Carbon Dioxide (CO2) has had an unexpectedly harmful effect on crucial plankton populations. While calcifying organisms such as oysters and corals have difficulties producing shells and skeletons in more acidic seawater, diatoms are thought to be less susceptible to the impacts of ocean acidification — a chemical alteration caused by the accumulation of carbon dioxide (CO2). The widely distributed small diatoms construct their shells from silica, a compound of silicon, oxygen, and hydrogen.
Diatoms are a form of plankton, commonly known as phytoplankton, which is the most prevalent type of plankton. According to University College London, these photosynthesising algae contain a siliceous skeleton (frustule) and are present in virtually every aquatic habitat, including fresh and saltwater as well as soil.
Intriguingly, they are also the most significant producers of plant biomass in the ocean and contribute to carrying carbon dioxide (CO2) into the deep ocean, regulating our climate. Since diatoms construct their shells from silica rather than calcium carbonate, it was previously believed that they would benefit from ocean acidification. This is a chemical alteration in saltwater caused by the increased intake of carbon dioxide, which makes calcification more challenging.
In a new study published in Nature, scientists demonstrate that this chemical shift also affects diatoms. According to analyses of data from field experiments and model simulations, ocean acidification could have a significant impact on diatom populations.
In this study, scientists from the GEOMAR Helmholtz Centre for Ocean Research in Kiel, the Institute of Geological and Nuclear Sciences Limited in New Zealand, and the University of Tasmania combined an overall analysis of many data sources with Earth system modelling.
Due to the acidity of the ocean, the silicon shells of diatoms dissolve more slowly. This is not a benefit, according to a press release from GEOMAR. It causes the diatoms to descend into deeper water layers prior to their chemical dissolution and transformation into silica. Therefore, this nutrient is exported more efficiently to the deep ocean, making it scarcer in the light-flooded surface layer, where it is required to create new shells. This results in a decrease in diatoms.
Diatoms account for 40% of the ocean’s plant biomass output and serve as the foundation of numerous marine food webs. The addendum indicates that they are also the primary motor of the biological carbon pump that transfers CO2 into the deep ocean for long-term storage.
The current understanding of the ecological implications of ocean change is mostly based on small-scale research conducted at a specific location and time. These results can be misleading if the intricacy of the Earth’s system is ignored. The study employs diatoms as a case study to illustrate how small-scale influences can result in ocean-wide alterations with unanticipated and far-reaching implications on marine ecosystems and matter cycles. Given that diatoms are one of the most important plankton groups in the ocean, their reduction could result in a substantial shift in the marine food web or possibly a change in the ocean’s capacity as a carbon sink.
