08 Jan 2021

08 Jan 2021

Review status: this preprint is currently under review for the journal BG.

Abundances and morphotypes of the coccolithophore Emiliania huxleyi in southern Patagonia compared to neighboring oceans and northern-hemisphere fjords

Francisco Díaz-Rosas1,2, Catharina Alves-de-Souza3, Emilio Alarcón4,5, Eduardo Menschel5,6, Humberto E. González5,6, Rodrigo Torres4,5, and Peter von Dassow1,2,7 Francisco Díaz-Rosas et al.
  • 1Facultad de Ciencias Biológicas, Departamento de Ecología, Pontificia Universidad Católica de Chile, Santiago, Chile
  • 2Instituto Milenio de Oceanografía de Chile, Concepción, Chile
  • 3Algal Resources Collection, Center for Marine Science, University of North Carolina Wilmington, Wilmington, USA
  • 4Centro de Investigación en Ecosistemas de la Patagonia, Coyhaique, Chile
  • 5Centro de Investigación Dinámica de Ecosistemas Marinos de Altas Latitudes, Punta Arenas, Chile
  • 6Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile
  • 7UMI 3614, Evolutionary Biology and Ecology of Algae, CNRS-UPMC Sorbonne Universités, PUCCh, UACH

Abstract. Coccolithophores are potentially affected by ongoing ocean acidification, where rising CO2 lowers seawater pH and calcite saturation state (Ωcal). Southern Patagonian fjords and channels provide natural laboratories for studying these issues due to high variability in physical and chemical conditions. We surveyed coccolithophore assemblages in Patagonian fjords during late-spring 2015 and early-spring 2017. Surface Ωcal exhibited large variations driven mostly by freshwater inputs. High Ωcal conditions (max. 3.6) occurred in the Archipelago Madre de Dios. Ωcal ranged from 2.0–2.6 in the western Strait of Magellan, 1.5–2.2 in the Inner Channel, and was sub-saturating (0.5) in Skyring Sound. Emiliania huxleyi was the only coccolithophore widely distributed in Patagonian fjords (> 96 % of total coccolitophores), only disappearing in the Skyring Sound, a semi-closed mesohaline system. Correspondence analysis associated higher E. huxleyi biomasses with lower diatom biomasses. The highest E. huxleyi abundances in Patagonia were in the lower range of those reported in Norwegian fjords. Predominant morphotypes were distinct from those previously documented in nearby oceans but similar to those of Norwegian fjords. Moderate-calcified forms of E. huxleyi A morphotype were uniformly distributed throughout Patagonia fjords. The exceptional R/hyper-calcified coccoliths, associated with low Ωcal values in Chilean and Peruvian coastal upwellings, were a minor component associated with high Ωcal levels in Patagonia. Outlying mean index (OMI) niche analysis suggested that pH/Ωcal conditions explained most variation in the realized niches of E. huxleyi morphotypes. The moderate-calcified A morphotype exhibited the widest niche-breadth (generalist), while the R/hyper-calcified morphotype exhibited a more restricted realized niche (specialist). Nevertheless, when considering an expanded sampling domain, including nearby Southeast Pacific coastal and offshore waters, even the R/hyper-calcified morphotype exhibited a higher niche breadth than other closely phylogenetically-related coccolithophore species. The occurrence of E. huxleyi in naturally low pH/Ωcal environments indicates that its ecological response is plastic and capable of adaptation.

Francisco Díaz-Rosas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2020-449', Anonymous Referee #1, 21 Feb 2021
  • RC2: 'Comment on bg-2020-449', Anonymous Referee #2, 27 Apr 2021
  • RC3: 'Comment on bg-2020-449', Mariem Saavedra, 09 May 2021

Francisco Díaz-Rosas et al.

Francisco Díaz-Rosas et al.


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Short summary
Coccolithophores are important unicellular algae with a calcium carbonate covering that might be affected by ongoing changes in the ocean due to absorption of CO2, warming, and melting of glaciers. We used the Southern Patagonian Fjords as a natural laboratory, where chemical conditions are naturally highly variable. One variant of a widespread coccolithophore species can tolerate these conditions, suggesting it is highly adaptable, while others were excluded, suggesting they are less adaptable.