A bathymetric transect in the north coast of Crete first studied in 1989, was revisited 24 years later. Identical sampling design, season, techniques and protocols were followed in both studies in order to minimize bias in the long-term comparisons. This comprehensive macrofaunal dataset (4 stations, 2 sampling seasons, 7 replicates in each study) revealed changes in benthic diversity and community composition between the sampling periods. The recorded changes were higher at the stations located close to the coastal zone. In addition, while benthic communities showed lower total abundance during the recent sampling period, species abundances were more evenly distributed indicating that some species dominated the historical communities. In spite of these changes, the ecological status remained above the threshold values for good ecological status. The results indicated that changes in the benthic community seem to have been driven by local anthropogenic factors and natural variability rather than by large-scale factors such as nutrients influxes in the entire Mediterranean Basin.

The distribution of total and dissolved forms of DMSP and total DMSO was surveyed during two sampling cruises conducted in September 2003 and July 2004 in the North Aegean Sea. During the first cruise the surface concentrations of DMSPt, DMSPd and DMSOt in the coastal group of stations ranged from 20.92 to 23.71 nM, 15.46 to 15.53 nM and 14.90 to 18.73 nM respectively, while in the offshore group the mean concentrations were 27.41 nM (DMSPt) and 14.66 nM (DMSOt). Concerning the phytoplankton assemblage it was dominated by dinoflagellates. During the second cruise, the surface DMSPt, DMSPd and DMSOt concentrations in the coastal group were not significantly changed compared to the first cruise, while the offshore group presented more elevated values (DMSPt: 33.52 nM; DMSPd: 18.78 nM; DMSOt: 36.49 nM). Interestingly the vertical distribution and the phytoplankton abundance in this cruise were changed, with diatoms being the dominant group in the study area. On both cruises statistically significant correlations between small-sized dinoflagellates (≤ 20 μm) as well as coccolithophores and the concentrations of DMSx compounds obtained, suggesting the importance of the above phytoplankton groups in the production and distribution of the these sulphonic forms. At the same time, no significant correlations were observed between DMSx and diatom species. The strong correlation of DMSx species with the group of dinoflagellates coupled with their decorrelation with Chl-a may serve as indirect evidence of heterotrophic forms dominating dinoflagellate taxa thriving in the area during the stratified period.

The present work reports on recent biodiversity records of Mediterranean native species such as Olindias phosphorica in the Turkish Aegean Sea and extended distribution of eleven alien species in the Mediterranean. These are: Bursatella leachi (Mollusca, Gastropoda: Algeria); Callinectes sapidus (Crustacea, Decapoda: Greek Ionian Sea); Caprella scaura (Crustacea, Amphipoda: Mar Piccolo of Taranto); Fistularia commersonii (Fish: Saronikos Gulf, Aegean Sea); Sphoeroides pachygaster (Fish: South Turkey); Musculista perfragilis (Mollusca, Bivalvia: South Turkey); Sepioteuthis lessoniana (Mollusca, Cephalopoda: central eastern coast of Tunisia); Flabellina rubrolineata (Mollusca, opisthobranchia: central Aegean, Greece); Hesionura serrata (Polychaeta: Apulian coast); Stephanolepis diaspros (Fish: Saronikos Gulf, Aegean Sea); and Parvocalanus crassirostris (Crustacea, Copepoda: Lesvos Island, Greek Aegean Sea).

Near-bottom zooplankton sampled by a newly developed hyperbenthic sledge (TTSS2) on the continental shelf (50-200 m) and upper slope (300 m) of Heraklion Bay (Crete, Eastern Mediterranean) consisted of both meso- and macro-zooplankton. Meso-zooplankton was composed mainly of calanoid copepods and crustacean larvae, while macro-zooplankton consisted almost exclusively of chaetognaths. Results revealed that near-bottom zooplankton is found in very high densities close to the seabed and especially on or just a few centimetres above the sediment surface. Furthermore, near-bottom zooplankton abundance was significantly higher during the night than during the day implying that the performance of "reversed" diel vertical migration by these animals is probably due to the presence of predators that use tactile stimuli, rather than vision, to locate prey.

