Maerl-forming coralline algae and associated phytobenthos from the Maltese Islands

Abstract

Maerl grounds consist mainly of unattached non-geniculate coralline algae, known as 'rhodoliths, and their alga1 debris. The recent discovery of such grounds around the Maltese Islands led to the present study of rhodoli$-forming species. Gross morphology of the rhodoliths was highly variable so identifications were based on microscopic examination of fertile material. Investigations using optical and scanning electron microscopy confirmed that :five main species of rhodolith- forming coralline algae were present: Lithophyllum racemus, Lithothamnion corallioides, Lithothamnion minervae, Mesophyllum alternans and Phymatolithon calcareum. Two other heavily calcified species, tentatively identified as Peyssonnelia rosa-marina and Neogoniolithon brassica-florida on the basis of gross morphology, were also important contributors to Maltese maerl deposits. Seasonal monitoring of the phytobenthos associated with maerl revealed that Flabellia petiolata and Womersleyella setacea were consistently the dominant species present.