USA Biology Olympiad (USABO) Practice Exam

Which marine community would likely be least affected by a significant reduction in sunlight due to a volcanic eruption?

1. Coral reef community

2. Intertidal zone community

3. Deep sea vent community

4. Estuarine community

The correct answer is: Deep sea vent community

The deep sea vent community is particularly adept at thriving in conditions that have limited sunlight, making it the least affected by a significant reduction in light caused by a volcanic eruption. This community relies on chemosynthetic organisms, particularly bacteria, which harness energy from chemical reactions involving substances such as hydrogen sulfide emanating from hydrothermal vents instead of relying on photosynthesis. In contrast, the other marine communities are more closely tied to sunlight. Coral reef communities depend on symbiotic relationships with zooxanthellae, which require sunlight for photosynthesis. The intertidal zone community also relies on light, as many organisms there are photosynthetic. Estuarine communities, while somewhat variable, have similar dependencies on light due to the presence of plants and algae that require sunlight for growth. Therefore, the deep sea vent community stands out as the most resilient to changes in light availability.