Chryssanthi Antoniadou

Data integration for European marine biodiversity research: creating a database on benthos and plankton to study large-scale patterns and long-term changes.

The general aim of setting up a central database on benthos and plankton was to integrate long-, medium- and short-term datasets on marine biodiversity. Such a database makes it possible to analyse species assemblages and their changes on spatial and temporal scales across Europe. Data collation lasted from early 2007 until August 2008, during which 67 datasets were collected covering three divergent habitats (rocky shores, soft bottoms and the pelagic environment). The database contains a total of 4,525 distinct taxa, 17,117 unique sampling locations and over 45,500 collected samples, representing almost 542,000 distribution records. The database geographically covers the North Sea (221,452 distribution records), the North-East Atlantic (98,796 distribution records) and furthermore the Baltic Sea, the Arctic and the Mediterranean. Data from 1858 to 2008 are presented in the database, with the longest time-series from the Baltic Sea soft bottom benthos. Each delivered dataset was subjected to certain quality control procedures, especially on the level of taxonomy. The standardisation procedure enables pan-European analyses without the hazard of taxonomic artefacts resulting from different determination skills. A case study on rocky shore and pelagic data in different geographical regions shows a general overestimation of biodiversity when making use of data before quality control compared to the same estimations after quality control. These results prove that the contribution of a misspelled name or the use of an obsolete synonym is comparable to the introduction of a rare species, having adverse effects on further diversity calculations. The quality checked data source is now ready to test geographical and temporal hypotheses on a large scale.

Peracarida populations of hard substrate assemblages in ports of the NW Aegean Sea (eastern Mediterranean)

This study deals with the structure of Peracarida populations in four ports in the NW Aegean Sea, Greece, and with the degree this structure is influenced by the particular biotic and abiotic conditions that prevail in the ports. Quantitative samples were taken during summer and winter in two successive years from artificial hard substrates and were analysed using common biocoenotic methods. The examination of approximately 81,250 specimens revealed the presence of 24 Peracarida species, the most dominant of which were Corophium acutum, Leptochelia savignyi and Elasmopus rapax. All species are very common and have been reported from many sites and assemblages in the N Aegean Sea. The ratios of certain Peracarida genera are discussed as possible indicators of environmental health that may be used in long-term biomonitoring programmes on the impact of pollution in harbours.

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

Abstract 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.

Macrofauna biodiversity of mussel bed assemblages in Thermaikos Gulf (northern Aegean Sea)

Biomonitoring of mussel bed assemblages can provide valuable information about the impact of pollution on hard substrate assemblages. This study of Mytilus galloprovincialis mussel beds in Thermaikos Gulf (northern Aegean Sea) deals with the spatial and temporal structure of the associated fauna. Samples were collected and abiotic factors were measured in two successive years. Common biocoenotic methods were employed to analyze the data. The samples could be separated into three groups, with summer and winter samples being clearly different. A total of 100 species were found: polychaetes and crustaceans were the most dominant taxa. The assemblage shows high diversity with respect to species abundance. Biotic interactions within the assemblage appear to influence its composition, although the total evenness remains unaffected in space and time. The M. galloprovincialis assemblages can be found in clean as well as in polluted waters and, therefore, are of great interest in biomonitoring studies.

Zoobenthos associated with the invasive red alga Womersleyella setacea (Rhodomelacea) in the northern Aegean Sea

The spatial and temporal structure of the zoobenthos associated with the invasive red alga Womersleyella setacea was studied in the northern Aegean Sea, Greece. Five replicate quadrats (20x20 cm) were collected, seasonally from July 1997 to August 1998, by SCUBA diving at four sites and two depth levels (15 and 30 m) in the Chalkidiki Peninsula. We collected 23,090 specimens representing 278 animal species. Multivariate analysis showed mainly spatial differences in community structure, while the temporal ones were minimal. The ordination of sites showed a clear zonation pattern according to the different algal forms that cover the rocky substrate, with inclination the only environmental factor involved. The epifauna associated with the invasive alga was differently structured compared with three native seaweeds, showing increased species richness and abundance. The filamentous alga W. setacea was dominant in all seasons and depth levels, creating a stable habitat that contributed to the loss of seasonality in zoobenthic community structure.

Aegean Bath Sponges: Historical Data and Current Status

This study attempts to evaluate the status of the populations of bath sponges (species of the genera Spongia and Hippospongia) in the Aegean, combining historical sources dated before a series of disease outbreaks that occurred from 1986 on, unpublished data obtained during the recovery phase after the first incident, as well as a current survey of the main spongiferous beds in the area. The latter was implemented through an extensive sampling trip assisted by professional sponge fishermen, including 55 stations distributed in 17 Aegean islands. Our analysis of population and morphometric data exhibits regeneration potential for bath sponge stocks, yet highlights the contrast between their present status and that of historical times. Uniformity is not evident, as several populations retain high abundances, while simultaneously areas purportedly rich in bath sponges appear deprived. Small-scale environmental regimes in the Aegean are proposed as the shaping factors of this situation; however, the importance of additional elaborate studies and the implementation of an effective regulation scheme regarding their fisheries are stressed.

