Plankton
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Plankton are the diverse collection of organisms that drift in water but are unable to actively propel themselves against currents. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales.
Marine microplankton and mesoplankton Part of the contents of one dip of a hand net. The image contains diverse planktonic organisms, ranging from photosynthetic cyanobacteria and diatoms to many different types of zooplankton, including both holoplankton (permanent residents of the plankton) and meroplankton (temporary residents of the plankton, e.g., fish eggs, crab larvae, worm larvae).
Plankton (organisms that drift with water currents) can be contrasted with nekton (organisms that swim against water currents), neuston (organisms that live at the ocean surface) and benthos (organisms that live at the ocean floor).
Some marine diatoms — a key phytoplankton group
The amphipod Hyperia macrocephala – part of the zooplankton
Archaea
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Archaea is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotic. Archaea were initially classified as bacteria, receiving the name archaebacteria, but this term has fallen out of use.
Archaea were discovered in volcanic hot springs. Pictured here is Grand Prismatic Spring of Yellowstone National Park.
The ARMAN are a group of archaea discovered in acid mine drainage in the early 2000s.
Sulfolobus infected with the DNA virus STSV1. Bar is 1 micrometer.
Archaea that grow in the hot water of the Morning Glory Hot Spring in Yellowstone National Park produce a bright colour