By David Fernandez Guerrero
The oceans, like forests, capture part of the carbon dioxide emissions that human activity generates. However, in the case of the deep sea, the accumulation of this gas translates into an increase in the acidity of the seas. An average increase of close to 30% since the industrial revolution began its journey, more than 200 years ago. And that by the end of the century it can reach 150%. It is a phenomenon that can endanger the survival of coral habitats and threaten the animals that live in them, according to a study published in the journal Proceedings of the Royal Society B.
The authors of the work have investigated with robots and divers the seabed of a group of upwellings - outlets of water masses towards the surface - at a depth of 40 meters. These were in the archipelago of the Columbretas, 56 kilometers away from the coast of Castellón. Why study them? In the first place, because “they serve as a laboratory for what will happen” due to the carbon dioxide they emit, explains Cristina Linares, a researcher at the University of Barcelona (UB) and one of the authors of the study: “PH values [acidity ] that we observe in the upwellings are 7.8 or 7.9, very similar to what is forecast for the end of the century ”. In the surroundings, the PH is 8.1. A team of scientists from the UB, the University of Girona, the CSIC and the Anton Dohrn Zoological Station in Italy has carried out the work.
The authors of the work have investigated with robots and divers the seabed of a group of upwellings - outlets of water masses towards the surface - at a depth of 40 meters. A team of scientists from the UB, the University of Girona, the CSIC and the Anton Dohrn Zoological Station in Italy has carried out the work.
These depths, moreover, are usually home to calcified corals and algae. One of the “most significant habitats in the Mediterranean”, due to the complexity of the ecosystems they host, according to the authors of the work. Multiple species of fish and crustaceans, such as grouper and red lobster "use the coral habitat to survive," explains Linares.
It is not the first study to be published on this topic. However, other investigations focused on "shallower areas [between three and five meters deep] with divers" or deeper environments [more than 150 meters] with underwater robots, explains Linares. In the case of his work team, however, it has been possible to combine the use of “robots to look at the entire extension of the upwelling zone” with the work of divers to “study the communities in more detail than what the robots ”. This has been feasible because the researchers have a long "experience in scientific diving", says the scientist. The work methodology consisted of taking samples of the terrain around the upwellings.
Although the study authors admit that it is necessary to follow the evolution of the analyzed seabed in the long term, their conclusions are worrying. Coralline algae cannot survive in such an acidic environment. The corals either. Only some of them - the rose-marine, calcified algae with microcrystals of aragonite, instead of magnesium - remain near the upwellings. The place of corals is occupied by fleshy-stemmed algae, such as kelp, which are normally found below 65 meters in depth.
What are the consequences of the findings? Linares explains that the level of acidity in the marine areas studied is similar to what the oceans will have at the end of the century, if carbon dioxide emissions are not reduced. Therefore, the survival of coral habitats will be compromised. And with this, "species of animals that use it to survive" such as grouper and red lobster will be affected, explains Linares. For the same reason, an impact on the economy must be expected, while a decrease in the number of catches is expected, the researcher reasons. And it is that "small changes in the acidity of the water can produce radical changes in the distribution of ecosystems", concludes the study.