Sponges of economical interest in the Eastern Mediterranean: an assessment of diversity and population density

The aim of this paper was to investigate diversity and population density of sponges with manifest or potential economical interest for the first time in the Eastern Mediterranean. For this purpose, the area of Dodecanese, an Aegean area traditionally harvested for sponges was surveyed for bath sponges and species known as sources of bioactive compounds. Twenty stations of diverse orientation, substrate inclination and type of substratum, located on seven islands, were surveyed and totally 36 demosponge species were found. The data, collected with a non‐destructive method, were subjected to multivariate analysis which showed that sponge diversity was higher in areas with vertical cliffs. A considerable spatial variation was revealed by the formation of two groups of stations, according to sponge species presence/absence: one including vertical cliffs and a second one, including moderately inclined cliffs, Posidonia meadows and detritic biogenic bottoms. Bath sponges occurred at a restricted number of stations and although in relatively low population densities, they revealed a sign of recovery after the devastating epidemic events. Higher stock availability was found for six biotechnologically promising species which were distributed all over the study area. The above results are encouraging for a future sustainable stock exploitation and open a new perspective for sponge mariculture in the area.

Population dynamics, allometric relationships and reproductive status of Microcosmus sabatieri (Tunicata: Ascidiacea) in the Aegean Sea

The Mediterranean ascidian Microcosmus sabatieri is among the conspicuous benthic invertebrates, forming dense populations on moderately inclined cliffs. It is an edible species, commercially harvested at the southern part of the Aegean Sea. Considering that the biology of this species has not been adequately studied, a three-year survey was carried out focusing on population structure, allometric relationships and reproductive status of M. sabatieri stocks in Astypalea Island (Dodecanese, south Aegean). Population density showed insignificant temporal variation and lower values at the steeper station, while the pattern of dispersion was random. All measured biometric characters showed high plasticity, especially those related to siphons. All the examined morphometric relationships follow negative allometry. Ascidian length was a good predictor of biomass, and a strong relation was observed between mantle and tunic characters. Gonad somatic index showed a single spawning season per year, in winter. Length-frequency distribution analysis revealed the presence of one mode of medium sized individuals, implying that M. sabatieri stocks are under moderate fishing pressure in the study area.

Population dynamics and reproductive status of Microcosmus savignyi Monniot, 1962 (Thermaikos Gulf, Eastern Mediterranean): a preliminary assessment

The ascidian Microcosmus savignyi, a suspension‐feeding species, is among the prominent biota of hard substratum benthic communities in Thermaikos Gulf, showing increased population density on biogenic substrata. Considering that the biology of this species is not adequately studied, a one‐year study was carried out to provide information on population structure, growth parameters and reproductive status of M. savignyi stocks in Thessaloniki Bay. Population density showed a steady seasonal trend. Microcosmus savignyi experienced faster axonometric growth and reaches the maximum asymptotic length slowly, having a life span over one year. Length‐frequency distributions analysis revealed the presence of two cohorts. Gonad‐somatic index and gonad histology showed that the species is a protandrous hermaphrodite, with an expanded spawning season, lasting from the end of summer, when the release of spermatozoa begins, to the end of winter, when the release of oocytes is completed. The ecological implications of this reproductive mode are not well understood, however they may prevent self‐fertilization, increasing the fitness of the population to its environment.

Small-scale spatial variability of zoobenthic communities in a commercial Mediterranean port

In the context of the limited information on the ecology of port communities, the present work aims at assessing the small-scale spatial variability of zoobenthos inhabiting hard and soft substrata, in a Mediterranean port with high levels of commercial shipment. Samples were collected in summer from three stations and four depth levels, using core and quadrate samplers. A total of 34,578 individuals were collected, identified to 118 animal species. Soft substratum communities were impoverished and their structure varied spatially according to sediment composition. At a functional level deposit feeders dominated; their abundance decreased at the silty sites. Biotic indices were found inadequate for the assessment of ecological quality, due to the very low abundance of the fauna. Fouling communities varied spatially in vertical scales; diversity indices and the abundance of Bivalvia varied also in horizontal scales. Suspension and deposit feeders dominated showing a decreasing trend with depth. Two animal-dominated communities, serpulid blocks in the lower midlittoral zone and mussel beds in the sublittoral, substituted an algal-dominated community, which has been previously recorded from the same port quays. This substitution may be due to the intensive mussel farming in the nearby area contributing to the rapid expansion of mussels and of their serpulid biofoulers. Despite the existence of biogenic substrata, which enhance habitat complexity, the diversity of the associated fauna decreased and most species were tolerant to organic pollution. Recursive biomonitoring seems necessary to assess the ecological status of communities and to develop integrated management plans for temperate ports.