Coccolithus pelagicus

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Classification

Domain; Phylum; Class; Order; family [Others may be used. Use NCBI link to find]

Species

NCBI: Taxonomy

Genus species

Description and Significance

Describe the appearance, habitat, etc. of the organism, and why you think it is important.

Coccolithus pelagicus is one of over 200 species of coccolithophore [X]. They are the most productive oceanic calcifiers in the world. Like other coccolithophores, Coccolithus pelagicus is a unicellular, eukaryotic phytoplankton that is characterized by distinctive calcite scales [X]. These calcite scales are known as coccoliths, which cover each individual cell like an exoskeleton. Research has shown that coccoliths are important for coccolithophores in the context of

C. pelagicus enjoys cold waters, specifically around 2-12 degrees Celsius [X]. It is usually found in subarctic oceans, with high prevalence in the northern Atlantic [X]. Concentrations can also be found near upwellings, or areas where wind drives denser, cooler water from ocean depths to the ocean surface [X].

Genome Structure

The genome of Coccolithus pelagicus has not yet been sequenced, and little is known about its genomic content. Emiliana huxleyi is another coccolithophore closely related to C. pelagicus that has a 167.7 Mb sequenced genome assumed to be similar to C. pelagicus. E. huxleyi has over 30,000 putative genes, with many of them providing functions related to carbon and calcium transport, as well as metabolism [X].

Cell Structure, Metabolism and Life Cycle

Interesting features of cell structure; how it gains energy; what important molecules it produces.

Ecology

Habitat

C. pelagicus is found in Arctic and Subarctic cold waters across the North Atlantic and North Pacific (Mcintyre and Bé, 1967) with a minimal temperature of -1.7°C and an optimal temperature of 8°C (Baumann et al, 2000). However, coccospheres from this species have been reported in the Mediterraean (Daniels, 2015) and in New Zealand (Nishida, 1979). It is a major calcite producer in its North Atlantic range despite being less abundant than other calcifiers such as E. huxleyi (Daniels, 2015). C. pelagicus rarely dominates the phytoplanktonic community and has relatively low abundance (Poulton et al, 2006, 2007) but blooms have been reported in shallow waters with concentrations up to 10⁶ cells per L (Milliman, 1980).

Biogeochemical relevance

Biological Carbon Pump

Phytoplankton are predominant contributors to Earth’s photosynthetic activity and form the base of the trophic network of marine ecosystems as primary producers. Photosynthesis and chemosynthesis are the major sources of all organic carbon on Earth. Through carbon fixation, phytoplankton have a critical impact on CO₂ concentration. Coccolithophores fix inorganic CO₂ into particulate organic carbon (POC) and thus have an impact on the PIC/POC ratio. As organic carbon flows to the deep ocean as particles, it is mainly remineralized before it reaches the depth of 1000 meters considered necessary for sequestration (Sanders et al, 2014).

Carbonate pump

There are three main components of dissolved inorganic carbon (DIC) in seawater: a carbon dioxide-carbonic acid pool (CO₂ + H₂CO₃) at equilibrium, carbonate (CO₃^2-) and bicarbonate (HCO₃^-).
In addition to carbon fixation through photosynthesis, clalcifiers such as C. pelagicus produce CaCO₃ shells that participate in fixing CO₂ into (PIC). The inorganic carbon cycle participates in reducing the DIC concentration at the surface of oceans (Falkowski et al, ) and is a major actor in the flow of particulate carbon to the deep ocean.
The PIC to POC ratio, driven by the rates of calcification and photosynthesis, determines whether calcifiers act as a source of CO₂, or a sink. The immediate consequence of calcification is a production of CO₂ resulting from the assimilation of bicarbonate (HCO₃^-) ions. However, over longer geological periods, the effects of calcification in ocean waters are of a carbon sink.

Ocean Acidification and Warming

Carbonate and bicarbonate account for a major control of the pH of seawater through the CO₂ to HCO₃^- and CO₃^2- equilibrium. Calcification rate experiments suggest that impacts of seawater acidification are species-specific (Gafar et al, 2019). Thus, the structure of phytoplanktonic communities is expected to change in an acidifying ocean.
Experimental approaches have showed that high seawater temperatures increase the requirements of micro-nutrients such as phosphorus (P) and decrease the PIC/POC ratio by 40-60% (Gerecht et al, 2014). Temperature-challenged cells grew more calcite plates malformations (Gerecht et al, 2014). Increased temperature experiments on calcification rates and growth have showed conflicting results and further research is needed to investigate the consequences of Ocean Warming on C. pelagicus.

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

[] McIntyre, A. and Bé, A. W. H. "Modern coccolithophoridae of the Atlantic Ocean—I. Placoliths and cyrtoliths". Deep Sea Research and Oceanographic Abstracts. 1967. Volume 14. p. 561-597.

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Author

Page authored by _____, student of Prof. Jay Lennon at IndianaUniversity.