Explain in steps how overfishing of species like tuna, cod, and sardines can affect the kelp population of the bay ecosystem.

Those fish species are removed / weakened so the organisms that the fish eat have less natural predators and increase in population. They need to eat more kelp in order to sustain their population, resulting in a loss of kelp as there is suddenly more of a demand for it then the kelp can grow. All because the predators were removed from the food chain.