Alien bryozoans in the fouling assemblage of Quequén Harbour (Argentina, Southwest Atlantic)

Abstract

The bryozoan fauna reported for Argentine harbours encompasses at least 29 species, of which only nine are documented exotics and another four were regarded as cryptogenic. In comparison with other marine harbours in the area, Quequén Harbour (QH) was thought to be characterized by a relatively low bryozoan diversity, probably due to its estuarine features. Two species had been previously recorded during a detailed taxonomic study of their bryozoan assemblages: Cryptosula pallasiana (Moll) and Conopeum sp. Four other bryozoans had also been listed for QH in the ecological literature, but their presence was not confirmed by taxonomic studies or by voucher specimens deposited in museum collections: Bugula flabellata (Thompson), Bugula neritina (Linné), Bowerbankia sp. and Conopeum reticulum (Linné). Forty-eight rectangular (210 × 260 × 3.5 mm) low-density polyethylene panels screwed to four vertical supporting structures were suspended from a pier (38º 34.310' S, 58º 42.814' W) on September 20, 2012 (winter) and collected on June 21, 2013 (autumn). In previous contributions, we reported the presence of four other alien species in QH: Fenestrulina delicia Winston et al., Zoobotryon verticillatum (Delle Chiaje), Aspidelectra melolontha (Landsborough) and Schizoporella errata (Waters). In addition, the alien Conopeum seurati (Canu), the cryptogenic Electra monostachys (Busk) and the native Membranipora puelcha (d’Orbigny) were recently discovered encrusting the panel surfaces, and the presence of Conopeum reticulum was also confirmed. The total number of bryozoans in QH reaches therefore 12 species. The increasing number of alien species in QH detected after 25 years highlights the importance of performing periodical surveys in harbour environments, which are the most common initial incursion sites used by non-indigenous species.