The Ocean is Home to Every Kind of Life
The ocean, covering over 70% of Earth's surface, is a vast and dynamic ecosystem teeming with a diverse array of life forms. From minute microorganisms to colossal blue whales, marine environments are bustling with a variety of taxa that represent nearly every major group of living organisms. The way biomass is distributed across these oceanic life forms underscores the ecological complexity of marine biomes, highlighting the critical roles different organisms play in sustaining oceanic health and productivity. This article will explore the various life forms that thrive in the ocean, their contributions to marine ecosystems, and their significance in maintaining the balance of this vast underwater world.[^1]
Microbial Life: The Foundation of Marine Ecosystems
Microbes form the foundation of marine ecosystems, contributing massively to the biomass within the oceans. Approximately 30% of the total marine biomass is composed of bacteria. Key bacterial groups include cyanobacteria like Prochlorococcus and Synechococcus, which are fundamental to the ocean's primary production and iron cycling.
Archaea, another vital microbial group, constitute about 10% of the marine biomass. Though less studied than bacteria, archaea play essential roles in nutrient cycles, including nitrogen fixation and methane oxidation. Additionally, protists, a diverse category that includes diatoms, dinoflagellates, and coccolithophores, represent around 20% of the marine biomass. These microorganisms are instrumental in primary production, forming the base of marine food webs. [^2]
Animal Life: From Crustaceans to Fish
In addition to microbes, various animals contribute significantly to the marine biomass. Crustaceans, including copepods, shrimp, and krill, make up around 15% of the ocean's biomass. These creatures are crucial for nutrient cycling and serve as primary food sources for many marine species.
Similarly, fish account for another 15% of the marine biomass, with small mesopelagic species like lanternfish forming a substantial part of this group. These fish are critical in the ocean's food webs, transferring energy from lower to higher trophic levels and contributing to carbon cycling through their vertical migrations and predation. [^1] [^3] [^4]
Plants and Algae: Primary Producers
Plants and algae, primarily in the form of phytoplankton and macroalgae, play pivotal roles in marine ecosystems. Phytoplankton, which are microscopic plants, drive primary production in the oceans and constitute about 1% of the marine biomass. These organisms convert sunlight into energy through photosynthesis, forming the foundation of most marine food webs.
Macroalgae, which include large seaweeds like kelp, represent less than 1% of the total marine biomass. Despite their smaller contribution, these organisms are vital in certain coastal ecosystems, providing habitat and food for various marine species.[^1][^3]
Other Significant Marine Life Forms
Viruses, although tiny and often overlooked, are abundant in marine environments and play critical roles in nutrient recycling.[^5][^6][^7] Despite their vast numbers, they only account for about 1% of the marine biomass. The lysis of bacterial cells by viruses releases nutrients back into the ecosystem, maintaining the balance of microbial communities.
Fungi, which represent less than 1% of the marine biomass, are found in diverse marine habitats, from the deep ocean to coastal regions like mangroves and estuaries.[^8][^9] These organisms contribute to the decomposition of organic matter and nutrient cycling, underlining their ecological importance despite their relatively small biomass.
Sources
[^1] Geosciences LibreTexts. (n.d.). 3.2: Biomass of organisms living in the oceans - Geosciences LibreTexts. LibreTexts. https://geo.libretexts.org/Learning_Objects/Distribution_of_Biomass_on_the_Planet/03%3A_Distribution_of_biomass_across_biotopes_and_trophic_modes/3.02%3A_Biomass_of_organisms_living_in_the_oceans (Accessed on 08/15/2024)
[^2] Whitman, W. B., Coleman, D. C., & Wiebe, W. J. (1998). Prokaryotes: The unseen majority. Proceedings of the National Academy of Sciences, 95(12), 6578-6583.
[^3] Joyard, J. (2023, April 28). Distribution of biomass on the planet. Encyclopedia of the Environment. https://www.encyclopedie-environnement.org/en/life/distribution-biomass-planet/ (Accessed on 08/15/2024)
[^4] Bar-On, Y. M., Phillips, R., & Milo, R. (2018). The biomass distribution on Earth. Proceedings of the National Academy of Sciences, 115(25), 6506-6511.
[^5] Middelboe, M., & Brussaard, C P D. (2017, October 18). Marine Viruses: Key Players in Marine Ecosystems. Multidisciplinary Digital Publishing Institute, 9(10), 302-302. https://doi.org/10.3390/v9100302
[^6] Suttle, C A. (2005, September 1). Viruses in the sea. Nature Portfolio, 437(7057), 356-361. https://doi.org/10.1038/nature04160
[^7] Weynberg, K D. (2018, January 1). Viruses in Marine Ecosystems: From Open Waters to Coral Reefs. Elsevier BV, 1-38. https://doi.org/10.1016/bs.aivir.2018.02.001
[^8] Amend, A S., Burgaud, G., Cunliffe, M., Edgcomb, V P., Ettinger, C L., Gutiérrez, M H., Heitman, J., Hom, E., Ianiri, G., Ishida, K., Kagami, M., Picard, K T., Quandt, C A., Raghukumar, S., Riquelme, M., Stajich, J., Vargas-Muñiz, J M., Walker, A K., Yarden, O., & Gladfelter, A S. (2019, April 30). Fungi in the Marine Environment: Open Questions and Unsolved Problems. American Society for Microbiology, 10(2). https://doi.org/10.1128/mbio.01189-18
[^9] Gladfelter, A S., James, T Y., & Amend, A S. (2023, February 6). Marine fungi. https://www.cell.com/current-biology/fulltext/S0960-9822(19)30148-4