Nektonic animals are those that swim and migrate freely, e.g., adult fishes , whales , and squid . Planktonic organisms, usually very small or microscopic, have little or no power of locomotion and merely drift or float in the water. Seafloor areas called hydrothermal vents , with giant tube worms and many other unusual life forms, have been intensively studied by marine biologists in recent years.
Bacteria are abundant in upper waters and in bottom deposits.
The scientific study of marine biology dates from the early 19th cent. Fla. Research has been furthered by unmanned and manned craft, such as the submersible Alvin. See also oceanography . Listing from Electric Library , a pay service. Copyright 2001 Infonautics Corporation .