This is ignu question  of Ability Enhancement Compulsory Course(AECC) On Envirinmental Studied book. See the Page no-58.

Benthic zone is part of ocean layer which describes the layers closer to the bottom of the water body ,and pelagic zone is layer which includes the free water column that interacts with the surfaces layers of the water body.
Differences
Benthic: Referring to the sea, benthic zone start at the shoreline and extends into deep waters , away from landmass . It is noticed that there isnt specified depth to this zone ,as it could vary from few inches as in a stream to several 1000's of meters as in the open ocean. Since light cannot penetrate this depth, this zone lacks the ability to photosynthesis as its energy source.
Pelagic zone:: this zone is the uppermost layers of a water body ,especially referring to the ocean, interacts directly with the atmosphere .
Physical and chemical properties of this zone vary greatly because of the vastness of this area ,which extends from the uppermost waters down to the deeper layers near the benthic zone of a water column.
This zone can be divided into several sub layers that extend the top to bottom.

Hello aspirant,

Following are the differences between Benthic and Pelagic zone:

• Benthic zone is the layer closer to the bottom of a water body, whereas pelagic zone refers to the uppermost layers of a water body.

• Organisms that live in the benthic region are coined as ’benthos’, and organisms found in the pelagic zones are referred as pelagic organisms.

• Referring to the open sea, benthic zone is characterized by low temperatures, low dissolved oxygen levels, low/no light, and high pressures. However, there is a gradient of these in the pelagic zone from top to bottom.

• If we compare the diversity in these zones, resource rich pelagic waters harbor higher diversity than the benthic zone that has lower resources.

• Photosynthesis does take place in the epipelagic zone, but benthic zone does not get enough light for this.

• Pelagic food webs are powered by photosynthesis whereas benthic communities are normally powered by detritus drifted from the upper layers.

• No photosynthetic organism can be found in the benthic region; it is dominated by detritivores and scavengers. In the pelagic zone, photosynthetic organisms as well as active predators are dominant.

• All most all the creatures in the benthic zone are bottom-dwellers or sessile animals whereas all the creatures in the pelagic zone are free-living.

• Example: Benthic- crabs, fishes, prawns, and lobsters ; Pelagic- mackerel, sardine, tuna

Good Luck

Hello Aspirant !

Benthic zone includes the rooted submerged plants and animals. The animals like crabs, fishes, prawns, and lobsters will remain on the bottom of the oceanic layer.

Example : Benthos include worms, clams, crabs, lobsters, sponges, and other tiny organisms that live in the bottom sediments.

Whereas,

In Pelagic zone plants are in the form of rooted micro algae. This includes the phyto and zooplankton. The mackerel, sardine, tuna are the commonly found fish species in the zone.

Example :  Organisms living in this zone are plankton ,floating seaweed , jellyfish  , tuna ,many sharks and dolphins  .

Hope it helps !