Answer:
The kelp population would decrease: sea otters eat urchins, and urchins eat kelp.
Step-by-step explanation:
The diagrammatic illustration in this question is showing a food web made up of a variety of species feeding on one another. As shown in the food web, sea otters are one of the top predators that can eat a wide variety of organisms.
Sea urchins feed directly on kelp, however, the population of sea urchins can be controlled by sea otters which feed on sea urchins. Hence, if population of sea otters declined, more sea urchins will be available to feed on the kelp population, hence, will DECREASE.