Marine invasive species represent a growing threat to the biodiversity of the Costa Brava. Introduced, in many cases, accidentally, these species can displace native ones, alter the balance of ecosystems, and cause significant ecological imbalances.
Areas such as the mouth of the River Ter, the Medes Islands, and Cap de Creus are particularly sensitive zones. They are currently being monitored by scientists and local organizations to control their spread and minimize their impact.
Main invasive species and their impact on the Costa Brava
1. Blue crab (Callinectes sapidus)
Originally from the North American Atlantic coast, the blue crab has colonized estuaries such as the mouth of the River Ter. It is a highly competitive species that displaces local crabs and other benthic organisms. Its presence alters the marine food chain and competes intensely for resources. First detected in the Ebro Delta in 2017, it has become established in the area and, interestingly, has found a place in the local cuisine.
2. Caulerpa taxifolia
This invasive alga, originally from aquariums, has been detected in several areas of Cap de Creus and the Medes Islands. It forms dense carpets on the seabed, covering seagrass meadows of Posidonia and preventing the development of native species. Its aggressiveness earned it the nickname “killer alga,” popularized in the 1990s due to its rapid spread along the French Mediterranean coast.
3. Asparagopsis taxiformis
Red alga of tropical origin recently detected in the Marine Reserve of the Medes Islands. In spring 2024, its population multiplied by 30 compared to 2023. Its spread threatens to displace key species such as Posidonia oceanica.
How to combat marine invasive species
The most effective way to contribute to the fight against marine invasive species is to actively participate in their early detection and management. Joining local initiatives such as the MINKA Project allows people to provide georeferenced data on marine and terrestrial organisms, collected by the community itself and analyzed by experts. This citizen science platform encourages anyone to share their observations on a personal profile, generate discussion about them, and later access professional validation and expert opinions, thereby promoting biodiversity conservation.
