Capítulo 6. Invertebrados marinos alóctonos en el Mar Menor

Résumé

The current configuration of the Mar Menor lagoon is the result of a series of geomorphologic processes brought about by natural dynamics. However, from the 18th century onwards human activity has been the main driving force behind its transformation. Each of these changes has prompted alterations in the lagoon’s landscape and changes in its community structure. The artificial connection between the lagoon and the Mediterranean Sea has eliminated or lowered some of the ecological barriers between the two bodies of water, reducing differences between the values of parameters such as salinity or temperature. This in turn has led to the disappearance of environmental barriers, allowing new species to enter and establish themselves in the lagoon. Numerous alien species, some of which can be considered invasive, compete with native species, driving them out and changing the traditional landscape of the lagoon. Despite the obvious effect on the environment, the real impact of most alien species remains unknown and the consequences of an invasion are often not easy to predict. The 1990s saw the arrival of species commonly found in the Mediterranean Sea, such as the jellyfish Cotylorhiza tuberculata (Macri, 1778) and Rhizostoma Pulmo (Macri, 1778), in the form of massive blooms, or of other species that play an important ecological role, such as the noble pen shell Pinna nobilis (Linnaeus, 1758). In recent years other species, this time considered invasive in the Mediterranean, such as the comb jelly Mnemiopsis leidy (Agassiz, 1865), the sea hare Bursatella leachii (De Blainville, 1817) or the fan worm Branchiomma bairdi (McIntosh, 1885), have also become commonplace. Most of them enter the lagoon through the El Estacio channel, although activities such as angling are the vector of entry of species in the form of live bait, such as the Korean ragworm Perinereis linea (Treadwell, 1936). Numerous species have also arrived on the hulls of ships and subsequently made their home in docks and breakwaters: ever since harbours and ports began to proliferate on the coast of the lagoon species such as the barnacle Amphibalanus amphitrite (Darwin, 1854) have started to appear. Vessels are a constant and continuous input vector for species such as the sponge Haliclona (Haliclona) oculata (Linnaeus, 1759), the bryozoan Bugula stolinifera (Ryland, 1960) or the sea squirts Ciona intestinalis (Linneaeus, 1767) and Styela canopus (Savigny, 1816), all cited as alien species in the Mediterranean. Many of them have a significant environmental and socio-economic impact, with negative consequences for the tourist industry