Hidden in plain sight: species richness and habitat characterisation of sublittoral pebble beds

Sublittoral pebble beds are generally considered to be impoverished, but the physical and biological characteristics of these habitats are poorly known. We characterised nineteen pebble bed sites in the Maltese Islands, providing detailed habitat data for Mediterranean sublittoral pebble beds for the first time. Nearly 40,000 individuals belonging to 332 taxa were recorded in all, with total richness estimated to reach 440 taxa; molluscs, crustaceans and polychaetes were the most diverse faunal groups. This high diversity is likely due to the structural complexity of the pebble beds, which had a vertically stratified arrangement of sediment particles that is likely maintained through periodic physical disturbance. Variation in the biotic assemblage from site to site was correlated with changes in the quantity of sand and silt, with the area of the pebble bed, with water depth, and with the thickness of the pebble layer. This indicates that pebble-bed macrofaunal assemblages are sensitive to changes in hydrodynamic conditions and sediment loading, to alterations to the stratification of the pebble beds, and to fragmentation of the habitat patches. These results contradict assertions that sublittoral pebble beds are impoverished, instead showing that they can be highly diverse habitats supporting biotic assemblages that respond to a complex set of environmental variables. The present findings enable better understanding of the ecological importance of pebble beds and of the potential impacts of anthropogenic disturbance, enabling more informed decisions for habitat conservation and management

Wanted dead or alive : high diversity of macroinvertebrates associated with living and ’dead’ Posidonia oceanica matte

The Mediterranean endemic seagrass Posidonia oceanica forms beds characterised by a dense leaf canopy and a thick root-rhizome ‘matte’. Death of P. oceanica shoots leads to exposure of the underlying matte, which can persist for many years, and is termed ‘dead’ matte. Traditionally, dead matte has been regarded as a degraded habitat. To test whether this assumption was true, the motile macroinvertebrates of adjacent living (with shoots) and dead (without shoots) matte of P. oceanica were sampled in four different plots located at the same depth (5–6 m) in Mellieha Bay, Malta (central Mediterranean). The total number of species and abundance were significantly higher (ANOVA; P<0.05 and P<0.01, respectively) in the dead matte than in living P. oceanica matte, despite the presence of the foliar canopy in the latter. Multivariate analysis (MDS) clearly showed two main groups of assemblages, corresponding to the two matte types. The amphipods Leptocheirus guttatus and Maera grossimana, and the polychaete Nereis rava contributed most to the dissimilarity between the two different matte types. Several unique properties of the dead matte contributing to the unexpected higher number of species and abundance of motile macroinvertebrates associated with this habitat are discussed. The findings have important implications for the conservation of bare P. oceanica matte, which has been generally viewed as a habitat of low ecological value.peer-reviewe

Desmophyllum dianthus (Esper, 1794) in the scleractinian phylogeny and its intraspecific diversity

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 7 (2012): e50215, doi:10.1371/journal.pone.0050215.The cosmopolitan solitary deep-water scleractinian coral Desmophyllum dianthus (Esper, 1794) was selected as a representative model species of the polyphyletic Caryophylliidae family to (1) examine phylogenetic relationships with respect to the principal Scleractinia taxa, (2) check population structure, (3) test the widespread connectivity hypothesis and (4) assess the utility of different nuclear and mitochondrial markers currently in use. To carry out these goals, DNA sequence data from nuclear (ITS and 28S) and mitochondrial (16S and COI) markers were analyzed for several coral species and for Mediterranean populations of D. dianthus. Three phylogenetic methodologies (ML, MP and BI), based on data from the four molecular markers, all supported D. dianthus as clearly belonging to the “robust” clade, in which the species Lophelia pertusa and D. dianthus not only grouped together, but also shared haplotypes for some DNA markers. Molecular results also showed shared haplotypes among D. dianthus populations distributed in regions separated by several thousands of kilometers and by clear geographic barriers. These results could reflect limited molecular and morphological taxonomic resolution rather than real widespread connectivity. Additional studies are needed in order to find molecular markers and morphological features able to disentangle the complex phylogenetic relationship in the Order Scleractinia and to differentiate isolated populations, thus avoiding the homoplasy found in some morphological characters that are still considered in the literature.This study was funded by CTM2009-00496 and CGL2011-23306 projects of the “Ministerio de Ciencia e Innovación” (Spain). Research at sea was partly supported by the European Commission F. P.VI Project HERMES Contract No. GOCE-CT-2005-511234-1) and the EU F.P. VII Project HERMIONE(contract number no. 226354)

European Red List of Habitats Part 1. Marine habitats

The European Red List of Habitats provides an overview of the risk of collapse (degree of endangerment) of marine, terrestrial and freshwater habitats in the European Union (EU28) and adjacent regions (EU28+), based on a consistent set of categories and criteria, and detailed data and expert knowledge from involved countries1. A total of 257 benthic marine habitat types were assessed. In total, 19% (EU28) and 18% (EU28+) of the evaluated habitats were assessed as threatened in categories Critically Endangered, Endangered and Vulnerable. An additional 12% were Near Threatened in the EU28 and 11% in the EU28+. These figures are approximately doubled if Data Deficient habitats are excluded. The percentage of threatened habitat types differs across the regional seas. The highest proportion of threatened habitats in the EU28 was found in the Mediterranean Sea (32%), followed by the North-East Atlantic (23%), the Black Sea (13%) and then the Baltic Sea (8%). There was a similar pattern in the EU28+. The most frequently cited pressures and threats were similar across the four regional seas: pollution (eutrophication), biological resource use other than agriculture or forestry (mainly fishing but also aquaculture), natural system modifications (e.g. dredging and sea defence works), urbanisation and climate change. Even for habitats where the assessment outcome was Data Deficient, the Red List assessment process has resulted in the compilation of a substantial body of useful information to support the conservation of marine habitats

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

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.peer-reviewe

Occurrence of Paraleucilla magna Klautau et al., 2004 (Porifera: Calcarea) in Malta.

The calcareous sponge Paraleucilla magna, first recorded from the Mediterranean in 2001 (southern Tyrrhenian, southern Adriatic and northwest Ionian coasts of Italy), is recorded from Malta (Central Mediterranean) where it was found forming part of the fouling community on small, surface markerbuoys around a fish-farm in Marsaxlokk Bay