Final answer:
Primary consumers in secondary succession on a volcanic island play a role in establishing a stable ecosystem by acting as pioneer species and contributing to the formation of soil.
Step-by-step explanation:
In the process of secondary succession on a volcanic island, the primary consumers play a key role in establishing a stable ecosystem. They act as pioneer species, the first species to colonize the new land or disturbed area. These pioneer species, such as plants and insects, help break down the volcanic rock and contribute to the formation of soil. As the soil develops, other organisms like secondary consumers and climax community species can establish themselves in the ecosystem.