Final answer:
Excluding Semibalanus from the tidal zone leads to an increase in biotic factors as competition is reduced and populations of other species can grow.
Step-by-step explanation:
When Semibalanus is excluded from the tidal zone, the correct answer is B) Biotic factors increase. This situation is often related to the competitive exclusion principle, which suggests that two species competing for the same resources cannot coexist at constant population values. If we remove one competitor, in this case, Semibalanus, the other species that compete for the same resources will likely experience reduced competition, leading to an increase in their population as they utilize the newly available resources and space within the tidal zone.