The macrobenthic species of the infralittoral to circalittoral transition zone off the northeastern coast of Malta (Central Mediterranean)

Abstract

The macrobenthic assemblages of the sedimentary bottoms off the northeastern coast of Malta were studied during the summer of 1993. Crab and dredge samples were collected from depths of 21-75tn from an area of approximately 48 km2 off Comino, Mellieha Bay and St. Paul's Bay. Below ctr. 40m the bottorn was predominantly sandy with meadows of Posidonia oceanica, giving way to bare sand it1 the lower infralittoral. Between 45rn and 75r11, the bottom consisted of organogenic gravel with abundunt free-living culcureous rhodophytes, predominantly the corallines Phymatolithon calcareum and Lithothamnion corallioides. Such bot~oms, known as maerl, have not been reported previously from the Maltese Islands. 19 species of macroalgae, I phanerogam, and 108 species of macrofaunu were recorded, the bulk of these from the maerl bottom. An additional 122 species of molluscs occurred as etnpty shells. Maerl bottoms support a high species richness, even if abundance is low. There is evidence to suggest that maerl is the predominant bottom type all along the northeastern coast of the Maltese Islands in the tramition between the lower infralittoral and the circalittoral, which occurs at depths of 45-75m.