What are two harmful effects on aquatic systems resulting from the increase in the human population in coastal areas?

The best way to tell its true color is to look at the minerals streak

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.