Biota of the Neritic Oceanic Zone
This zone constitutes 75 per cent of the total oceanic area and is relatively rich in species and high in productivity owing to factors such as penetration of light to considerable depths and high concentrations of nutrients. Communities in this region are both richer and more diverse compared to those of the open ocean. No other region has such a variety of life not even 'the tropical rain forests. The most productive phytoplanktons are the dinoflagellates and diatoms, though red, brown and green algae attached to the bottom in the shallow regions may be significant. The zooplanktons are usually similar to those of the pelagic zone though some purely open-sea species are replaced by neritic species.
Temporary zooplanktons are more numerous here than in the open sea. Nekton in the ocean over neritic zone or the continental shelf are diverse and commonly known, for they include almost all commercial species .as well as whales, seals, sea-otters, sea snakes and large squids. Fishes are numerous and include several shark species as well as herring-like species (sardine, herring) cods and their relatives (haddock and pollack), sea trout and salmon, flat fish (sole, halibut) and mackerals including tuna and bonito. The benthic part of the neritic zone is called the sublittoral zone which has a wide variety of animals among which are clams, shrimps, snails, lobsters, crabs, sea cucumber, starfish, brittle stars, anemones, sponges, bryozoa, annelids and foraminifera. These animals exhibit more diversity than those of the deeper waters, since the physical factors here are more variable. The bottom may be rocky, sandy or muddy and the temperature difference in the sublittoral zone of this region is greater as compared to the deeper ecosystems. The difference in- the physical environment is reflected in the benthic community occurring here.