The Role of Phytoplankton in a Changing Planet

The Ribalet Lab is a biological oceanography group at the University of Washington. We study phytoplankton, microscopic organisms that fuel ocean food webs and regulate Earth’s carbon cycling. Using SeaFlow, our custom-built flow cytometer, we track these cells in real time during research cruises, collecting data every kilometer across the global ocean. By combining these measurements with statistical models, we show how environmental changes shape phytoplankton growth and community dynamics, and how these tiny organisms help regulate the health of marine ecosystems and the planet’s climate.


High-Resolution Ocean Observations
High-Resolution Ocean Observations

We use our custom-built SeaFlow flow cytometer to collect continuous, real-time observations of phytoplankton at sea. The instrument measures the size and fluorescence of individual cells every kilometer, capturing the fine-scale ecosystem structure that underlies larger patterns in ocean productivity and carbon cycling. Over the last decade, this automated system has analyzed more than 800 billion cells during nearly six global circumnavigations, revealing rapid shifts and small-scale processes that shape ecosystem dynamics across ocean basins.

Statistical Tools and Population Models
Statistical Tools and Population Models

We use statistical models to extract biological insights from SeaFlow data. We develop population models to estimate key rates - such as growth, division and mortality - from the spatial and temporal changes in phytoplankton size distributions. By linking these rates to environmental conditions, we show how factors like temperature, nutrients, and light shape phytoplankton communities on a global scale.