Ocean Microbes Offer Potential Climate Solution, But Risks Remain

Researchers are investigating how microscopic marine plants—phytoplankton—could be harnessed to combat climate change, while also acknowledging potential ecological risks associated with large-scale interventions. These organisms play a vital role in Earth’s systems, responsible for roughly half of the carbon dioxide absorbed through photosynthesis globally and producing approximately 50% of atmospheric oxygen. Phytoplankton also form the base of marine food webs, supporting zooplankton populations that are then consumed by larger creatures like fish and crustaceans.

While proponents suggest that relatively small amounts of micronutrients, predominantly iron, could generate substantial biomass and offer a cost-effective solution, significant uncertainties persist. Concerns center on the potential for unintended ecological consequences. For instance, stimulating undesirable phytoplankton species like Pseudo-nitzschia, which produce the neurotoxin domoic acid—harmful to marine mammals and humans—is a possibility. Further complicating matters is the fact that zooplankton consume phytoplankton, meaning shifts in phytoplankton populations could ripple through the entire food chain. Zooplankton also contribute significantly to carbon sequestration by sinking carbon-rich fecal pellets to the ocean floor.

The process of phytoplankton fertilization can also affect ocean chemistry. The decomposition of vast blooms can deplete oxygen levels and create “dead zones,” where marine life struggles to survive, though this typically requires very large-scale fertilization. Researchers are now striving to determine the true amount of carbon dioxide that could be captured through these interventions; specifically, they need to ascertain how much is incorporated into diatoms, packaged within zooplankton fecal pellets, transported to the seafloor, and ultimately stored long-term.