Final answer:
Overfishing tuna can lead to the depletion of tertiary consumers and a collapse of the food web. It can also cause a radical restructuring of the marine ecosystem.
Step-by-step explanation:
If humans overfish tuna, it can lead to several consequences in the food web. One possible outcome is the depletion of tertiary consumers due to lack of food. This can potentially cause a collapse of the entire food web. Additionally, overfishing can result in a radical restructuring of the marine ecosystem, where dominant species are over-harvested and become minor players ecologically.