The correct answer is - nutrient rich.
The nutrient rich waters that are coming from the bottom towards the shallower waters of the coastal up-welling zones are providing an abundant food source for the marine flora. Since the marine flora has it well and manages to prosper, lots of species of the marine fauna that feed on it are attracted here, and because of the abundance of this species, there's also a big abundance of predators that are finding their pray in here, so all in all they create an ecosystem that is very high in biodiversity.