What are the modern day threats to the ocean and marine ecosystems?

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Nicola

The ocean covers 70% of the planet and is crucial to providing humans and nature many services. Scientists estimate that 5080% of the oxygen production on Earth comes from the ocean, it plays a fundamental role in moderating our climate, whilst also providing jobs, medicine and food. However, it is also the most vulnerable ecosystem in the world; with only 3.4% of it protected. For decades, the ocean and marine ecosystems have been facing disastrous threats which have resulted in problems such as a loss of biodiversity, an increase in ocean temperatures and pH imbalances. Researchers have identified many reasons as to why we have seen vast changes in the ocean including overfishing and eutrophication, but it has been made clear in particular by extinction rebellions and the media, that climate change is a large driving force. It must be considered what the largest threats are to our oceans today.

Coral reefs support 25% of all marine life in the ocean

Due to increased human activity and industrialisation the Earth is experiencing increasing levels of the greenhouse gas carbon dioxide, which contributes to climate change, this in turn creates problems for the ocean such as acidification and rising sea temperatures. Since 1980, the average temperature on earth has increased by one degree Celsius, raising temperatures in the ocean by as little as 0.1 degree can cause detrimental problems for marine life, such as for coral reefs which require specific temperatures to survive. Coral reefs support 25% of all marine life in the ocean, as the climate gets warmer, marine ecosystems become stressed due to the rapid changes to their environment. If factors such as temperature changes in the environment occur, the animal-algal mutualism existing between a coral polyp and a zooxanthellae in coral, fails under these new conditions. Zooxanthellae are expelled by the coral and causes the decline of coral reefs through coral bleaching. Climate change is the leading cause of coral bleaching, the WWF states that the entire reef ecosystem, which humans and wildlife depend on, will disappear by 2050. If we lose all of our coral reefs, huge amounts of marine life will be lost as well as crucial materials used in medicine, it will also have a detrimental effect on tourism, the fishing industry and would exacerbate natural hazards such as tsunamis which corals can protect us from.

Climate change also poses a threat to the ocean via acidification – the reduction in pH of the ocean over time has been linked to the uptake of carbon dioxide from the atmosphere. Oceans have absorbed 30% of all carbon dioxide and with increasing CO2 emissions (due to the continued burning of fossil fuels in industry), more is dissolving into the ocean increasing carbonic acid levels, making it increasingly uninhabitable. It is suggested that there will be an increase in ocean acidity of 170% by 2100, 10 times faster than any ocean acidifications for over 50 million years. Acidification has a direct impact on marine organisms especially those with calcareous skeletons or shells such as crustaceans and phytoplankton, as the concentration of carbonate ions in the seawater that they rely upon to make their shells, decreases. Shells also dissolve under these conditions and because acidification is happening at an unprecedented rate, scientists believe that species won’t be able to cope, leading to mass extinctions. In acidic waters, marine animals and plants also struggle to survive with depleting oxygen levels creating more competition between species for survival. Climate change is a huge threat to the ocean and marine ecosystems as they rely upon stable temperatures and conditions to thrive in. Anthropogenic climate change is hugely altering marine species in their abundance, diversity and distribution. As more carbon dioxide enters the air, oceans will struggle to adapt to fast changing environments posing a threat to marine species particularly crustaceans and coral reefs, of which we rely upon for our economy and safety.

Research has presented that overfishing is also a significant threat to the ocean and marine ecosystems. Such activity contributes to fish population depletion and habitat destruction. Catching fish is detrimental for the ocean when vessels catch fish faster than stocks can replenish, and it is done unsustainably. Frequent overfishing will disrupt populations as it happens faster than the fish’s ability to reproduce, this will affect food chains and create uncontrolled growth of other species such as plankton. There will be cases when the sea is contaminated or loses its clarity due to plankton filling up,

this causes problems for fishermen as well as the marine biodiversity. Systemic overfishing is made worse by illegal catches and trade. In fact, some of the worst ocean impacts are caused by pervasive illegal fishing, which is estimated at more than 30% of catch for high-value species. The number of overfished stocks globally has tripled in half a century as the demand for fish supply and food has risen; commercial fish populations of cod, hake and haddock have dropped as much as 95%, provoking calls for urgent measures. Overfishing also links with bycatches where nontargeted species are incidentally captured, this happens commonly with dolphins and turtles. Today, onethird of the world’s assessed fisheries are currently pushed beyond their biological limits. With advanced technology and unselective modern fishing gear, fishermen can now catch larger numbers of fish at once with thousands of miles of nets set out in the world’s oceans each day. Extremely strong and often undetectable netting regularly catches marine animals which are then discarded overboard dead or dying. It is estimated that over 300,000 small whales, dolphins, and porpoises die from entanglement in fishing nets each year, making this the single largest cause of mortality for small cetaceans. Species such as the Maui’s dolphin from New Zealand faces extinction if the threat of unselective fishing gear is not eliminated.

