pelagial
/pɪˈleɪdʒ(ɪ)əl/Ecology
noun
The main body of water of a lake or sea, contrasted with the littoral and benthic regions.
adjective
Of, relating to, or designating this region.
Origin
Late 19th century; earliest use found in Science. From classical Latin pelagius of or belonging to the sea + -al, perhaps after German pelagial.