Why are living organisms more common in the littoral zone than in the benthic zone?

a.
the benthic zone has less light penetration.
b.
the littoral zone has a variety of plants.
c.
the littoral zone provides more resources.
d.
all of the above

d. All of the above

Littoral zone is the region in the water body that is near the shore. This region is exposed to receive maximum of sunlight. This region is active region for growth of flora and fauna.This region consists of maximum of atmospheric gases like oxygen and carbon dissolved in water. This facilitates efficient photosynthesis and respiration in plants. Hence, support the growth of variety of plants, which further support growth of faunal species. Benthic zone is located at the bottom region of water body. This gives a substrate to the plant to support their growth but this region receives very less penetration of sunlight. This may lead to decrease in population of plant species, which result in consecutively limited number of faunal species in the benthic zone. Therefore, living organisms are more common in the littoral zone than in the benthic zone.  

the missing space is phylum