Baseline marine benthic surveys in the Maltese Islands (Central Mediterranean)

Abstract

During the period 1991 to 1997, extensive baseline studies of the submarine geomorphology, infralittoral habitats, macrobenthic assemblages, and demersal fish fauna, were carried out in 14 different sites around the Maltese Islands, using conventional SCUBA diving techniques. These were made as part of assessments of the environmental impact of existing or proposed projects, or in order to produce an inventory of coastal resources. In total, these surveys covered a sea-bed area of ca. 7.55Km² and a coastline length of ca 24 km, and represent the most extensive biological surveys of the marine environment carried out to date in the Maltese Islands. The results of these surveys have been presented as maps showing the type, location, and spatial extent of these physical and biological features. The Peres & Picard (1964) scheme, as adapted by Pen~s (1967; 1982) was used to classify and characterize the benthic assemblages recorded during the surveys. Our results show that, in tenus of spatial extent, the most important macrobenthic assemblages are the communities of photophilic 'algae on hard substrata, meadows of the sea-grass Posidonia oceanica and communities of bare well-sorted sand. For all these, many subtypes and facies exist, depending on the light intensity, hydrodynamic conditions, microtopography, sediment granulometry and other edaphic factors, and anthropic influences, including pollution. Other assemblages with a limited spatial distribution include meadows of the sea-grass (vmodocea nodosa and of the Lessepsian immigrant Halophila stipu/acea on sandy bottoms, the assemblages of boulder fields which are complexes of photophilic and sciaphilic communities, and those of marine caves. Our maps are supplemented by descriptions of the different habitats and macrobenthjc assemblages, species lists, and semi-quantitative data on percentage cover for the dominant macroalgae, shoot density counts for sea-grass meadows, and population density counts for the main macrofaunal species. These maps and data-sets are intended to be used (i) for assessing the status of habitats, species assemblages, and individual species, around the Maltese Islands in order to recommend appropriate measures for their conservation, including inclusion in red data lists; (ii) for designation of marine protected areas; and (iii) as baselines against which future monitoring studies and surveys can be compared.