User:Tiffanylujan/Heterotrophic picoplankton

Background
Heterotrophic picoplankton are microorganisms that use organic nutrients or carbon from sources other than the sun for growth. Plankton are categorized by three sizes: microplankton, nanoplankton, and picoplankton. Picoplankton are more dominant at lower latitudes and found to have seasonal preference, or more rapid growth rate, for spring and summer. The higher growth rates of picoplankton makes them an important part of the aquatic food web. Half of all bacteria and archaea heterotrophic production is on the surface layer of the water where sunlight is present. Characterization of plankton communities can be carried out by AUV gliders with optical and acoustic sensors, but picoplankton communities are typically monitored using sequencing, microscopy, or flow cytometry.

Heterotrophic picoeukaryotes
Heterotrophic picoplankton are composed of prokaryotes and single celled eukaryotes referred to as protists. Heterotrophic protists consume bacteria and other small microbes for energy. Protists include a wide variety of species such as Picophagus flagellatus and Symbiomonas scintillans, although many species are unknown due to the difficulty of culturing them in a laboratory setting. Characterization is done by sequencing using an 18S tag within the ribosomal RNA.

Heterotrophic picobacterioplankton
Heterotrophic bacteria and archaea are measured in aquatic systems using fluorescent nucleic acid stains and flow cytometry to visualize. Prokaryotic populations are categorized based on high nucleic acid fluorescence (HNA) or low nucleic acid fluorescence (LNA). The HNA group has been found to be primarily composed of Bacteroidetes within the polar circle while HNA has been found to be composed of Alphaproteobacteria and Gammaproteobacteria. In the Red Sea, LNA are found in the upper epipelagic layer while HNA prokaryotes are in the mesopelagic layer. Heterotrophic bacteria plays a significant part in carbon cycling by turning the dissolved organic matter (DOM) into carbon dioxide. In coastal environments archaea picoplankton have been found to be the least diverse within the community.