Recent online initiatives in sharing marine biological data, such as the European Regis- ter of Marine Species (ERMS) and the Ocean Biogeographic Information System (OBIS), identified gaps in data from the eastern Mediterranean and Black Sea. Such data are now being collected, for- matted and disseminated by MedOBIS (the Mediterranean Ocean Biogeographic Information Sys- tem) initiative involving Greece, the Ukraine and Israel (test version available at: www.medobis.org). The aim is to develop a taxon-based biogeography database and online data server with links to sur- vey and satellite environmental data. MedOBIS is currently undergoing 4 stages of development, namely, data assembly, formatting, analysis and dissemination. The primary features of the MedOBIS application are its offline GIS (Geographic Information Systems) data formatting capabilities and its online Java- and JavaScript-enabling data server with taxon-based search, mapping and data down- loading capabilities. It is an independent source of biological and environmental data, as well as an online GIS tool designed to facilitate access to historical and current data by marine researchers. As more data become available and are inserted into the system, MedOBIS will function as the eastern Mediterranean and Black Sea node of EurOBIS (the European node of the international OBIS initia- tive, part of the 'Census of Marine Life').

Although the benthopelagic fish species are a focus of commercial exploitation, relatively little attention has been paid to the small-sized invertebrates (0.5-20 mm) living on or very close to the seabed, thus inhabiting the same biotope, known also as hyperbenthos. Recently, interest in this faunal group has increased, as many demersal fish and epibenthic crustaceans have been found to feed on hyperbenthic animals for at least part of their lives. Otter trawls, the most common gear used for demersal fishing, result in significant disturbance of the sediment-water inter-face. Animals that are disturbed by the passage of a trawl may become more available to predators and scavengers. We have been unable to find any reports of studies of the impacts of towed fishing gears, including otter trawls, on hyperbenthos. We studied these effects on the Mediterranean continental shelf in Heraklion Bay (Cretan Sea) using a novel apparatus to simulate the contact of otter trawl groundrope with the seabed. A modified three-level hyperbenthic sledge was used for collecting disturbed (groundrope present) and undisturbed (without groundrope) macrofaunal samples at a towing speed typical of the local commercial vessels. Observations were made before and during the trawling season in an area being actively fished. The preliminary results reported here indicate that trawling causes significant changes in the structure of hyperbenthic communities.

The purpose of this paper is to test the performance of rapid biodiversity assessment techniques in the lagoonal environment at the pan-Mediterranean scale. The multivariate techniques can produce patterns of lagoonal biodiversity along the Mediterranean. Additionally, it is shown that the polychaete inventory can preferably be used rather than the aggregation of information at the family level for the purposes of rapid biodiversity assessment. These techniques, however, appear to be weak for the environmental assessment because they cannot detect differences between the naturally disturbed and the anthropogenically impacted lagoons. Both taxonomic distinctness indices are found to be robust in providing meaningful results for rapid biodiversity/environmental assessment when the crustacean inventory and the polychaete and molluscan ones are used for the estimation of the average taxonomic distinctness and of the variation in taxonomic distinctness values, correspondingly. Conversely, information on the distribution of the macrofaunal species to the Mediterranean lagoons appears to be inadequate for the needs of such rapid biodiversity assessment at a regional scale. It is suggested that information on ecological convergence of the macrofaunal species would probably provide biodiversity indices with additional power, at least in the lagoonal environment.

