Global warming and acidification of the oceans reduce the capacity of calcareous phytoplankton to absorb CO2 from the atmosphere.
The rapid warming and acidification of the oceans causes negative impacts on the calcareous microalgae that are important regulators of the concentration of CO2 in the atmosphere and as consequence in the process of global climate regulation. The oceans absorbing more than a quarter of the carbon dioxide (CO2) emitted over the last century by the impact of anthropogenic activities, the oceans have changed their chemical characteristics, resulting in a decrease in pH and acidification. The changes also affect other organisms of zooplankton and phytoplankton as well as foraminiferas, corals, echinoderms, crustaceans and mollusks.
Calcareous microalgae are important regulators of the concentration of CO2 in the atmosphere. Researchers warn of the negative impacts of rapid warming and acidification of the oceans on these marine organisms, and consequently in the process of global climate regulation.
Different morphological categories. (A) Normal cocolito (b) Cocolito malformado. Source: (Milner et al., 2016)
The oceans, absorbing more than a quarter of the carbon dioxide (CO2) emitted in the last century by anthropogenic activities, have been changing their chemical characteristics, resulting in the decrease of pH, called “acidification of the oceans.
The CO2 dissolved in the water also increases the concentration of the hydrogen ion in the water, thus lowering the pH. Estimates indicate that between 1751 and 1994 the pH of the surface of the oceans has decreased from 8.179 to 8.104, which represents a change of -075.
It has been reported that this decrease in pH will have negative consequences for marine organisms, especially those using calcium carbonate, calcite or aragonite, to build their cell covers or skeletons.
Under normal conditions, calcite and aragonite are stable in surface waters because the carbonate ion is in supersaturated concentrations. However, as the pH drops, so does the concentration of this ion, and when the carbonate becomes unsaturated, the cellular structures constructed with calcium carbonate become vulnerable to dissolution.
Researches has found that reducing calcification and increasing the dissolution of cellular structures in a scenario with high concentrations of CO2 could affect cocolitophorids, foraminiferas, corals, echinoderms, crustaceans and molluscs, among others organisms.
In addition, the progressive increase in the global average temperatures of the atmosphere also increases the surface temperature of the sea. According to projections of emissions of greenhouse gases of the IPCC (Intergovernmental Group of Experts on the Climate Change) is predicted for the next decades, a worsening of the risks posed by the warming and the acidification of the seas.
Researchers from the Institute of Environmental Science and Technology of the Autonomous University of Barcelona (ICTA-UAB), the University of Cambridge and the UK Marine Biology Association recently warned of the negative impacts of rapid ocean warming And its acidification on the cocolitofóridos. These are calcareou organisms constituents of marine phytoplankton, and consequently involved in the process of regulating the concentrations of carbon dioxide in (CO2) the atmosphere.
In a study published in the journal Limnology & Oceanography and Biogeosciences, it is reported that increasing sea surface temperature may exacerbate the impacts of ocean acidification on calcareous phytoplankton, hampering its evolutionary success and physiological performance. In addition, these changes will contribute to maximize the concentration of atmospheric CO2.
Plankton in the carbon cycle.
Plankton includes heterotrophic organisms such as animals, protists and bacteria, commonly called zooplankton and autotrophic organisms such as plants, other unicellular and bacteria, called phytoplankton. The organisms most abundant in phytoplankton are cyanobacteria and diatoms, which are the basis of the marine trophic weft.
Marine phytoplankton, in addition to absorbing a significant proportion of the carbon in the atmosphere, produces 50% of the molecular oxygen required for terrestrial life. Phytoplankton develops in conditions of sunlight and abundant nutrients. These organisms elaborate their food through photosynthesis, that is, turning inorganic matter into organic matter with the energy of light. It is possible to emphasize that the life in the Earth is maintained thanks to the photosynthesis that the plants realize in the continents, in conjunction with algae of water, as they have the capacity to release oxygen and synthesize organic matter for it available for use by other organisms through the flows of matter and energy.