Phytoplankton: The Lungs of the Earth

Why It Matters

Phytoplankton underpin a quarter of global carbon removal; their decline would weaken a key climate buffer, raising stakes for emissions reductions and ocean‑management policies.

Key Takeaways

• Phytoplankton fix about 40% of atmospheric CO₂ annually.
• Ocean warming increases stratification, limiting nutrient supply to surface phytoplankton.
• Smaller phytoplankton species thrive under nutrient scarcity, storing less carbon.
• Experiments add nutrients to study genetic responses and community shifts.
• Declining phytoplankton carbon uptake could accelerate climate‑change feedback loops.

Summary

Marine biogeochemist Arianwen Herbert explains how microscopic phytoplankton act as the ocean’s lungs, fixing roughly 40% of atmospheric carbon dioxide. Aboard the RRS James Cook she compares their role to tropical rainforests and sets the stage for a series of night‑time experiments.

The expedition shows that warming oceans become more stratified, cutting off nutrients to surface waters. This favors smaller phytoplankton species that store less carbon, creating a positive feedback loop that could amplify global warming.

Her team enriches samples with nutrients, incubates them for a week, and uses genetic sequencing to track which species dominate and which genes switch on. The “green flash” analogy underscores the hidden, vibrant world beneath the waves.

Understanding how phytoplankton communities will respond to climate change is crucial for refining carbon‑cycle models and informing mitigation strategies, as their decline could undermine a major natural carbon sink.

Original Description

You may have heard rainforests described as the 'lungs of the Earth', but what about the oceans? On the face of it, these environments couldn't seem more different. But actually, dive beneath the waves and you'll find a plethora of carbon-fixing heroes. Join biogeochemist and climate scientist Arianwen Herbert as she takes us behind-the-scenes on her fieldwork expedition aboard RRS James Cook, and introduces us to the amazing world of phytoplankton. Find out more at www.arianwen.com or follow her on Instagram@scienceformymum.