User:Bryanhuynh8/Ocean acidification

Ocean acidification is the decrease in the pH of oceans on Earth. Between 1950 and 2020, the Earth’s oceans have decreased in pH from 8.15 to 8.05. The main cause of ocean acidification today is due to human activities leading to an increase in carbon dioxide. Over the past 200 years, the rapid increase in anthropogenic CO₂ (carbon dioxide) production has led to an increase in the acidity of the Earth’s oceans. When CO₂ interacts with water, it forms carbonic acid (H₂CO₃) which then breaks down into H⁺ (hydrogen ions) and bicarbonate ions (HCO₃^-). Some of the bicarbonate ions will turn into carbonate ions (CO₃^2-), releasing more hydrogen ions. Releasing hydrogen ions into the water lowers its pH leading to higher acidity. Calcifying marine organisms and corals are at risk because calcium carbonate is used to build their skeletons and shells. If the water pH is low enough, the calcium carbonate structures of marine organisms and corals will dissolve.

A pteropod showing negative effects of ocean acidification such as its shell is dissolving, weak spots, and scratches.

Cause

Ocean acidification is mainly caused by an increased concentration of carbon dioxide in the atmosphere. One of the main causes of ocean acidification is when humans burn fossil fuels. When these fossil fuels are burned for energy, they release CO₂ into the atmosphere as a byproduct of combustion which is a significant contributor to the increasing levels of CO₂ in the Earth’s atmosphere. When CO₂ is in the atmosphere, a portion of it naturally dissolves into the ocean’s surface layer as part of the carbon cycle. When it dissolves, it leads to a chemical reaction that forms carbonic acid which makes the ocean more acidic. Agriculture also contributes indirectly to ocean acidification primarily through two main mechanisms. Nutrient runoff is a main driver of this. Specifically, the use of fertilizers containing nitrogen and phosphorus. During periods of rain, these nutrients can wash off the fields and enter nearby water bodies like rivers, lakes, and oceans. Overabundant nutrient runoff may result in the proliferation of algal blooms. As these algae perish and break down, they deplete oxygen and emit carbon dioxide (CO₂) into the water, thereby elevating its acidity. Inappropriate agricultural techniques, such as excessive tilling or deforestation, have the potential to cause soil erosion. As soil erodes, it transports sediment and organic material into adjacent water sources. This sediment buildup can suffocate marine ecosystems such as coral reefs and seagrass beds. Moreover, the decomposition of organic matter releases CO₂, exacerbating water acidity. Deforestation also plays a part in ocean acidification. Since trees and plants absorb CO₂ from the atmosphere when forests are cleared due to urban development or agricultural purposes, the levels of CO₂ increase due to a decrease in the ability of the land to absorb it.

Effect

The negative effects of ocean acidification will only grow unless CO₂ emissions are to be heavily reduced. The acidification process disrupts the capacity of marine creatures like corals, shellfish, and plankton to construct and uphold their calcium carbonate-based shells or skeletons. Consequently, their structural integrity weakens, rendering them more susceptible to predation and environmental pressures. Disruption of the food chain is also a possible effect as many marine organisms rely on calcium carbonate-based organisms at the base of the food chain for food and habitat. This can potentially have detrimental effects throughout the food web and potentially lead to a decline in availability of fish stocks which would have an impact on human livelihoods. Coinciding with these points, ocean acidification could also have significant economic consequences mainly for industries reliant on marine sources such as fisheries, aquaculture, and tourism.

History

Research in Ocean Acidification began in 1909 with the creation of the pH scale by S. P. L. Sørensen. Early interest in pH revolved around biological systems. By the mid-20th century, it was clear to the United States that there was a lack of knowledge regarding ocean CO₂ chemistry which eventually led to the formation of the Geosecs program. The program initially experienced significant errors that lasted until 1981. Despite this, the Geosecs program conducted surveys of the Atlantic, Indian, and Pacific Oceans. Late in the 20th century, ocean science turned toward international policy concerns. In 1999, “Our Changing Planet: A US Strategy for Global Change Research”, and the first IPCC Scientific Assessment in 1990 included projections of future CO₂ emissions. By the mid-1990s, scientists became concerned about the potential impact of carbonate levels and increasing CO₂ levels on ocean pH. Concerns about coral reef calcification grew as the understanding of CO₂ grew. Experimental results in the year 2000 suggest that by 2065, coral reefs will experience a significant drop in levels of calcification. Further studies have also indicated future levels of coral reef calcification will decrease. A study done in 2020 argues that ocean acidification is not only negatively affecting marine life, but also human health. Food quality, respiratory issues, and human health are all negatively affected by ocean acidification.