Diatoms are the most important producers of plant biomass in the ocean and help to transport carbon dioxide (CO2) from the atmosphere into the deep ocean and thus regulate our climate.
Diatoms are the most important producers of plant biomass in the ocean and help to transport carbon dioxide (CO2) from the atmosphere into the deep ocean and thus regulate our climate. Because diatoms rely on silica rather than calcium carbonate to build their shells, they were previously thought to benefit from ocean acidification – a chemical change in seawater triggered by the increasing uptake of CO2 that makes calcification more difficult. In a study published today in Nature, scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel show that diatoms, which are a type of plankton, are also affected. Analyses of data from field experiments and model simulations suggest that ocean acidification could drastically reduce diatom populations.
While calcifying organisms like oysters and corals have difficulty forming their shells and skeletons in more acidic seawater, diatoms have been considered less susceptible to the effects of ocean acidification – a chemical change triggered by the uptake of carbon dioxide (CO2). The globally widespread tiny diatoms use silica, a compound of silicon, oxygen and hydrogen, as a building material for their shells. That diatoms are nevertheless under threat has now been demonstrated for the first time by researchers from GEOMAR Helmholtz Centre for Ocean Research Kiel, the Institute of Geological and Nuclear Sciences Limited New Zealand and the University of Tasmania in a study published in Nature. For the study, researchers linked an overarching analysis of various data sources with Earth system modeling. The findings provide a new assessment of the global impact of ocean acidification.
As a result of ocean acidification, the silicon shells of diatoms dissolve more slowly. This is not an advantage – it causes diatoms to sink into deeper water layers, before they chemically dissolve and are converted back into silica. Consequently, this nutrient is more efficiently exported to the deep ocean and thus becomes scarcer in the light-flooded surface layer, where it is needed to form new shells. This causes a decline in diatoms, according to the scientists in their recent publication. Diatoms contribute 40 percent of the production of plant biomass in the ocean and are the basis of many marine food webs. They are also the main driver of the biological carbon pump that transports CO2 into the deep ocean for long-term storage.
Read more at Helmholtz Centre for Ocean Research Kiel (GEOMAR)
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