Invasions of the non-indigenous red alga Lophocladia lallemandii (Montagne) F. Schmitz off the Island of Ischia (Tyrrhenian Sea, Italy)

This paper describes the distribution and spread of the non-indigenous red alga Lophocladia lallemandii (Montagne) F. Schmitz along the coast of the Island of Ischia (Tyrrhenian Sea, Italy). Lophocladia lallemandii was monitored through surveys from July 2019 to January 2020 at the Capo Sant’Angelo (Ischia), where L. lallemandii was observed, but not reported, in the years preceding the invasion of the upper rocky infralittoral shore reported here. It is noteworthy that a large portion of the study area is included within one of the two “B no-take” zones of the Marine Protected Area of the “Regno di Nettuno” (“Neptune’s Realm”). During the surveys, the alga was first observed in the middle of July 2019 and totally disappeared by the middle of January 2020. Algal cover showed two peaks in August (55%) and November (58.5%). Fertile thalli (tetrasporophytes) of L. lallemandii were observed in all of the analysed samples. Thalli were not always strongly attached to the substrate or other algae and could often be easily detached by strong hydrodynamic conditions. These detached thalli were found laying on the bottom in dense turfs or floating or stranding on the beach. Noteworthy were the macroflora and fauna, the latter essentially composed by mollusks and amphipods, living among the branches of the alga, and various fishes hiding within the thick algal turf. These observations indicate that this alga may be a source of food and refuge for the native animal community of the upper rocky infralittoral zone.