The purpose of this paper is to investigate seascape biodiversity patterns along the Mediterranean and the Black Sea through the study of the benthic polychaete biogeography of the re- gion. A set of non-parametric multivariate analyses and recently developed diversity indices were per- formed on the benthic polychaete inventories of the areas of the Mediterranean and the Black Sea. Both the numbers of species and the multivariate analyses demonstrate a west-east zoogeocline, shown by the decreasing number of species and by the multivariate similarity pattern of the areas. The performance of the 'second-stage' multi-dimensional scaling (MDS) shows, when species information is aggregated to genera, results belonging practically to the same similarity pattern, independent of the similarity coefficients utilized. The same similarity pattern is derived when species information is aggregated to the zoogeographical categories of amphi-Atlantic, Atlanto-Mediterranean, cosmo- politan and endemic species. BIO-ENV analysis reveals a large number of geographic, climatic and trophic variables to be highly correlated with the similarity pattern derived from the various taxo- nomic/zoogeographical categories. The synergy, however, of the environmental variables is best reflected in the case of the endemic Mediterranean species. The latter category is considered as the critical zoogeographic category with respect to providing information on the evolutionary history of the taxon in the region. The application of the average taxonomic distinctness and the variation of taxonomic distinctness indices resulted in a diversity ranking of the areas, which appears to be inde- pendent of the number of species hosted in each area. However, this is not the case for the phylo- genetic diversity (PD) index. Additionally, the former 2 indices indicate that the benthic polychaete species-pool, hosted in the Mediterranean and the Black Sea areas, may well serve as a useful basis for future comparisons in environmental assessment studies. Finally, results from the application of the area-diversity formula show that the equilibrium model can be applicable for the endemic benthic polychaetes of the region: the number of endemic species can be considered as a function of the de- gree of isolation of the area from the source region against the degree of within-area isolated habitats.

This paper provides a critical review of the main issues regarding the scientific principles underlying environmental monitoring of marine aquaculture operations and makes recommendations relevant to the implementation of best practice for the management of aquaculture in Europe. Given that a variety of cultured species and approaches are adopted in Europe, it is not possible, or indeed desirable, to devise prescriptive guidelines. Instead, this paper reviews how science informs monitoring and provides a framework for the development of a monitoring strategy of marine aquaculture operations that is flexible enough to be applicable to a variety of locations, species and situations.Traditionally environmental monitoring has concentrated on a few key physical and chemical variables and organisms. The trend now, however, is towards whole-system environmental assessment (e.g. CEC 2000; Osparcom 1998), including considerations of the assimilative capacity of specific systems and their ability to absorb and dilute perturbations. Against this background this paper addresses the following specific objectives:review of the rationale and scientific principles underlying current environmental monitoring with specific reference to marine aquaculture;evaluation of the links between monitoring and regulatory criteria, specifically consideration of environmental quality objectives and environmental quality standards, and the role of environmental impact assessmentsassessment of the role of codes of best conduct and practice, and environmental management systems in the management of aquaculture operations.The paper concludes by proposing a set of recommendations which will contribute towards the sustainable management of aquaculture operations, through the implementation of a more focused approach to environmental monitoring.

A generic complex ecological model, the European Regional Seas Ecosystem Model (ERSEM), was applied to a shallow lagoon system in the Eastern Mediterranean. Model results depicting the seasonal variation of nutrients and Chl-alpha in the water column, as well as three benthic functional groups (suspended Feeders, deposit feeders, and benthic carnivores), are validated with in situ data. The likely effect of a technical intervention (river input) increasing the freshwater nutrient inputs on ecosystem functioning is also investigated. Detailed annual carbon fluxes and benthic fauna biomasses are calculated, before and after the river input. The importance of external physical/chemical forcing on the pelagic system and its subsequent effect on the benthic system are demonstrated. Model experiments indicate the shift of the ecosystem from nitrate limitation to predator control with external inputs. Model experiments also show a significant increase in the amount of carbon entering the benthic system through the activity of filter Feeders when river inputs are implemented. (C) 2000 International Council for the Exploration of the Sea.

