Ocean urea fertilization for carbon credits poses high ecological risks

Area of Science:

• Marine Biology
• Oceanography
• Environmental Science

Background:

• The Sulu Sea is a biodiverse marine region.
• Ocean fertilization is proposed to stimulate algal blooms for carbon sequestration.
• Urea is considered as a potential fertilizer.

Purpose of the Study:

• To evaluate the feasibility and potential consequences of using urea for ocean fertilization in the Sulu Sea.
• To assess the risks associated with stimulating algal blooms using urea, specifically concerning carbon sequestration and ecosystem impacts.

Main Methods:

• Analysis of urea's preferential uptake by specific phytoplankton groups (cyanobacteria, dinoflagellates).
• Evaluation of the efficiency of biological carbon pumps in deep-sea sequestration.
• Assessment of the potential for toxic algal bloom formation and subsequent ecological effects.
• Consideration of the energy costs and carbon footprint of urea production.

Main Results:

• Urea favors the growth of buoyant cyanobacteria and dinoflagellates, potentially limiting efficient carbon export.
• The biological carbon pump is inefficient, questioning net atmospheric carbon loss.
• High potential for toxic dinoflagellate blooms, some increasing toxicity with urea.
• Toxic dinoflagellate cysts can persist, leading to recurrent blooms.
• Decomposition of large blooms may cause hypoxia in bottom waters.
• Urea production is energy-intensive, relying on fossil fuels, thus limiting net carbon sequestration.

Conclusions:

• The proposed urea fertilization plan for the Sulu Sea is scientifically flawed.
• Significant risks include toxic blooms, hypoxia, and limited carbon sequestration efficacy.
• Potential adverse environmental and economic impacts necessitate rigorous assessment before any implementation.