Biota of Pelagic Zone
Pelagic region constitutes 90 per cent of the total ocean surface and is less rich in species and numbers of organisms than the two regions discussed before. The species of this zone are characteristic. The environment due to the continuity of the sea waters is uniform and stable for the organisms occurring here.
The most abundant pelagic phytoplanktons are still the dinoflagellates and diatoms which are the chief photosynthetic feeders, other are carnivores. Detritus feeders such as sea lilies rise above the sea floor while clams and tubeworms remain burrowed in mud. Sea cucumbers and sea urchins crawl on the floor eating detritus and bacteria and serve as food for the carnivorous brittle stars and crabs.