Why was chthamalus unable t compete with semibalanus at the lower depths?

Chthamalus was unable to compete with Semibalanus at lower depths primarily due to the latter's superior competitive abilities and tolerance to submersion. Semibalanus can withstand harsher conditions, such as increased competition for space and resources, which gives it an advantage in these environments. Additionally, Semibalanus grows faster and can occupy space more effectively, outcompeting Chthamalus in the lower intertidal zones. Consequently, Chthamalus is often restricted to higher elevations where it can survive better despite its weaker competitive abilities.