Underwater algae all evolved CO2 pumps to survive
Iñiguez C, Capó-Bauçà S, Gordillo FJL, Cobos P, Aguiló-Nicolau P
Climate Adaptation
The green scum on a pond and the diatoms drifting through a lake are running a completely different carbon-capture strategy than the plants in your yard, and understanding it helps scientists predict how aquatic ecosystems will respond as CO2 and ocean temperatures keep rising.
Plants that live underwater, like algae and diatoms, face a tough problem: CO2 moves through water far slower than through air, so their carbon-fixing enzyme (Rubisco) never gets enough gas on its own. To cope, nearly every aquatic photosynthesizer evolved some kind of internal pump or concentrating structure that boosts CO2 levels around Rubisco. This study compares those pumps across many species and finds they all took a different evolutionary path than land plants did.
Key Findings
None of the surveyed aquatic species can achieve CO2-saturated photosynthesis through Rubisco kinetics alone; all depend on CO2-concentrating mechanisms (CCMs)
CCM effectiveness (Kcair/Km CO2 ratio) is consistently higher in organisms with Rubisco-containing microcompartments like pyrenoids and carboxysomes, though pyrenoids aren't strictly necessary for concentrating CO2 above ambient levels
An inverse relationship between Rubisco carboxylation efficiency and CO2 affinity reveals aquatic organisms followed a different CCM-Rubisco coevolutionary path than terrestrial plants, likely shaped by oxygen buildup in submerged conditions
chevron_right Technical Summary
Algae, cyanobacteria, diatoms, and other water-dwelling photosynthesizers all rely on internal CO2-pumping systems to fix carbon efficiently, since none of them can get enough CO2 through their basic enzyme machinery alone. This research maps how different aquatic organisms evolved distinct solutions to the same problem: water makes it hard to get CO2 to the cellular engine that builds sugar from sunlight.
Abstract Preview
Original paper
Rubisco kinetic diversity and effectiveness of CO2-concentrating mechanisms in aquatic photosynthetic organisms.
Aquatic photoautotrophs experience strong physicochemical constraints on inorganic carbon acquisition due to low CO2 and O2 diffusion in water producing a strong reduction in the gas conductance. T...
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A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's biomass. They generate about 20 to 50 percent of the oxygen produced on the planet ea...