Dorgali, specimens of blue crab found in the Grotta del Bue Marino: «Threat to the ecosystem»

The blue crab, the "nightmare" of the Italian seas, manages to push itself and survive even in extreme and fragile ecosystems such as sea caves.

The discovery took place in the most important biodiversity hotspot in the world, namely the Grotta del Bue Marino, on the coast of Dorgali ( WATCH THE VIDEO ).

Here the volunteer speleodivers of the Phreatic APS association have been supporting the researchers of the Italian Speleological Society in the environmental monitoring activities of this delicate underground environment since last year.

"It is the first year that we have observed the blue crab in the seas of the Gulf of Orosei but we never thought we would find several specimens in the cave too, and what's more they have penetrated more than half a kilometer from the entrance and in two branches of the system. We were amazed and immediately alerted the researchers", explains Andrea Marassich, speleo diver and president of Phreatic APS.

Callinectes sapidus , commonly known as the Atlantic blue swimming crab, is a crustacean native to the American side of the Atlantic Ocean and arrived in the Mediterranean through the ballast water of commercial ships.

Although they are good swimmers, these crustaceans remain tied to life on the seabed. However, they have a larval stage that lives in the water column and is passively transported by currents, ending up colonizing new areas.

What worries scientists is that the blue crab is known as an eclectic predator that feeds on a vast range of prey and essentially on everything it finds in its path: its presence in the cave could therefore represent a threat to adapted organisms to underground life, which are often few in number and vulnerable.

Additionally, the blue crab population could grow rapidly in the absence of natural predators.

«We are faced with a serious and concrete threat to the ecosystem because the blue crab is a large predator and we did not expect it to enter caves, which are environments with scarce food resources - explains Fabio Stoch, researcher at the Free University of Brussels , internationally renowned biospeleologist, now involved in the Bue Marino monitoring project.

«Instead the blue crab is there and adapts, and having found it so far from the entrance makes us understand how invasive this alien species can be. If it begins to reproduce and invade those spaces constantly, it could cause the disappearance of endemic species, i.e. exclusive to that cave, which exist in small and fragile communities, and therefore lead to the destruction of the entire habitat, with a chain reaction that would influence the entire surrounding environment ."

Another reason for alarm is that the presence of the blue crab in the Grotta del Bue Marino does not seem occasional or sporadic: the specimens were in fact found at different distances inside the cave, over 500 meters from the entrance, both in the North Branch and in the Middle Branch.

The habitat of sea caves is of community interest, therefore protected and must be protected in all possible ways.

«In the specific case of the Bue Marino, the use of pots can free the first sections of the tunnels from the largest specimens, but an intervention that is more timely and repeated over time than ever would be needed, before it is too late, but – concludes Stoch – they are pessimistic in this regard, and furthermore biological monitoring should be extended to other sea caves."

(Unioneonline/lf)