Helicosphaera carteri (Prymnesiophyceae) under high carbon dioxide: An experimental study

Area of Science:

• Marine biology
• Biogeochemistry
• Oceanography

Background:

• Coccolithophores like Helicosphaera carteri are vital marine calcifiers impacting ecosystems and carbon cycling.
• Understanding their response to ocean acidification is crucial for predicting future ocean health.

Purpose of the Study:

• To investigate the impact of varying carbon dioxide (CO2) levels on the growth rate and carbon production of Helicosphaera carteri.
• To assess the sensitivity of H. carteri to ocean acidification and validate methods for carbon production measurement.

Main Methods:

• Utilized dilute batch cultures with manipulated CO2 concentrations (295, 444, and 600 μatm).
• Measured key eco-physiological parameters: growth rate and particulate carbon production (both organic and inorganic).
• Validated the assumption of constant particulate carbon quotas in dilute batch cultures.

Main Results:

• Helicosphaera carteri growth and organic carbon production were limited by CO2 at 295 μatm.
• Neither growth nor carbon production was inhibited at 600 μatm CO2, indicating low sensitivity to acidification.
• Inorganic carbon production remained stable, and the assumption of constant particulate carbon quotas was validated.

Conclusions:

• Helicosphaera carteri demonstrates a lower sensitivity to ocean acidification compared to other coccolithophores.
• The findings support the reliability of current methods for measuring carbon production in marine calcifiers.
• This resilience has significant implications for marine ecosystem function and the global carbon cycle under future climate scenarios.