238U, 235U, 226Ra, 228Ra, 87Rb, 40K, 137Cs, 90Sr, and 3H, except for 232Th (which has extremely low solubility in natural water) are soluble in water so they remain in the ocean for a long time. Several of these materials are used as radioactive tracers in oceanographic studies. The study of radiation status in oceans and oceanographic factors influencing the global distribution of marine water is necessary because pollution from offshore petroleum extraction, radioactive element contamination and climate change among other factors threaten seawater and marine life. Oceans and seas were reported to contain radioactive nuclides, which could be small but significant concentrations of anthropogenic, naturally occurring radionuclides and cosmogenic nuclides. Cosmogenic nuclides, waste from nuclear reactors, industrial discharge and weapon testing are major sources from which these radioactive elements enter the ocean. The exposure of the ocean to radioactive nuclides from the decay series of nuclides 238U, 235U and 232Th; the non–decay series of radioactive nuclides 87Rb, and 40K,; cosmogenic nuclide 14C, 7Be, and 3H (nuclides generated by cosmic ray interactions with upper atmosphere gases from space); and the human–made radionuclides 137Cs, 134Cs, 129I, 90Sr, 239Pu, and 99Tc, may cause harmful biological effects on marine ecosystems and organisms. Phytoplankton are autotrophic microscopic marine algae of the plankton community that are important part of the ocean ecosystems. The release of radioactive elements into seas connected to oceans could cause changes in the exposure of marine biota to ionizing radiation. Marine ecosystems contain a diverse array of living organisms and abiotic processes, including sharks, squids, whales, jellyfish, octopuses, and black swallower. Radiation from the sun (sunlight), temperature, nutrients, soil and water are factors that affect the productivity of terrestrial plants. The availability of soil and water is not the issue for phytoplankton. Oceanographic factors influencing the global distribution of marine life in the ocean, including radioactive sources, sunlight, dissolved nutrients, ocean depth, the kind of predators that graze on marine life, tides, changes in the direction and strength of the wind, current, density gradient, salinity, and temperature, are discussed extensively as they affect the productivity of marine life.