Marine microorganisms

Role of the microbial community in the marine carbon cycle

Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism (or microbe) is any microscopic living organism or virus, which is invisibly small to the unaided human eye without magnification. Microorganisms are very diverse. They can be single-celled[1] or multicellular and include bacteria, archaea, viruses, and most protozoa, as well as some fungi, algae, and animals, such as rotifers and copepods. Many macroscopic animals and plants have microscopic juvenile stages. Some microbiologists also classify viruses as microorganisms, but others consider these as non-living.[2][3]

Marine microorganisms have been variously estimated to make up about 70%,[4] or about 90%,[5][6] of the biomass in the ocean. Taken together they form the marine microbiome. Over billions of years this microbiome has evolved many life styles and adaptations and come to participate in the global cycling of almost all chemical elements.[7] Microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers. They are also responsible for nearly all photosynthesis that occurs in the ocean, as well as the cycling of carbon, nitrogen, phosphorus and other nutrients and trace elements.[8] Marine microorganisms sequester large amounts of carbon and produce much of the world's oxygen.

A small proportion of marine microorganisms are pathogenic, causing disease and even death in marine plants and animals.[9] However marine microorganisms recycle the major chemical elements, both producing and consuming about half of all organic matter generated on the planet every year. As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system.

In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all life on the planet, including the marine microorganisms.[10] Despite its diversity, microscopic life in the oceans is still poorly understood. For example, the role of viruses in marine ecosystems has barely been explored even in the beginning of the 21st century.[11]

  1. ^ Madigan M; Martinko J, eds. (2006). Brock Biology of Microorganisms (13th ed.). Pearson Education. p. 1096. ISBN 978-0-321-73551-5.
  2. ^ Rybicki EP (1990). "The classification of organisms at the edge of life, or problems with virus systematics". South African Journal of Science. 86: 182–6. ISSN 0038-2353.
  3. ^ Lwoff A (1956). "The concept of virus". Journal of General Microbiology. 17 (2): 239–53. doi:10.1099/00221287-17-2-239. PMID 13481308.
  4. ^ Bar-On, YM; Phillips, R; Milo, R (2018). "The biomass distribution on Earth". PNAS. 115 (25): 6506–6511. Bibcode:2018PNAS..115.6506B. doi:10.1073/pnas.1711842115. PMC 6016768. PMID 29784790.
  5. ^ Census Of Marine Life Accessed 29 October 2020.
  6. ^ Cavicchioli, Ricardo; Ripple, William J.; Timmis, Kenneth N.; Azam, Farooq; et al. (2019). "Scientists' warning to humanity: Microorganisms and climate change". Nature Reviews Microbiology. 17 (9): 569–586. doi:10.1038/s41579-019-0222-5. PMC 7136171. PMID 31213707. Modified text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  7. ^ Bolhuis, H. and Cretoiu, M.S. (2016) "What is so special about marine microorganisms?". In: L. J. Stal and M. S. Cretoiu (Eds.) The Marine Microbiome, pages 3–20, Springer. ISBN 9783319330006
  8. ^ "Functions of global ocean microbiome key to understanding environmental changes". www.sciencedaily.com. University of Georgia. 10 December 2015. Retrieved 11 December 2015.
  9. ^ 2002 WHO mortality data Accessed 20 January 2007
  10. ^ Wade, Nicholas (25 July 2016). "Meet Luca, the Ancestor of All Living Things". New York Times. Retrieved 25 July 2016.
  11. ^ Suttle CA (2005). "Viruses in the Sea". Nature. 437 (9): 356–361. Bibcode:2005Natur.437..356S. doi:10.1038/nature04160. PMID 16163346. S2CID 4370363.