PHYTOPLANKTON: PRIMARY

Primary Producers for the World

By: Alexandrya Robinson, UHM MOP Student

Under the microscope, a single drop of sea water is teeming with life. In just one liter of ocean water, there can be upwards of a million different phytoplankton and half a million zooplankton! That is just a fraction of the billions of different bacteria and viruses. So many different things live inside just a small amount of water, and these microscopic organisms form the basis of the marine food chain. This food chain starts with phytoplankton which are drifting photosynthetic algae, plants, and bacteria that feed both small and large organisms. There are different kinds of phytoplankton that support the diets of different organisms. The major kinds of phytoplankton include algae, cyanobacteria, coccolithophores, diatoms, and dinoflagellates.

This is Prochlorococcus, a type of marine cyanobacteria. Cyanobacteria are algae that live in both fresh and saltwater. This species, while incredibly small, supports a host of zooplankton species including meroplankton (organisms that spend only a portion of their life in the planktonic stage) and different species of zooplankton.

This is an example of a diatom, an algae with a silicate housing. Diatoms are one of the most abundant species of phytoplankton and produce high levels of oxygen. They also support fish and crabs as a food source in both their larval and adult stages.

Primary Producers for the World

By: Alexandrya Robinson, UHM MOP Student

This is a species of coccolithophore, which have calcareous skeletons (made of calcium carbonate). Coccolithophores are the most abundant group of phytoplankton. In fact, one out of every four breaths you take was supplied by coccolithophores! These species feed fish, meroplankton, and zooplankton.

Dinoflagellates are propelled by their distinctive flagellae. Other non-photosynthetic microorganisms feed on dinoflagellates as well as small fish and zooplankton.

But phytoplankton predators are not only small fishes. Species as large as giant clams and baleen whales will filter feed on phytoplankton. Many species rely on phytoplankton directly or on the species that eat them. As a result, these microscopic organisms are an unsung but integral part of any ocean community.