Ocean acidification is currently one of the serious issues that are widely discussed in the scientific community. But in the general public, people don’t have much knowledge about it. So what is ocean acidification? Ocean acidification refers to the tendency of the pH value of the Earth’s oceans to gradually decrease after ingesting carbon dioxide in the atmosphere . Since the 21st century, with the rapid development of industry and technology, people are emitting a large amount of carbon dioxide into the atmosphere. Among the total of carbon dioxide that humans have been emitting, there are about 30% to 40% of carbon dioxide will be dissolved in oceans, rivers, or other kinds of water bodies. The parts of carbon dioxide will mix with water and generate chemical reactions, forming carbonic acid, and ionizing hydrogen ions. These chemical reactions have led to a reduction in alkalinity and a sharp rise in acidity in the ocean. Ocean acidification with other biogeochemical changes will severely damage the ecosystems and its functions and affect many marine species. Among tens of thousands of different types of marine life in the oceans, plankton is arguably the most basic and important species. Plankton as the lowest layer of the marine food chain plays a huge role in both the effects of other marine life and many important chemical elements in the oceans. So is there any relationship between ocean acidification and plankton? Will they affect each other? I believe that there must be some kind of chemical and biological way of interaction between the two of them. So in this final paper, I would like to find some credible sources and do further research into the story behind plankton and ocean acidification.
During my research, the first thing I found is that ocean acidification will cause plankton to grow slowly. In the article “Persistent carry‐over effects of planktonic exposure to ocean acidification in the Olympia oyster”, the researchers had been observing Olympia oyster growth rate by reducing pH in seawater. Comparing with the oyster that grew in normal pH rate seawater, the growth rate of oysters in settling pH water (with pH rate 7.8&7.9) is significantly slower. The larval shell growth rate of larvae reared at pH 7.8 was reduced by 15%, and the shell area was reduced by 7% during settling. The effect was even more pronounced a week after settling, with larvae fed as larvae growing 41% slower in their shells at reduced pH rate. The effect will remain on the oysters for a long time. Even though the oysters may change a new environment later, it may still have a 1-1.5 month effect on them. In addition, under ocean acidification, the plankton imaging system revealed significant temporal changes in the size and structure of the copepod community during plankton blooms. The observed shift to smaller individuals has resulted in a 25% overall decline in co-foot biomass, although the number has increased. This experiment fully illustrates that the acidification of the oceans slows the growth of plankton.
Ocean acidification not only can slow the growth of plankton, but it is also more likely to cause their death. As I said earlier that plankton plays a huge role in the marine food web. Among these planktons, there are two main types of zooplankton (tiny floating fluids) that makeup shells made of calcium carbonate: Foraminifera and Pteropods. Both of them are important in the carbon cycle because the calcium carbonate shells they carry can slow down the temperature rise caused by the greenhouse effect and remove carbon dioxide. But the scientific data shows by the end of this century, both of them in the tropics will become extinct. The main reason for their possible extinction is because they cannot handle well with higher acidity. The acidity will corrode their shells. Once they become extinct, the Earth’s greenhouse effect will become more and more serious.
Speaking of plankton affecting the greenhouse effect, I have to introduce that “how can tiny plankton greatly contribute to global warming”. As the ocean becomes more acidic, plankton may produce fewer compounds, which are the keys to cloud formation. Clouds help keep the planet cool. Scientists have found that plankton produces a compound called Dimethyl Propionate, the name is abbreviated as DMSP. This substance can breaks down into various forms, and once they enter the atmosphere, they are easily transformed into tiny aerosol particles. These aerosols are the seeds of thick, low-level clouds on the ocean, which can effectively reflect sunlight back into space. Bacteria in the ocean can break down DMSP into DMS, which is dimethyl sulfide. It is the main raw material for aerosols that stimulate cloud formation. However, scientists have found plankton’s DMSP production will decrease if ocean acidification takes place. The activity of tiny plankton affected by the increase in the world’s ocean acidity may cause the global average temperature to be 1 degree Fahrenheit above current estimates (Spotts,2013). From this point of view, we can already find the importance of small plankton to the earth, and ocean acidification will become their biggest enemy.
