An ‘invisible forest’ of algae is spreading across the warming ocean

September 25 () –

A new study shows that an ‘invisible forest’ of phytoplankton is thriving in parts of the warming oceans.

Phytoplankton are tiny organisms that float adrift and perform approximately half of the “primary production” of the planet (the formation of living cells through photosynthesis).

The new study, conducted by the University of Exeter, examined phytoplankton at the ocean surface and in the “subsurface” (a distinct layer of water below) to see how climate variability is affecting them.

Published in the magazine Nature Climate Changethe findings show that these two communities are reacting differently.

Over the past decade, the total “biomass” (living matter) of subsurface phytoplankton has increased in response to warming.

Meanwhile, surface phytoplankton now has less chlorophyll, making it less green, but in fact the total biomass has remained stable.

Based on 33 years of data from the Bermuda Atlantic Time Series Study (BATS) in the Sargasso Seathe findings also suggest that the depth of the “surface mixed layer” (region of turbulence at the ocean surface) has become lower as the ocean has warmed rapidly over the past decade.

“It is important to understand these trends because phytoplankton are the foundation of the marine food web and play a key role in removing carbon dioxide from the atmosphere,” he said. in a statement Dr Johannes Viljoen, from the Department of Earth and Environmental Sciences at Exeter’s Penryn Campus in Cornwall.

“Our findings reveal that deep-living phytoplankton, which thrive in low-light conditions, respond differently to ocean warming and climate variability compared to surface phytoplankton. We typically rely on satellite observations to monitor phytoplankton, but the subsoil is hidden from satellite view.

“Our study highlights the limitations of satellite observations and underscores the urgent need to improve global monitoring of phytoplankton below what satellites can see.”

Co-author Dr Bob Brewin added: “Changes at the base of the food web can have cascading effects on marine life, from tiny zooplankton to large fish and marine mammals.

“Therefore, the future of phytoplankton will have important implications for biodiversity as well as climate change.”

Dr Viljoen added: “Continuous monitoring of these deep-living phytoplankton will help scientists better understand ongoing changes in the ocean that might otherwise go unnoticed.”