While I may have felt like a stranger to the ocean, my lungs knew otherwise. It is estimated that half of the oxygen we breathe comes from microscopic life of the sea: phytoplankton. These single-celled, photosynthetic drifters form the foundation of ocean ecosystems and link the ocean to the atmosphere. Among them are diatoms, which stand out as one of the most important and diverse groups. Under the microscope, these organisms display intricate cylindrical forms with transparent walls of opaline silica. The walls, called frustules, are porous and etched with delicate, honeycomb-like patterns. Inside, chloroplasts power photosynthesis, fueling the oxygen we breathe each day.
Image by Shelley P. Russell
Through photosynthesis, phytoplankton transform carbon dioxide and sunlight into organic matter, forming the foundation of marine food webs. They are grazed by zooplankton, which in turn sustain larger organisms such as fish, whales, and seabirds. A single teaspoon of seawater can hold thousands to nearly a million phytoplankton cells, a pulse of life unimaginable in my landlocked summers. This hidden vitality drives nearly half of Earth’s primary production, capturing some 50 gigatons of carbon dioxide each year. By capturing half of the planet’s CO2, phytoplankton drive the biological carbon pump, quietly regulating climate and biogeochemical cycles.
Adding to their remarkable capabilities, phytoplankton boast diversity, large population sizes, and rapid division rates, enabling them to adapt quickly to changing environmental conditions. In an era of ocean warming, acidification, and dwindling nutrients, we can only hope their resilience holds, but it remains a high-stakes gamble. Findings suggest that environmental stressors are already affecting their physiology, community dynamics, and role in carbon cycling. While phytoplankton are just one part of a vast and complex system, they remind us that even the smallest organisms can exert immense ecological influence. Their resilience is remarkable but not limitless. To me, they are a quiet reminder that what is unseen is often profound; threads that fill our lungs and anchor the planet’s delicate harmony.
Today, I am grateful to have the ebbs and tides at my doorstep. Moving to the coast felt less like relocation than reunion, as if the ocean had been waiting all along. Studying it only deepened that bond, and I eventually came to meet some of the ocean’s greatest storytellers, not only through Cousteau, Carson, and Attenborough, but also in the species themselves, like the drifting brilliance of phytoplankton, whose quiet persistence makes all else possible.
Shelley Pearl Russell
Further reading & References
- Basu, S., & Mackey, K. R. M. (2018). Phytoplankton as Key Mediators of the Biological Carbon Pump: Their Responses to a Changing Climate. Sustainability, 10(3), 869. https://doi.org/10.3390/su10030869
- Caldeira, K., & Wickett, M. E. (2003). Oceanography: anthropogenic carbon and ocean pH. Nature, 425(6956), 365. https://doi.org/10.1038/425365a
- Falkowski, P. G., Barber, R. T., & Smetacek, V., V (1998). Biogeochemical Controls and Feedbacks on Ocean Primary Production. Science (New York, N.Y.), 281(5374), 200–207. https://doi.org/10.1126/science.281.5374.200
- Field, C. B., Behrenfeld, M. J., Randerson, J. T., & Falkowski, P. (1998). Primary production of the biosphere: integrating terrestrial and oceanic components. Science (New York, N.Y.), 281(5374), 237–240. https://doi.org/10.1126/science.281.5374.237
- Henson, S. A., Cael, B. B., Allen, S. R., & Dutkiewicz, S. (2021). Future phytoplankton diversity in a changing climate. Nature communications, 12(1), 5372. https://doi.org/10.1038/s41467-021-25699-w
