What is Ocean Acidification?

Ocean Acidification is the decrease in pH levels in the ocean throughout an extended period of time.

Important Knowledge

40 gigatons of emissions have been released into the atmosphere from 2008-2017. The process of the absorption of CO2 between the surface of the ocean and the atmosphere has stayed constant for millions of years. However, in the past 150 years, humans have drastically increased the amount of CO2 released in the atmosphere due to modern technology and other causes. The ocean has absorbed about 29 percent of that additional CO2 pollution. 

The Process of Ocean Acidification

First, carbonic acid forms. Then, the carbonic acid breaks apart, which produces bicarbonate ions and hydrogen ions. Basically, the CO2 enters the ocean and dissolves in the saltwater. Ocean acidification results from an increased concentration of hydrogen ions and a reduction in carbonate ions due the the absorption of increased CO2. Some sea life need carbonate ions to grow their shells, so many marine species are in danger. (We have diagrams of this process in the diagrams section)

The Effect of Ocean Acidification

The ocean surface waters are 30% more acidic than they were at the start of the industrial era. This means that the pH of surface waters has decreased 0.1 pH units. Ocean acidification is occurring faster than at any time in the last 66 millions years. By the end of the century, surface waters could be more than twice as acidic as they were at the end of the last century if we are not able to reduce our carbon emissions. 

Ocean Acidification is effecting marine life. Coastal and marine ecosystems are struggling because of climate change. Ocean acidification combined with other climate impacts such as warming waters, deoxygenation, melting ice, and coastal erosion seriously threaten many marine species. Acidification reduces carbonate ions which provide the essential pieces that some organisms need to make their shells and skeletons. This is reducing the chances for their offspring to survive. 

The entirety of the food chain is put at risk when anything apart of it are in danger. Studies show that algae and seagrass could potentially benefit from higher CO2 because they require CO2 to perform photosynthesis. Our experiment will confirm or deny this theory. This process is similar to plants on land such as trees. If we grow more green algae in the ocean, the process of ocean acidification could slow down. Our project will help us understand these ideas better.

Acidity

Acidity is a measurment of the concentration of hydrogen ions in ocean water. It is measured in units of pH.

CO2 Concentrations Drive Rising Temps and Acidification

The increasing CO2 in the atmosphere is bringing up the temperature of ocean surface waters and driving more ocean acidification. Despite being two separate processes, warming and acidification interact negatively with marine ecosystems. The rates of change in the ocean are different everywhere based off of temperature, latitude, and depth. The rate that CO2 is absorbed decreases when the water temperature increases. This means polar surface waters typically acidify more quickly than those at different latitudes, and generally warmer areas of the ocean tend to release CO2 rather than absorb it. For example, the Bahamas cannot absorb as much CO2 and if anything is releasing it. Somewhere like Alaska is more acidic because it absorbed much more CO2. Rising surface water temperatures in other areas (often the tropics) are slowing down the transfer of carbon between surface waters and deep waters.

Wind

The wind plays an incredibly important role because it mixes the deep waters with the surface waters. By mixing these waters, the CO2-saturated areas get moved to deeper parts of the ocean. The surface temperatures are rising which means it is progressively becoming even more challenging for the wind to mix the layers. If the layers don't mix, they sit on top of each other (increasingly stratified). Deoxgenation is when the lower layers of the ocean have less oxygen. In warmer areas, the surface waters have absorbed more CO2 and cannot uptake anymore. 

pH Scale

The range of the pH scale runs from 0 to 14. When the pH is 7, it means it is neutral. If the pH is higher than 7, it is basic or alkaline. Finally, if it is lower than 7, it is acidic. The pH scale measures the proportion of free hydrogen and hydroxyl ions in water.

CO2 in Seawater

CO2 is already naturally in the atmopshere and dissolves in saltwater. When water and carbon combine, they form carbonic acid. Carbonic acid is not a strong acid and it disassociates into hydrogen ions and bicarbonate ions. The average pH in the ocean is 8.1, which is basic or alkaline. When the ocean uptakes CO2, the pH decreases, so the ocean is more acidic.