Ocean acidification alters the nutritional value of Antarctic diatoms

The process of continuous acidification of oceanic waters undoubtedly leads to effects on several organisms

by Lorenzo Ciotti
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Ocean acidification alters the nutritional value of Antarctic diatoms

About a quarter of the CO2 present in the atmosphere ends up in the oceans where, in contact with water, it is transformed into carbonic acid. As CO2 in the atmosphere increases, there is also an increase in that dissolved in sea water; therefore the increase in CO2 emissions determines devastating effects on marine ecosystems.

In particular, according to the Intergovernmental Panel on Climate Change, from 1750 to 2014, a percentage equal to 30% of the CO2 emitted as a result of human activities was absorbed by the oceans. It has been estimated that between 1751 and 1994, the surface pH of ocean waters dropped from 8.25 to 8.14, with a corresponding increase in the concentration of H + ions, equal to 26%.

The process of continuous acidification of oceanic waters undoubtedly leads to effects on several organisms and on the food chain and, in particular, can affect the lysocline and the compensation depth of the carbonates; resulting in the dissolution of the calcareous shells of shells, molluscs and calcareous plankton, consisting of calcium carbonate (CaCO3).

The Ocean acidification study alters the nutritional value of Antarctic diatoms, published on the The New phytologist, said: "Primary production in the Southern Ocean is dominated by diatom-rich phytoplankton assemblages, whose individual physiological characteristics and community composition are strongly shaped by the environment, yet knowledge on how diatoms allocated cellular energy in response to ocean acidification (OA) is limited.

Understanding such changes in allocation is integral to determining the nutritional quality of diatoms and the subsequent impacts on the trophic transfer of energy and nutrients. Using synchrotron-based Fourier transform infrared microspectroscopy, we analyzed the macromolecular content of selected individual diatom taxa from a natural Antarctic phytoplankton community exposed to a gradient of fCO2 levels.

Strong species-specific differences in macromolecular partitioning were observed under OA. Large taxa showed preferential energy allocation towards proteins, while smaller taxa increased both lipid and protein stores at high fCO2.

If these changes are representative of fut ure Antarctic diatom physiology, we may expect a shift away from lipid-rich large diatoms towards a community dominated by smaller taxa, but with higher lipid and protein stores than their present-day contemporaries, a response that could have cascading effects on food web dynamics in the Antarctic marine ecosystem."