Effect of sulfate availability on phytoplankton stoichiometry

Area of Science:

• Marine biology
• Biogeochemistry
• Phytoplankton physiology

Background:

• Sulfur (S) is crucial for phytoplankton metabolism.
• Limited research exists on S availability's effect on phytoplankton elemental composition.
• Previous studies yielded contradictory results on S quotas.

Purpose of the Study:

• To investigate the impact of sulfate availability on elemental quotas and stoichiometry in marine phytoplankton.
• To compare S quotas between different phytoplankton lineages under varying sulfate conditions.
• To explore physiological responses to sulfate fluctuations.

Main Methods:

• Cultured 20 marine phytoplankton species under different sulfate concentrations.
• Measured elemental concentrations using high-temperature combustion oxidation and X-ray fluorescence.
• Analyzed carbon (C):S and S:P ratios.

Main Results:

• Red lineage phytoplankton exhibited higher S quotas than green lineage, irrespective of sulfate levels.
• Red lineage showed lower C:S (93) and higher S:P (1.06) ratios compared to green lineage (226 and 0.76).
• Phytoplankton physiologically adjusted by altering phosphorus or zinc quotas in response to sulfate availability.

Conclusions:

• Phytoplankton S quotas are likely under genetic control, favoring the red lineage.
• These genetic constraints on S quotas support the sulfate facilitation hypothesis.
• Physiological adjustments in P and Zn quotas demonstrate cellular adaptation to environmental sulfate levels.