New Hampshire PBS
   share this page
NATUREWORKS!
Home     About     Watch     Nature Files     Teachers     Order DVD     Contact
 

Plankton

Plankton is the foundation of the ocean food web. The word plankton comes from the Greek word "planktos" which means drifting.
   Food For All

ShoresOne of the most important plants in the sunlit zone is also the smallest. Phytoplankton are organisms that float on or near the surface of the water. Most are rounded and single-celled. All phytoplankton use photosynthesis for their energy, but some get additional energy by consuming other organisims. The most common phytoplankton are diatoms and dinoflagellates. Diatoms are single-celled algae. They often join together in long chains.

phytoplanktonDinoflagellates are small organisms with two tails or flagella. Dinoflagellates come in all kinds of shapes and sizes. Some have shells and some don't. Not all dinoflagellates rely only on photosynthesis for all their energy. Some wrap themselves around food and absorb it. Some dinoflagellates can make light using bioluminescence.

phytoplanktonPhaeophyta
or brown algae are another type of phytoplankton. Blue-green algae or cyanobacteria are also phytoplankton, although they are very unique. They photosynthesize, but some also use nitrogen for their energy. They are nitrogen fixers. They change free nitrogen into nitrates which are used by the cyanobacteria and by other plants in the ocean. Phytoplankton are the base of the ocean's food web and are the food source for zooplankton.

    Going With the Flow
Zooplankton are ocean animals that don't swim at all or are very weak swimmers, and they drift or move with ocean currents. They can be found in the sunlit zone and in deep ocean waters. Zooplankton range in size from tiny microbes to jellyfish, although most zooplankton are tiny, single-celled organisms. There are two types of zooplankton. Permanent or holoplankton will always be zooplankton. Temporary or meroplankton are made up of the larvae of fish, crustaceans and other marine animals. If they survive, they will grow into nekton or free-swimming organisms.
   Room to Grow
phytoplanktonForaminifera are tiny single-celled, shell-covered organisms, usually between a millimeter and a centimeter in diameter. As they grow, they add chambers to their shells. Depending on the species, the shell may be made of sand, calcite or organic matter. They move and catch their food with thin, hair-like extensions called  pseudopodia. When foraminifera die, their shells sink to the ocean floor and form an ooze. It is estimated that 30 percent of the ocean floor is made of the shells of foraminifera. Both limestone and chalk come from foraminifera! 
   Like a Rock
Radiolarians are small, round, shell-covered organisms. They make their shells with silica. Silica is used in making glass and can be found in minerals like quartz. They get the silica from the ocean. Radiolarians have long, sticky tentacle-like arms called pseudopodia. They stick their pseudopodia out of holes in their shells to catch phytoplankton as it floats by. When radiolarians die, their shells sink to the bottom of the ocean. Over time, if enough shells sink together,  the skeletal remains can become sedimentary rock!
 
    Hairy Moves
ShoresCiliates have cilia or little hair-like extensions all around their bodies that they use to move and to catch food. There are over 8,000 species of ciliates., including paramecium. They live in salt and freshwater. Some are free swimmers, others attach themselves to organisms or objects, and some are parasites. Only the free swimming ones are considered zooplankton!
    Waving the Flag
Zooflagellates, like dinoflagellates, have long flagella. They either absorb their food or engulf it in food vacuoles or pockets. They live under many different conditions. Some are parasites and can be found in the digestive tracts of animals like the cockroach and termite; others are free swimmers. The free swimmers are zooplankton.
    Jelly Belly
ShoresJellyfish are also zooplankton. Jellyfish are basically big stomachs and long tentacles!  Their tentacles have stingers on them and they use them to catch and paralyze food and carry it to their stomachs. They move in the water by pumping their stomachs. They mostly move up and down in the water and let the currents carry them from side to side.
    The More the Merrier
ShoresSiphonophores like the Portuguese man-of-war look like jellyfish but they are not. They are really groups or colonies of  animals. Each organism in the colony has a special niche or role. Some form the tentacles, and some form the mouth and stomach.
    Going Buggy
ShoresCopepods are sometimes called the insects of the sea because there are so many of them - about 10,000 species! They can be found in fresh and salt water. Copepods are very small, usually not more than a few millimeters long. The largest copepod, the Pennella balaenopterae, lives on the finback whale and can grow to be over a foot long!  Copepods are crustaceans. They have two antenna, a shell and segmented bodies. They graze on phytoplankton and zooplankton. Copepods are the largest source of protein in the ocean! 
    Good Eats!
ShoresKrill, one of the ocean's smallest animals, is dinner for one of its largest, whales!  There are about 82 species of krill, ranging in size from less than a quarter of an inch long to two inches long. Krill are crustaceans like copepods. They often have bioluminescent organs. They can be found in the sunlit zone and in the twilight zone.

Images
CC BY 2.0

CC BY 3.0
CC BY-SA 3.0.

     

 


Advertisement: