It was only a matter of time : occurrence of Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini in the Maltese Islands (Chlorophyta, Ulvophyceae, Caulerpaceae)

Abstract

A new alien species of Caulerpa, corresponding morphologically to Caulerpa taxifolia (Vahl) C. Agardh var. distichophylla (Sonder) Verlaque, Huisman and Procaccini, already known from Turkey, Sicily, and Cyprus, was first discovered in Malta in June 2013. The original record was of but a few fronds, and surveys made during winter at the same site did not locate any plants. A survey conducted during July 2014, however, located two patches of the alga occupying a total area of ca 125m2 in the 4–6m depth range, with a mean frond density of 276.3 (± 51.21 SD) per m2. Also in July 2014, two patches with a total of 520 fronds in an area of 0.37m2 at 14–15m depth were found at a second site ca 7.4 km along-coast distance from the first site. The alien algae formed part of a photophilic assemblage growing on rock in clearings adjacent to Posidonia oceanica (Linnaeus) Delile stands. The most likely source of the Maltese populations is Sicily, and the most likely vector is recreational and/or commercial shipping.