Photosynthetic CO₂ uptake by Ulva (Chlorophyta) as a potential contribution to global warming containment

The ongoing climate changes have resulted from high levels of anthropogenic CO₂ being released into the atmosphere in the past decades. Carbon-cutting measures have been proposed to reduce global warming by 2 °C, bringing it back to preindustrial levels. There are several options on hand to meet the need for carbon reduction on a global basis, and one such option refers to CO₂ sequestration via the photosynthesis of macroalgae. Species of the green seaweed Ulva are ubiquitous throughout the world oceans; they can maintain fast growth during most seasons thanks to their unique photosynthetic capacity combined with high nitrogen and phosphorous uptake rates. High commodity productions of seaweeds, such as green species of Ulva, can also deliver important additional benefits and ecosystem services, including human food, animal feed, proteins, minerals, or active natural molecules, therefore alleviating human needs shortly. Still, whether seaweeds, in general, can trap CO₂ for long periods (100 years) is controversial. Technical and biological gaps need to be resolved before an effective and sustainable seaweed-based mass production intended for the sequestration of CO₂ is established. This study elaborates on the potential global use of seaweeds in sequestering carbon and addresses the efficient inorganic carbon uptake and fixation traits of Ulva species. This study also overviews the photosynthetic traits and growth of seaweeds in offshore, semi-controlled, and land-based cultivation settings, focusing on total carbon budgets and footprints for Ulva sp. from the Israeli Mediterranean Sea. Altogether this work addresses the potential use of Ulva sp. as a valuable tool to moderate climate changes.