Gialova Lagoon, a coastal marine ecosystem in the Ionian Sea, suffered the impact of an oil spill incident in October 1993, leading to the extensive fish deaths when the oil tanker ''Iliad'' hit bottom in the entrance of the neighbouring Navarino Bay.A multidisciplinary study investigating the structure and functioning of Gialova Lagoon for the development of an integrated economic, social, and environmental management policy consistent with its conservation was carried out on a seasonal basis during 1995/1996.One of the research priorities was to investigate the structure and dynamics of the macrozoobenthic communities and assess whether these communities had recovered from the impact of the oil spill.The various methods applied (abundance/ biomass comparison, distribution of species in geometric abundance and geometric size classes) revealed no detectable disturbance of the macrobenthic communities due to anthropogenic impact.However, it was proved that the lagoonal macrofauna suffered extreme natural disturbance due to a dystrophic crisis that occurred during autumn although they successfully recovered in subsequent seasons.Different sets of environmental factors were found to be highly correlated with the temporal and spatial distribution pattern of the macrobenthic communities and are discussed in detail.The coenocline observed in Gialova Lagoon appears to be strongly correlated with the degree of water exchange with adjacent marine and continental environments.

The annelid community of a shallow Mediterranean lagoon (Gialova Lagoon, Ionian Sea) was studied on a seasonal basis. Out of the 39 species identified eight are reported for the first time from the central Mediterranean. The dominant species were the polychaetes Capitella capitata , Neodexiospira pseudocorrugata , Malacoceros fuliginosus , Perinereis cultrifera , Hediste diversicolor , Heteromastus filiformis and the oligochaete Limnodriloides maslinicensis . Uni- and multivariate methods were employed to study the community structure. The coenocline observed is strongly related to the degree of isolation; its main features (i.e. number of species, density, geometric abundance and size-classes) in space and time are presented and discussed in detail. The distribution pattern of the annelid community has been found to be governed by a different set of environmental factors in each season. Although this narrow lagoonal habitat suffers severe dystrophic episodes it manages to recover, demonstrating a seasonal community pattern.

Sediment characteristics determining macrofauna communities were investigated on the continental shelf of Crete. The sedimentary environment of the outer continental shelf of Crete is characterized by a silty substrate with significant decrease in chlorophyll a and organic carbon concentration with depth. Redox potential values indicated an ample supply of oxygen at all depths. Values of most production-related parameters (TOC, chlorophyll a, ATP) were found at the low end of the range reported from the literature even though the sampling stations were very close to the coastline. Organic carbon to chlorophyll ratios in the sediments indicated that most of the organic material is of phytoplankton origin; the quality of the organic material in the outer shelf, however, seems to be of lower bioavailability.

The analysis of 99 quantitative macrobenthic samples taken from the Cretan shelf at depths ranging from 40 to 190 m yielded 547 species from a total of 18858 individuals. Both average abundance and biomass decreased with depth in this zone by 85 and 75 % respectively The fauna was not consistently related to the biocoenoses proposed for the Mediterranean, at least with regard to the distribution of characteristic species in the sampled stations. Diversity also decreased with depth, resulting in a rather impoverished fauna towards the outer shelf. The main factors explaining the overall macrofaunal distribution were depth and chlorophyll a, while further analysis for the 4 different groups of stations identified by cluster analysis revealed that factors controlling the structure of the assemblages also change with depth: in the shallow stations sedimentary characteristics such as grain size play an important role while in deep offshore stations macrofauna is largely shaped by food availability and the quality of sedimenting phytoplankton biomass.

The feeding habits of the striped red mullet, Mullus surmuletus on the Cretan shelf (north-eastern Mediterranean), in respect to season and fish size, were examined. Stomach contents of 446 specimens, 62–230 mm TL, collected by demersal trawl from August 1988 to August 1989, were analyzed. Feeding intensity was high throughout the study period and varied significantly among the size classes. Crustaceans (amphipods and decapods) predominated M. surmuletus diet. The composition of the prey ingested varied with predator size fish and cephalopods occurred exclusively in the diet of specimens larger than 161 mm TL. The mean weight of stomach contents increased significantly for fish larger than 171 mm TL, while the mean number of prey items did not differ among the size classes. Diets varied seasonally; decapods were more important in summer, whereas amphipods were more important during winter and spring. The results indicated that the red striped mullet fed on a narrow range of prey items and could be considered a specialist. The morphological characteristics and the foraging behaviour of M. surmuletus account for both prey type selection and the feeding patterns observed.