Plankton is filled with marine organisms that actively reproduce or are the product of reproduction, making the planktonic environment very important to the life cycles of many organisms. Holoplankton (an organism that spend its whole life in the plankton) reproduces in the plankton and most meroplankton (an organism that spends part of its life cycle in the plankton) release larval stages into the water column.   Below is an example of a larval form of a brittle star.  Holoplanktonic and some meroplanktonic organisms have specialized features that make reproduction in the water column more efficient. For more information about reproduction for particular organisms, see the introduction page with numerous phyla. 
 
 

Sexual reproduction is found in a variety of planktonic as well as benthic organisms.  Some organisms use specialized appendages, which grasp onto their respective partners preventing them from drifting away during copulation.  Other holoplanktonic and meroplanktonic invertebrates release sperm into the water column; females take up the sperm to fertilize their eggs.  Some organisms release eggs and sperm simultaneously into the planktonic environment in order to increase the likelihood of  fertilization.  This release of sperm and eggs can be triggered by environmental, mechanical, or chemical cues.   Also, a few benthic organisms have developed reproductive body parts that break off and swim into the water column.  Brooding of eggs on the body in a sac or release of egg cases into the plankton aids in the development of several invertebrates.

Asexual reproduction can also occur in planktonic forms but seems to be less common in marine invertebrates.  Asexual reproduction usually occurs through fission, or budding.