Answer:
a. Sunlight cannot penetrate through the ash clouds. thus photosynthesize won't occur. so the food chain will begin to collapse from the producer and primary consumer. owls will be out thinking that it's night. they will catch fish resulting in an imbalanced ecosystem. the aquatic population will decrease. then it's the doom days for owls. they will emigrate or will die.
b. the ecosystem will restore. that's how nature works.