Besides zooplankton can be affected by ocean acidification, phytoplankton can also be affected by ocean acidification. Among the phytoplankton family, it can be said that coral algae are most affected by the adverse effects of ocean acidification. Coral algae can form a calcium carbonate skeleton and help cement reefs. Most coral algae species build shells from calcium carbonate in the form of high magnesium calcite, which is more soluble than aragonite or regular calcite. Under acidified conditions, the area of coral algae has been reduced by 92%, making room for other types of non-calcified algae that can suffocate and damage coral reefs (Bennett, no date). This is the main reason that causes coral bleaching. A lot of coral reefs die because of ocean acidification. It is a double disadvantage because many coral larvae prefer to settle on coral algae when they are preparing to leave the plankton stage and start living on coral reefs. Instead of being hurt by ocean acidification, some phytoplankton is even growing better because of ocean acidification. One of the examples is seaweed. Statistics have shown that in more acidic laboratory conditions, they can reproduce better things, grow taller, and have deeper roots, which is a good thing. Seagrass forms a shallow-water ecosystem along the coast, serves as a nursery for many large fishes, and maybe home to thousands of different organisms.
For phytoplankton, iron is undoubtedly the most important element. Like humans, phytoplankton needs iron to grow. But one of the consequences of ocean acidification will be a change in the availability of iron in marine phytoplankton. Phytoplankton is marine grasses that support the marine food web and account for more than half of marine biomass. Most of the iron dissolved in seawater is bound to organic molecules, which limits the ability of phytoplankton to obtain iron. The availability of iron limits the production of many organisms in the global ocean. The finite iron supply also limits phytoplankton’s removal of carbon dioxide released by humans in the ocean. Phytoplankton production causes carbon to be transferred from the atmosphere to the deep ocean, a process that has removed about one-third of the carbon dioxide released by humans from the atmosphere. But finite iron supplies limit the clearing of large oceans. This greatly affects the filtration capacity of phytoplankton.
The driving factor of ocean acidification is carbon dioxide, and ocean acidification which affects plankton life worldwide is caused by the increase of carbon dioxide concentration in the atmosphere. Therefore, reducing carbon dioxide emissions is the most effective way to reduce ocean acidification. Nowadays, the United Nations Framework Convention on Climate Change provides possible solutions to reduce ocean acidification. But the UNFCCC currently lacks the ability to effectively respond to increasing ocean acidification. For people, the most important thing now is to recognize the harm of ocean acidification caused by carbon emissions. For countries, protecting and restoring the environment is the common responsibility of the country, but the level and form of individual responsibility in each region can vary according to their own national conditions. It’s critical for future climate agreements that to burden and share the responsibility to each country. We should move towards a common goal which is reducing carbon dioxide emissions.
We are now working hard to try to stop ocean acidification and global warming. In December 2015, the adoption of the Paris Agreement has taken the world one step closer to our common goal which is to reduce human-caused carbon dioxide emissions. The provisions of the Paris Agreement require each county to regularly review, update and strengthen these actions. This action gives people hope, but we all know that’s not enough. Everyone should be involved in the action of reducing emissions. Ocean acidification caused by excessive carbon dioxide emissions threatens the balance and security of the entire ecosystem, including human life. People may not care or pay enough attention when those humble plankton are threatened by ocean acidification. But over time, the planktons that affected by ocean acidification may become the greatest threat to humanity in the future. So, now it’s time for us to protect these planktons and reduce carbon dioxide emissions. Because save their lives is also save our lives and our beautiful Earth. Earth is our only beloved planet. We need to create a beautiful living environment for our future generations.
