A review on the biodiversity of hard substrate invertebrate communities in the Aegean Sea

This review attempts to estimate the biodiversity of the macrobenthic communities that develop on hard bottoms in the Aegean Sea. Literature analysis revealed that 1,171 species inhabit the hard substrate communities, constituting 20.9% of the total Mediterranean species. The hierarchical cluster analysis of the available data identified five major types: (1) the supralittoral communities, (2) the midlittoral communities, (3) the port communities, (4) the various facies of the photophilic algae community, and (5) the facies of the sciaphilic algae community. Thus, hard bottom communities in the Aegean seem to be separated mainly according to vertical zonation. A total of 68 hard-bottom species are under multiple exploitation, providing considerable economic profit. Taking into account the structural complexity of hard substrate benthic communities and their sensitivity to disturbances, it is essential to preserve the biodiversity of these biotopes

Structure of the artificial hard substrate assemblages in ports in Thermaikos Gulf (North Aegean Sea)

The present study describes the hard substrate assemblages established on the concrete blocks of three ports placed in gradually longer distances from the main source of pollution in Thermaikos Gulf. The samplings were performed on a seasonal basis for a 2-year period. The data analysis indicates a clear separation of the assemblages from each port. Evenness and Shannon-Weaver diversity indices were calculated and their values were found to be quite high. This fact, combined with the seasonal pattern that these assemblages hold, reveals stability and a good adaptation of their faunistic components to local environmental conditions. A change due to the construction of a new block functioning as a surge barrier was detectable at the station of N. Michaniona. Once again, biomonitoring proves to be essential in order to obtain useful information about the water conditions. Emphasis was laid on the taxa of Polychaeta by analyzing their numerical abundance and their feeding guilds separately. The results were very similar, a fact that supports the opinion that a specific taxonomic group can be used for the description and the monitoring in many different cases.Ce travail décrit les assemblages de substrats durs qui se sont établis sur des blocs dans trois ports de plus en plus éloignés des sources de pollution dans le golfe de Thermaikos. Des prélèvements saisonniers durant deux années montrent une séparation nette des assemblages des trois ports. Les indices de diversité (Shannon–Weaver) et d’équitabilité sont plutôt élevés. Ce fait, ainsi que le schéma saisonnier, révèlent une stabilité et une bonne adaptation de la faune à son environnement. Un changement dû à la construction d’un nouveau bloc établi pour barrer la houle est détectable à la station du port N Michaniona. Une fois de plus, le suivi biologique paraît essentiel pour obtenir des informations utiles sur les conditions environnementales. L’accent est mis sur les taxons de polychètes en mesurant l’abondance des différentes guildes trophiques. Les résultats sont voisins, ce qui prouverait qu’un groupe taxinomique spécifique peut être utilisé pour décrire et suivre l’évolution dans pas mal de cas

Polychaetes associated with the sciaphilic alga community in the northern Aegean Sea: Spatial and temporal variability

Polychaete biodiversity has received little attention despite its importance in biomonitoring. This study describes polychaete diversity, and its spatial and temporal variability in infralittoral, hard substrate assemblages. Seven stations were chosen in the central area of the northern Aegean Sea. At each station, one to three depth levels were set (15, 30 and 40 m). Five replicates were collected by scuba diving with a quadrat sampler (400 cm2) from each station and depth level during summer for the spatial analysis, and seasonally for the study of temporal changes. Common biocoenotic methods were employed (estimation of numerical abundance, mean dominance, frequency, Margalef's richness, Shannon-Weaver index and Pielou's evenness). A total of 5,494 individuals, belonging to 79 species, were counted and classified. Diversity indices were always high. Clustering and multidimensional scaling techniques indicated a high heterogeneity of the stations, although these were all characterized by the sciaphilic alga community. A clear seasonal pattern was not detectable. Summer and autumn samples discriminate, while winter and spring form an even group. The abundance/biomass comparison indicated a dominance of k-strategy patterns, characteristic of stable communities. © Springer-Verlag and AWI 2004

Redescription of the Mediterranean endemic sea-pen Crassophyllum thessalonicae (Octocorallia: Pteroeididae)

Five colonies of the rare pennatulacean Crassophyllum thessalonicae were recently collected from Thermaikos Gulf (north-east Mediterranean), which allowed a study of their biometry; accordingly, new features are added to the original description of the species. Based on these data the morphological characters that distinguish C. thessalonicae from its congeners are reviewed. © 2011 Marine Biological Association of the United Kingdom