Wed Sep 25 09:00:01 UTC 2024: ## Invisible Forest Thriving in Warming Ocean: Subsurface Phytoplankton Flourish While Surface Levels Remain Stable

**Exeter, UK** – New research from the University of Exeter reveals a hidden world beneath the ocean surface where phytoplankton are thriving in response to warming temperatures. While surface phytoplankton, the primary food source for many marine creatures, show signs of stress, their counterparts in the subsurface are experiencing a boom in biomass.

This discovery, published in the journal Nature Climate Change, challenges the current understanding of how phytoplankton respond to climate change. Researchers, using 33 years of data from the Bermuda Atlantic Time-series Study (BATS), found that the depth of the surface mixed-layer (where turbulent ocean currents occur) has decreased as the ocean rapidly warms. This shift has led to a reduction in chlorophyll levels in surface phytoplankton, but surprisingly, their overall biomass has remained steady.

However, the subsurface phytoplankton, residing in the low-light conditions below the surface, have experienced an increase in biomass over the last decade. This indicates a fundamental shift in the vertical structure of phytoplankton communities in response to warming.

“Our findings reveal that deep-living phytoplankton respond differently to ocean warming and climate variability compared to surface phytoplankton,” said Dr. Johannes Viljoen, lead author of the study. “This highlights the limitations of relying solely on satellite observations, which cannot see below the surface, and underscores the urgent need for improved global monitoring of phytoplankton in this hidden realm.”

The implications of this discovery are significant, as phytoplankton play a vital role in the marine food web and the global carbon cycle. Changes in their population could have cascading effects on marine ecosystems and climate change.

“Continued monitoring of these deep-living phytoplankton will help scientists better understand ongoing changes in the ocean that might otherwise go unnoticed,” added Dr. Viljoen. This research emphasizes the importance of exploring the unseen depths of the ocean to fully comprehend the impacts of climate change on our planet.

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