Germling culture and molecular analysis of evasive micro-filamentous green algae growing in the Maltese islands (central Mediterranean)

Abstract

Various species of marine micro-filamentous green algae (<5 mm) remain overlooked globally. They are difficult to identify in field collections due to their diminutive size and their cryptic morphology. During this study, algal cultures combined with DNA barcoding helped to overcome these challenges. Both substratum samples and macrophytic fragments of Posidonia oceanica, Dictyopteris sp. and Halopteris sp. were incubated in laboratory culture. Germlings of Ulvella endostraca and Blastophysa rhizopus grew from the incubated substratum. Blastophysa rhizopus is a new record for the Maltese islands, as is U. endostraca that had only been reported previously from New Zealand. In situ, germlings of both species were also observed to grow as epiphytes, on Dictyopteris sp. in the case of U. endostraca, and on P. oceanica in the case of B. rhizopus. This study employed the in vitro culture of algal germlings, as well as morphological and molecular analyses. DNA data and subsequent phylogenetic analyses of tufA and rbcL sequences supported the separation of U. endostraca from other closely related congeners that have been previously reported from the Maltese islands. Moreover, this study includes a comparison of the micro-filamentous algae identified from Malta with those from other areas of the Mediterranean Sea.