Researchers developed a model to predict the effect of “business-as-usual” CO2 emissions on our oceans by the end of this century. Conditions based on this business-as-usual model were used to evaluate the net ecosystem calcification (production of calcium carbonate) in seawater tanks containing representative communities to replicate the southern Great Barrier Reef. What variables were likely altered in this experiment to estimate the conditions of the year 2100?

Verified step by step guidance

1. Identify the primary variable of interest in the experiment, which is the concentration of CO2. This is because the experiment aims to simulate the effect of increased CO2 emissions on ocean chemistry.
2. Consider the impact of increased CO2 on ocean pH. Higher CO2 levels can lead to ocean acidification, which is a decrease in the pH of the ocean. This change in pH would be a critical variable to control in the experiment.
3. Examine the effect of altered pH and CO2 levels on calcium carbonate solubility. Since the experiment measures net ecosystem calcification, understanding how changes in CO2 and pH might affect the solubility and hence the availability of calcium carbonate for biological processes is essential.
4. Assess other environmental factors that could be influenced by increased CO2 levels, such as temperature and salinity. These factors could also impact the overall health of the marine ecosystem and the calcification process.
5. Control and monitor all these variables (CO2 concentration, pH, temperature, salinity) to create a simulated environment that accurately represents the predicted conditions of the year 2100 under a business-as-usual scenario.

Key Concepts

CO2 Emissions and Ocean Acidification

Increased CO2 emissions lead to higher concentrations of carbon dioxide in the atmosphere, which subsequently dissolves in ocean water, forming carbonic acid. This process lowers the pH of seawater, resulting in ocean acidification. Ocean acidification negatively impacts marine organisms, particularly those that rely on calcium carbonate for their shells and skeletons, such as corals and mollusks.

Net Ecosystem Calcification

Net ecosystem calcification refers to the balance between the processes of calcification (the production of calcium carbonate by organisms) and dissolution (the breakdown of calcium carbonate). In marine ecosystems, this balance is crucial for maintaining healthy coral reefs and other calcifying organisms. Changes in environmental conditions, such as pH and carbonate ion concentration, can significantly affect this balance.

Experimental Variables

In scientific experiments, variables are the factors that can be changed or controlled to test their effects on the outcome. In the context of this study, variables likely altered include CO2 concentration, temperature, and nutrient levels in the seawater tanks. By manipulating these variables, researchers can simulate future ocean conditions and assess their impact on net ecosystem calcification.