Biogeochemical and ecological impact of Pacific islands

In the poor waters of the tropical Pacific, islands are sources of nutrients for microscopic photosynthetic algae, or phytoplankton, in the surrounding waters. This results in an enrichment of phytoplankton - a "bloom" - near the islands, which supports higher trophic levels, including the fish that are essential for the survival of the islanders. This fertilizing effect, known as the "island effect", results in an increase in chlorophyll concentration (an indicator of phytoplankton biomass) which can be identified by satellite observations of water color. The researchers developed an algorithm that automatically identifies the island-enriched area from a chlorophyll concentration map and applied it to a database of all Pacific islands. The algorithm detects seasonal enrichments for 99% of the islands, representing 3% of the tropical Pacific's surface area, while the islands represent only 0.4%. The researchers quantified local and basin-wide increases in chlorophyll and primary production by comparing island-enriched waters with neighboring waters. They also found, for the first time, significant impacts on phytoplankton community structure and biodiversity, visible in water color signal anomalies. These results suggest that in addition to strong local biogeochemical impacts, islands may have even greater ecological impacts.

For more information

Messié, M., Petrenko, A., Doglioli, A.M. et al. Basin-scale biogeochemical and ecological impacts of islands in the tropical Pacific Ocean. Nat. Geosci. (2022).

Contact

Monique Messié
MBARI
+1 831 775 1836
monique@mbari.org
Anne Petrenko
MIO/PYTHEAS
04 86 09 06 06
anne.petrenko@mio.osupytheas.fr