Hey,

The  Benthic zones of oceans is the region of the ocean which is the closest to the ocean bed which is the bottom of the ocean.

The pelagic zone is the surface of the ocean that is the uppermost layer of the ocean.

In terms of diversity the pelagic zones are rich in diversity as compared to benthic zone and light is less in benthic zone as compared to pelagic zone.

I hope this helps.

All the best!