The oceans are in danger

 

 

By Science Columnist Ho-Gwan Ko

 

 

Oceans make up about 70% of the Earth's surface, and they contain more than 97% of the water on the planet. Accordingly, the oceans stabilize the Earth's climate. The ocean currents carry heat near the equator to cold, high-latitude regions. In addition, water temperature changes less than land temperature, keeping a daily temperature difference small. In places like deserts, the temperature difference between day and night can be as large as 50-60°C.

 

The sea also plays a significant role in curbing climate change. Water absorbs 1,000 times as much heat compared to the same volume of air. The sea absorbs the heat trapped in the Earth due to the greenhouse effect, suppressing global warming. However, it has limitations as well. Oceans are also affected by rising water temperatures, and many scientists point out that the damage from global warming can be much more severe in the ocean than on land.

 

When the sea temperature changes, the creatures living in the sea are naturally affected. We have discovered about 200,000 marine species so far, but scientists estimate that as much as 95% of the world's oceans are unexplored. Nobody knows how many more unknown marine species there are. According to scientific research, however, the number of marine species is declining. This can be attributed to indiscriminate overfishing as well as global warming.

 

When the sea temperature changes, the types of creatures living in it also change. In addition, global warming interferes with the mixing in the ocean where nutrients at a lower layer move upwards. In contrast, less oxygen is supplied in the deep sea.

 

Such results can be observed in the polar regions that are greatly affected by global warming. As warm water flows through the ocean currents, the types and numbers of plankton living in the polar regions are changing; the number of species living in relatively warm water is increasing. According to research, zooplankton that used to live in the Pacific Ocean was found in large quantities near the Arctic Ocean.

 

When a change is made to primary producers such as plankton, the entire food chain changes. For example, if the distribution of phytoplankton in the Antarctic Ocean changes, the krill that feed on it are affected, which leads to impact on large marine species from fish and penguins to whales that eat krill.

 

It’s not just the temperature, but the chemical properties of the sea water change as well. This is because seawater becomes acidic by absorbing more carbon dioxide from the atmosphere. Compared to pre-industrial times, the oceans today are 30% more acidic and will become more acidic in the future.

 

Ocean acidification adversely affects shellfish, crustaceans, and coral reefs that use calcium carbonate to build shells and skeletons. However, the more carbon dioxide in the seawater means the less carbonate ions needed to form calcium carbonate, which will eventually lead to a decrease in the species. But this is not it. Other creatures in the food chain will also be affected. In particular, if coral reefs, which provide shelters for numerous marine life, disappear, more animals will be put in danger.

 

Made famous by the animation film "Finding Nemo," the clownfish is another victim of ocean acidification. The clownfish and the sea anemone have a symbiotic relationship. The clownfish hides inside the sea anemone in case of an attack, then the sea anemone eats the predator. The impact of ocean acidification on the clownfish's ability to smell its way home to the sea anemone is threatening their life.

 

▲ Cute clownfish are also the victims of global warming!

 

When the underwater environment changes due to global warming, organisms respond in different ways, such as relocating habitats or changing food. However, each organism’s response will be different, and the ecosystem will eventually change in a way that is so complex that we cannot even predict. Changes in habitats, migration patterns, growth rates, and breeding rates will have a major impact on fisheries. You may have already heard a lot about fishermen catching different fish species than usual.

 

In May 2019, the scientific journal "Nature" published a study result that sea creatures are disappearing twice as fast as land creatures. We shouldn’t be only concerned about the fishery resources that make their way onto the dinner table. If we can’t stop global warming, the oceans will become empty in the future.