Which of the following is true about the relationship between sea otters and kelp forests?

The assertion regarding the relationship between sea otters and kelp forests indicates that sea otters play a crucial role in maintaining the health of these ecosystems through their predation on herbivores, specifically sea urchins. In a balanced marine ecosystem, sea otters feed on sea urchins, which are known to graze heavily on kelp. When sea otter populations are healthy, they effectively control the sea urchin population, allowing for the growth and proliferation of kelp forests. This interaction illustrates a classic example of a keystone species, where the presence and activity of sea otters directly enhance the biodiversity and stability of the kelp forest environment.

In situations where sea otters are removed or their populations decline, the unchecked sea urchin populations can lead to overgrazing of kelp, resulting in "urchin barrens" where kelp is severely diminished or entirely absent. Therefore, the health of kelp forests is intricately linked to the presence of sea otters, making this relationship vital for marine ecosystem health.