A further threat to the ocean is pollution of the waters due to eutrophication.

Algae in waters photosynthesize and provide oxygen for aquatic animals, but as more fertilizers (mainly from industrial agriculture), detergents and sewage runs off into rivers and lakes, nitrates and phosphates overly enrich the waters causing excessive growth of algae. Sea food and tourism industries have had to spend $82 million a year on reducing dead zones and make waters safe to swim in due to eutrophication. The Gulf of Mexico is just one example where nutrient rich waste from 31 states all flow into the same basin, creating an uninhabitable environment for plants and animals with less than 2 milligrams of oxygen per liter in the waters. Algal blooms block sunlight which causes aquatic plants to die which in turn creates further oxygen depletion in marine ecosystems. Due to these issues, people in industry are working on reducing eutrophication by creating buffer zones of trees and shrubs in farms and areas of runoff such as in Mexico, to absorb most of it before reaching the ocean, but this won’t be enough if we want to solve its long term problems of pollution and decreasing levels of oxygen for organisms.

Further pollution comes in the form of plastic, the excessive use of plastic is a concerning issue as much of this waste ends up in the ocean and by the 2050 there is predicted to be more plastic than fish in the sea. Plastic bottles for example, can take over 450 years to break down and if they haven’t been consumed by marine animals before then, dangerous chemicals are released into the waters during decomposition along with the formation of microplastics which do not disappear. Evidence has found plastic in the fish that we consume, showing the scale and detrimental effects of this issue, its terrestrial impacts will affect our fishing industries and economy in the future due to poor quality of food. In 2018, Seattle became the largest U.S. city to ban plastic straws and large companies such as Starbucks and McDonalds began to do the same. This gives hope for a plastic free future where marine ecosystems are less in danger but it may be a process that isn’t fast enough. Ships travelling from coast to coast also introduce threats to the ocean with

Sea food and tourism industries have had to spend $82 million a year on reducing dead zones

oil spills. In July, MV Wakashio, a bulk carrier carrying 4,000 tons of oil, crashed into fragile coral reefs a few kilometers from Mahebourg, SE Mauritius. Under two weeks later, oil started turning the sea and shores black. Oil spills reduce the availability of oxygen and cause many issues such as hypothermia to mammals with fur, such as otters and seals or breathing problems for fish resulting in instant death; lower fish availability will significantly affect the economy. Not only do issues like this occur in the ocean, but it also affects birds that search for food in these waters or normally migrate to these regions. Water pollution has been a large threat to the ocean, it takes dedication to reduce such threats and changes in our behavior and attitudes. We are attempting to make a difference in how we use plastics and fertilizers, but a bigger issue is the use of fossil fuels and the rate at which they are currently being burned, leading to irreversible changes to the ocean.

Overall, it can be concluded that the ocean and marine ecosystems are facing unprecedented changes and threats, which are slowly creating problems for humans too, mainly concerning industries and economic decline. Losses in biodiversity imply a loss of genes and molecules that are potentially valuable for medical research and industry. Oceans must be protected from human induced problems, especially those related to climate change. Industries are becoming more aware and educated about overfishing and trawling and so are making changes to the way they work to be more environmentally friendly and sustainable. Although it is difficult to control illegal fishing, this issue is less of a threat to the whole ocean. As well as this, it is more reversible and manageable than the mass water pollution associated with the overuse of plastics and industry. Plastics and chemicals stay in the ocean long term, whilst there is a greater hope that we can repopulate fish species and form new fishing methods. Climate change is considerably the largest and fastest modern-day issue, which must be addressed in order to reduce the extreme impacts to the ocean and marine ecosystems. Scientists show that if we use environmentally friendly alternatives to fossil fuels and reduce CO2 emissions, coral reefs will survive in the future and a quarter of marine life will still have a habitat to live in.

References: DOF (2018). 17 Biggest Threats to Ocean Ecosystems.Available: https://deepoceanfacts.com/threats-to-ocean-ecosystems#:~:text=Global%20 warming%20is%20a%20major%20threat%20to%20the,of%20pressure%20and%20stress%20from%20the%20rapid%20changes .. Last accessed 15th Nov 2020. WWF (2019). CORAL REEFS AND CLIMATE CHANGE: FROM CRADLE TO AN EARLY GRAVE.Available: https://www.wwf.org.uk/coral-reefs-andclimate-change . Last accessed 15th Nov 2020. Deep Ocean Facts (2020). 25 effects of overfishing.Available: https://deepoceanfacts.com/effects-of-overfishing#:~:text=%2025%20Effects%20 of%20Overfishing%20%E2%80%93%20Risk%20%E2%80%93,for%20human%E2%80%99s%20health.%20It%20has%20omega%2C...%20 More%20 . Last accessed 16th Nov 2020. 15th Nov 2020. .