The vents phenomena in Ischia
Ischia is a volcanic island where geology and biology are closely linked.Along its coasts there are special sites called ‘vents‘, where bubbles of carbon dioxide (CO2) are released from the seabed. This causes a lowering of the pH of the water, altering its physicochemical properties and causing local marine acidification. Lowering the pH of the oceans and altering the physical-chemical properties of water is a phenomenon already known to scientists globally, known as “ocean acidification.”
This phenomenon can cause some adverse effects on marine organisms, especially those that build a calcareous skeleton, such as corals and mollusks. Both in the Mediterranean and elsewhere in the rest of the world there are other systems of vents similar to that of Ischia. These sites are very important because they represent natural laboratories that allow us to study and understand the effect of environmental changes expected in the near future, both on individual species and on entire communities.
CO2 systems at the Aragonese Castle
One of the CO2 best known, and the first in the world to be studied to understand the effects of acidification on marine organisms, is the one located at the Aragonese Castle of Ischia. At this site there is an ‘intense emission of carbon dioxide and therefore a gradient of acidification of the water originates, which starts from extremely low values and then reaches the ambient pH values, which as far as the Mediterranean Sea is concerned are around pH ~8.0.
The emission zone also extends on both the south and north sides of the Aragonese Castle. The habitats that characterize these sites are mainly shallow hard bottoms vegetated with dense macroalgae cover with attached prairie of Posidonia oceanica, one of the most important marine plants in the Mediterranean and of which there is a dense prairie right in the waters around the Castello.
Global CO2 effect. A possible solution
The ‘ocean plays a key climate role on a global scale, absorbing about 25 percent of the carbon dioxide we produce, making it an extremely important climate “regulator.” Understanding the phenomenon of ocean acidification through the use of these natural marine laboratories, such as the vents of Ischia, turns out to be crucial to get an idea of what will happen in the near future.
This also allows us to think of possible nature-based solutions to be able to mitigate it. Preserving seagrasses such as the Posidonia oceanica and carrying out actions to restore their habitat are some possible solutions to reduce in a sustainable form the effects of ocean acidification and anthropogenic impacts in order to restore the health of our sea.
Suspended between two horizons: a view halfway between the emerged and submerged landscape of the Aragonese Castle where the gaseous CO2. Photo: Pasquale Vassallo
What’s boiling in the pot? Detail of one of the submerged areas of the Aragonese Castle characterized by intense CO2 Where a dense cover of macroalgae on surface rocky substrate can be seen. Photo: Pasquale Vassallo
A sunken garden: In the background the prairie of Posidonia oceanica and a shoal of Sarpa salpa, main herbivorous fish in the Mediterranean. Photo: Pasquale Vassallo
Peaceful coexistence: Detail of a vegetated habitat characterized by patches of Posidonia oceanica and macroalgae of different species sharing space with the well-known orange encrusting sponge: Crambe crambe. Photo: Pasquale Vassallo
I stagger but not MOLLuscO: gastropod mollusk of the genus Patella which has a bleached shell due to the corrosive action caused by the lowering of pH, within sites with CO2. Photo: Pasquale Vassallo
I work below the surface: underwater scientific operators conducting a photographic transect for biodiversity assessment along the acidification gradient at the Aragonese Castle. Photo: Jeremy Carlot
