They form the bottom of the food chain in the sea and are very important in ocean food webs. Nets Oceanographers use nets to catch these small creatures and study them. The nets are of a much finer mesh than fish nets, as the mesh openings must be small enough to concentrate the plankton while still allowing water through. The nets are attached to the hydrowire and towed behind the ship. This leaves them free to collect and observe without the danger of floating too far from the boat or sinking too deep.
Researchers can now use high technology submersibles to study creatures that live in the deep sea.
Diatoms have cell walls made of silica, and many form long chains of cells. Blooms of these phytoplankton can be seen from space with satellites, showing up as a milky white color in the surface ocean. These tiny crustaceans the size of a rice grain are estimated to be most numerous multicellular animals on earth. These zooplankton are important source of food for many marine mammals and seabirds. They are especially well known in the Antarctic where they are an important part of the food web.