Researchers have revealed the extent to which zooplankton in seas and oceans are affected by the deterioration in the quality of the materials they feed on due to the increasing alkalinity of seawater, as one of the proposed solutions to make the oceans more capable of absorbing carbon dioxide.

Oceans absorb about 25% of carbon dioxide emissions, making them an important carbon sink and placing them on the table of proposed solutions to address the climate crisis. But there are many challenges facing the oceans, especially in light of the worsening greenhouse effect and the increase in greenhouse gas emissions in the atmosphere, which puts pressure on the oceans and affects their physical properties.

How do the oceans absorb carbon dioxide?

Simply put, water generally consists of hydrogen and oxygen. When the oceans absorb large amounts of carbon dioxide, the pH of the water decreases, which means its acidity increases. This occurs from the interaction of water with carbon dioxide, resulting in the formation of carbonic acid, which contributes to the acidification of ocean water. This was one of the challenges faced by scientists when they wanted to enhance the role of the oceans in absorbing carbon dioxide.

Increasing alkalinity

The proposal to increase the alkalinity of seawater involves adding certain minerals such as carbonates and silicates. This, in turn, contributes to the oceans' ability to absorb larger amounts of carbon dioxide in a process known as "Ocean Alkalinity Enhancement" (OAE), which mimics the natural weathering of rocks by adding rocks or some of their dissolution products to seawater.

What about living organisms?

There were many questions about how living organisms respond to increased water alkalinity. This prompted a research group from Germany to study the potential impacts on the marine food web, including marine creatures for the first time, and they published their results in the journal "Science Advances" on December 6, 2024.

The researchers conducted the experiment off the Canary Islands, using large test tubes, and lowered them into the sea, thereby isolating 8 cubic meters of the water column. After that, they added different concentrations of some substances, such as sodium carbonate and bicarbonate. They continued to monitor for 33 days the impact of alkalinity on zooplankton, which play a crucial role in transferring energy through the marine food web. And they observed the responses in zooplankton in terms of biomass, productivity, and others.

The researchers found that the condition of the zooplankton was stable despite the chemical changes that occurred in the surrounding environment. They also observed a deterioration in the quality of the food materials that the zooplankton feed on; however, the zooplankton were not affected.

The authors of the study believe that ocean alkalinity could be an effective means to mitigate the worsening of global warming, but we need more research to examine the impacts of this approach on other marine organisms.