According to estimations, the ocean takes up roughly the same amount of CO2 annually as all of the world's forests (Jet Propulsion Laboratory, 2022). Scientists and biologists are worried about how much CO2 the ocean takes in. As CO2 dissolves in the oceans, the seawater's chemistry changes. It becomes more acidic and has lowered its pH by up to 30% over the previous 200 years (Fitzer, 2019). Crabs, clams, and other shellfish have a hard time growing their shells to the necessary strength because they absorb CO2. The global supply of shellfish is facing significant challenges due to the increasing acidity of the oceans (Fitzer, 2019). These organisms need their shells as protective habitats, as the acidity of water can kill them (Jet Propulsion Laboratory, 2022).
Figure 1. Shellfish Impacts in Various pH Level (NOAA Fisheries, 2019).
What happens to shellfish?
Shellfish include organisms like mussels, oysters, and corals that create calcium carbonate shells and skeletons (Fitzer, 2019). They form their protective shell structures and filter calcium and carbonate from the water to produce hard minerals like calcium carbonate. Researchers from Milford Lab collected samples from two systems of experimentation to investigate the effects of increasing acidity in the water on shellfish (NOAA Fisheries, 2019). In the first experiment, "seed" oysters that were seven months old were the subjects. Scientists at Milford examined respiration, growth, and feeding in two groups of oysters—one fed and the other unfed—over the course of ten weeks in November and December 2018 at three distinct pH levels. The study discovered that oysters from the low-pH treatment had shell weights that were much lower than those of oysters kept at the standard pH level of the water (NOAA Fisheries, 2019). The Olympia oyster and the Pacific oyster were the subjects of research by additional researchers from the University of Washington School of Aquatic and Fishery Sciences (DiNicola, 2020). Researcher Laura Spencer found that when subjected to acidity and warmth throughout the winter, Olympia oyster adults were found to be relatively resilient. This resilience can help the future oysters by enhancing their chances of survival. In another study, adult Pacific oysters were similarly exposed to lab circumstances that were acidic; however, they did not survive as well in their experimental conditions as Olympia oysters did (DiNicola, 2020).
Effects of Ocean Acidity on Shellfish Causes Chain Reaction
The lack of a protective shell can affect growth of the shellfish along with the overall survival of the organism. The weakened shells make the shellfish more susceptible to predation and enable them to thrive in their habitats. The consequences extend beyond the individual organism, affecting entire ecosystems and the human communities that depend on them. Firstly, there will be an increase in dead zones. Shell-fish are filter-feeding organisms and without these, nutrients will start to accumulate. This event is known as Eutrophication. Eutrophication occurs when there is a rapid entry of nutrients, usually due to fertilizer runoff or waste. In the absence of shellfish, bacteria and algae will consume the nutrients, as well as the oxygen leaving the rest of the organisms with no oxygen. A no oxygen area is called the dead zone, where many aquatic organisms will die. Moreover, the food web will collapse. Many organisms in the marine ecosystems depend on each other for food. Shellfish are a key in this food web. As the shellfish population decreases, species such as Atlantic cod, salmon, pollock and coastal waterbirds will lose their main food source and eventually cause a decline in these populations as well.
Figure 2. Ocean Acidification Impact Pathway for Shellfish (EPA, 2015).
Furthermore, the economy will suffer. Acidification reducing the size and abundance of shellfish results in fishermen experiencing decreases in harvest and at the same time, consumers facing changes in prices. Next steps include addressing the issue. Advocating and addressing the effects acidification has on aquatic creatures and humans is essential. Day to day actions can be taken to reduce overall climate change issues which will also reduce ocean acidification. Simple actions such as taking the transit, carpooling, and reducing waste can all help with this situation.