Ocean acidification and sea warming-toward a better comprehension of its consequences

Climate change, rigorously heralded more than thirty years ago as a real threat, has become the most pressing and pernicious global problem for the entire planet. In conjunction with local impacts such as fishing, eutrophication or the invasion of alien species, to give just a few examples, the acidification of the oceans and the warming of the sea began to show its effects more than twenty years ago. These signals were ignored at the time by the governing bodies and by the economic stakeholders, who now see how we must run to repair the huge inflicted damage. Today, different processes are accelerating, and the thermodynamic machine has definitely deteriorated. We see, for example, that the intensity and magnitude of hurricanes and typhoons has increased. Most models announce more devastation of flash floods and a decomposition in the water cycle, which are factors directly affecting ecosystems all over the world. Important advances are also observed in the forecasting of impacts of atmospheric phenomena in coastal areas with more and more accurate models. Rising temperatures and acidification already affect many organisms, impacting the entire food chain. All organisms, pelagic or benthic, will be affected directly or indirectly by climate change at all depths and in all the latitudes. The impact will be non-homogeneous. In certain areas it will be more drastic than in others, and the visualization of such impacts is already ongoing. Some things may be very evident, such as coral mortalities in tropical areas or in the surface waters of the Mediterranean, while others may be less visible, such as changes in microelement availability affecting plankton productivity. In fact, primary productivity in microalgae, macroalgae and phanerogams is already beginning to feel the impact of warmer, stratified and nutrient-poor waters in many parts of the planet. Nutrients are becoming less available, temperature is rising above certain tolerance limits and water movement (turbulence) may change in certain areas favoring certain species of microplankton instead of others. All these mechanisms, together with light availability (which, in principle, is not drastically changing except for the cloudiness), affect the growth of the organisms that can photosynthesize and produce oxygen and organic matter for the rest of the trophic chain. That shift in productivity completely changes the rest of the food chain. In the Arctic or Antarctic, the problem is slightly different. Life depends on the dynamics of ice that is subject to seasonal changes. But winter solidification and summer dissolution is undergoing profound changes, causing organisms that are adapted to that rhythm of ice change to be under pressure. The change is more evident in the North Pole, but is also visible in the South pole, where the sea ice cover has also dramatically changed. In the chapter there is also a mention about the general problem of the water currents and their profound change do greenhouse gas effects. The warming of the waters and their influence on the marine currents are also already affecting the different ocean habitats. The slowdown of certain processes is causing an acceleration in the deoxygenation of the deepest areas and therefore an impact on the fragile communities of cold corals that populate large areas of our planet. Many organisms will be affected in their dispersion and their ability to colonize new areas or maintain a connection between different populations. The rapid adaptations to these new changes are apparent. Nature is on its course of restart from these new changes, but in this transitional phase the complexity and interactions that have taken thousands or millions of years to form can fade away until a new normal is consolidated.

Rossi S., 2022. Ocean acidification and sea warming-toward a better comprehension of its consequences. In: Rossi S. (Ed.), SDG 14: life below water, pp 111-205. London: Springer, Cham. Chapter (restricted access).


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