Process of unveiling the foundations of ocean ecosystems

Phytoplankton are the basis of ocean ecosystems: like tropical forests, they consume carbon from the atmosphere, form the basis of the aquatic food web, and play a critical role in the impact of fish abundance and the global climate. .

Understanding how these microscopic organisms develop is essential in determining how much fish is available to harvest and how the climate will continue to change. However, incomplete knowledge of how phytoplankton respond to change hampers our ability to predict how it will be affected by climate change.

Researchers at the University of Liverpool, Dalhousie University, GEOMAR in Kiel and the Scripps Institution of Oceanography have developed a new mechanistic framework to examine the growth of phytoplankton in the ocean.

The growth of phytoplankton can be thought of as a factory: the materials enter the factory and are processed on assembly lines, forming the final product. For phytoplankton, this product grows faster and they rearrange their “cell assembly chains” to grow rapidly.

Traditionally, it has been fine that the scarcest seawater resource determines the growth of phytoplankton, but this overlooks an emerging biochemical understanding of cell physiology.

Led by Scott McCain, a doctoral student in the Department of Biology at Dalhousie, the team focused specifically on the costs of these “cell assembly chains” associated with the various resources that go into making phytoplankton, rather than the quantity. of materials available. They then built a mathematical model of a phytoplankton to represent these costs, uncovering new explanations for different phytoplankton behaviors.

Professor Alessandro Tagliabue, Department of Earth, Ocean and Ecology Sciences, University of Liverpool, said: “You can think of the cell as a mini-economy, we have to look at the sum of all the internal costs of growth in a given environment to predict the ultimate growth rate.

This fundamentally changes the way we view phytoplankton growth and will lead to better predictions of how much phytoplankton grows in the ocean, and therefore will also impact our predictions for fisheries and global climate change. It is important to note that this model could only have been informed by a range of biochemical data which are generally not taken into account in these types of models.

Prof Tagliabue said: This work “advances a whole new paradigm by focusing on what is happening inside the cell, rather than in seawater, which was the previous goal” . In doing so, our new approach brings together theory and observations like never before and offers an exciting future for better models. “

Ultimately, this new understanding can be used to inform larger-scale models and reduce uncertainty about how warming oceans will affect key ocean ecosystem services such as net primary production, sequestration of the ocean. carbon and support for the marine food supply.

The article “Cellular Costs Underlying Micronutrient Limitation in Phytoplankton” (doi: 10.1126 / sciadv.abg6501) is published in the journal Scentce Advances.

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