says Bastien Queste, associate professor of oceanography and co-author of the study.
When world-renowned ecologist and coral reef researcher Mark Erdman first arrived in Raja Ampat, Indonesia, in the early 2000s, both dynamite and shark fin fishing were still going on. He describes it as if all the major valuable fish species had been fished out. But today, when we meet him in Raja Ampat, we find a completely different reef, full of sharks and small fish.
