Dust sparks rare massive phytoplankton bloom off Madagascar

Dust sparks rare massive phytoplankton bloom off Madagascar
by Erica Marchand
Paris, France (SPX) Oct 03, 2024

Recent research has revealed that dust carried from southern Africa towards Madagascar by wind triggered the largest phytoplankton bloom observed in two decades. This event, which occurred between November 2019 and January 2020, was particularly unusual due to its timing, as phytoplankton blooms are rarely seen during that time of year.

Dust clouds, transported over vast distances, are known to deposit essential nutrients when they settle on land or in the ocean. These nutrients can stimulate plant growth and boost marine productivity, including the growth of phytoplankton. The dust for this bloom originated in southern Africa and contributed to a bloom extending from the continent past Madagascar into the open Indian Ocean.

The relationship between desertification, dust emissions, and ocean fertilization is still not fully understood. However, the recent study published in 'PNAS Nexus' provides new insights into this connection. The research, conducted under ESA's Living Planet Fellowships Poseidon and Pyroplankton, demonstrated how rainborne dust deposition in the nutrient-poor waters southeast of Madagascar triggered the bloom.

John Gittings, the lead author of the study from the University of Athens, highlighted the use of multiple satellite datasets to track the bloom. "In addition to satellite data from the ESA Climate Change Initiative Ocean Colour project, we utilised information from ESA's Climate Change Initiative Soil Moisture project and ESA's Science for Society Biological Pump and Carbon Exchange Processes project. We also incorporated satellite data from the Copernicus Atmosphere Monitoring Service and the Copernicus Marine Service," said Dr. Gittings. This extensive data allowed the researchers to accurately trace the bloom's extent and identify the dust events that caused it.

Gittings added that the increase in air temperatures, aridity, and dust emissions in southern Africa could lead to more frequent occurrences of such blooms in the future, potentially linked to climate change.

Marie-Helene Rio from ESA emphasized the importance of studying ocean changes due to climate impacts, saying, "Oceans cover two-thirds of our planet and are vital to the health of our ecosystems. Understanding how climate change is altering their biological processes is not just a matter of scientific inquiry, it's crucial for life on Earth."

Research Report:An exceptional phytoplankton bloom in the southeast Madagascar Sea driven by African dust deposition