The open ocean is the largest habitat on Earth, but life is sparse because of low nutrient concentration and great depth. The open ocean is the largest habitat on Earth, but life is sparse because of low nutrient concentration and great depth. In the open ocean, diversity is high but the number of individual per species is low. The only seaweed in the open ocean sea is Sargassum gulfweed. The major phytoplankton are diatoms, dinoflagellates and coccolithophores and the major zooplankton are foraminifera and radiolaria.
Diatoms dominate the shallow coasts, but decrease in abundance seaward.
Top predators are mackerel, squid, jellyfish, tuna, porpoise, shark and man.