Researches on marine benthic organisms around the Flegrean islands in the Gulf of Naples have been traditionally performed at the Stazione Zoologica since its foundation in 1872. The peculiarity of this area is strictly related to its geographic location, corrisponding to the winter surface isotherm of 14°C that cuts the Mediterranean Sea into two and represents a climatic boundary barrier for species with different biogeographic affinities. The richness in marine species and habitats of this area (including the islands of Ischia, Procida and Vivara) is preserved by the establishment in 2008 of the Marine Protected Area ‘Regno di Nettuno’.
One of the most important habitat of the Gulf of Naples is represented by the Posidonia oceanica beds, an endemic seagrass that forms around the island of Ischia a continuous belt, from 0.5 m down to 38 m in depth, covering about 1700ha of the seafloor. Several meadows have been studied by the Benthic Group, located at Villa Dohrn on the Island of Ischia: Scarrupata di Barano, Cava dell’Isola, La Nave, San Pietro, Castello Aragonese and Lacco Ameno.
The best-known meadow is that of Lacco Ameno (LA), studied since 1976, and located in the northern part of the island, in the bay bounded by ‘Monte Vico’ and the city of Lacco Ameno (40,7598 N, 13,900 E). Only in this station, the meadow is continuous from 0.5 m down to 32 m in depth and it covers an area of about 308 ha.
In this pilot site (Station LTER-LA), a significant variability at different spatial and temporal scales has been recorded for plant descriptors and associated communities. In particular, at 5 and 10 m depths, a decrease in meadow density (a descriptor of the ecological status of a meadow, widely used by many authors to indicate the plant abundance) is evident since the end of 1980. This fact seems to suggest an increase in the anthropic pressure, even if other factors, such as physical disturbance, topographic complexity and nutrient availability, might operate to modify this system.
The high plasticity of P. oceanica, which responds to a wide range of environmental conditions, have driven our researches towards the study of the effects of climatic changes, such as ocean acidifcation, on this vegetated system. Issues associated to climate changes are being approached also by the comparison with another Ischia P.oceanica meadow. This is located at Castello Aragonese (40,73083°N 13,96310°E), on the east side of the island, where a number of vents which release CO2 affect the P. oceanica system. These CO2 vents are unusual in that they are not heated and neither do they produce toxic compounds, providing a natural laboratory for the study of the ecosystem level effects of ocean acidification.
