Ecological imperatives for aquatic CO2-concentrating mechanisms

Area of Science:

• Aquatic Botany
• Biogeochemistry
• Physiological Ecology

Background:

• Inorganic carbon availability in aquatic environments is highly variable, often limiting for photosynthesis.
• CO2 diffusion is slow in water, making inorganic carbon more limiting than in terrestrial ecosystems.
• CO2-concentrating mechanisms (CCMs) are common in aquatic photoautotrophs to overcome carbon limitation.

Purpose of the Study:

• To review the diversity and ecological relevance of CCMs in aquatic photoautotrophs.
• To understand the environmental factors influencing the regulation and distribution of CCMs.
• To highlight understudied areas in CCM research, particularly in marine systems.

Main Methods:

• Literature synthesis and review of existing research on aquatic CCMs.
• Analysis of environmental factors (e.g., CO2, pH, light) affecting CCM activity.
• Comparison of CCM strategies across different aquatic taxa and environments.

Main Results:

• CCMs are widespread in aquatic photoautotrophs, with biochemical or biophysical strategies to acquire inorganic carbon.
• CCM activity is regulated by environmental conditions, being favored in low CO2, high HCO3-, high pH, and high light.
• Freshwater species exhibit a wider range of carbon acquisition abilities compared to marine species, reflecting environmental variability.

Conclusions:

• CCMs are critical for aquatic primary productivity, with their prevalence and type shaped by ecological and environmental factors.
• Further research on CCMs in seagrasses, marine phytoplankton, and larger aquatic photoautotrophs is needed.
• Integrating ecological context with mechanistic studies will enhance understanding of CCMs' role in aquatic ecosystem function.