The Unique Chemistry of Eastern Mediterranean Water Masses Selects for Distinct Microbial Communities by Depth

The waters of the Eastern Mediterranean are characterized by unique physical and chemical properties within separate water masses occupying different depths. Distinct water masses are present throughout the oceans, which drive thermohaline circulation. These water masses may contain specific microbial assemblages. The goal of this study was to examine the effect of physical and geological phenomena on the microbial community of the Eastern Mediterranean water column. Chemical measurements were combined with phospholipid fatty acid (PLFA) analysis and high-throughput 16S rRNA sequencing to characterize the microbial community in the water column at five sites. We demonstrate that the chemistry and microbial community of the water column were stratified into three distinct water masses. The salinity and nutrient concentrations vary between these water masses. Nutrient concentrations increased with depth, and salinity was highest in the intermediate water mass. Our PLFA analysis indicated different lipid classes were abundant in each water mass, suggesting that distinct groups of microbes inhabit these water masses. 16S rRNA gene sequencing confirmed the presence of distinct microbial communities in each water mass. Taxa involved in autotrophic nitrogen cycling were enriched in the intermediate water mass suggesting that microbes in this water mass may be important to the nitrogen cycle of the Eastern Mediterranean. The Eastern Mediterranean also contains numerous active hydrocarbon seeps. We sampled above the North Alex Mud Volcano, in order to test the effect of these geological features on the microbial community in the adjacent water column. The community in the waters overlaying the mud volcano was distinct from other communities collected at similar depths and was enriched in known hydrocarbon degrading taxa. Our results demonstrate that physical phenomena such stratification as well as geological phenomena such as mud volcanoes strongly affect microbial community structure in the Eastern Mediterranean water column.     

Modelling the presence of anchovy Engraulis encrasicolus in the Aegean Sea during early summer, based on satellite environmental data

Acoustic and satellite environmental data as well as bathymetry data were used to model the presence of anchovy, Engraulis encrasicolus during early summer in the northern Aegean Sea (Eastern Mediterranean). Generalized Additive Models (GAMs) were used for modelling and subsequently applied in a predictive mode to identify those areas in the Greek Seas and the entire Mediterranean basin that could support species’ presence. Model results were evaluated with the estimation of Receiver Operating Characteristic (ROC)-plots as well as qualitatively, based on (a) acoustic data from concurrent studies in certain areas of the northern Aegean Sea that were not included in the estimation of the GAM model and (b) historical acoustic data from the central Aegean and Ionian Seas. Mapping the estimated environmental conditions in the Mediterranean basin indicated areas that generally agree with the known distribution grounds of anchovy, such as the straits of Sicily and coastal waters of Tunisia, areas in the Tyrrhenian Sea, the Adriatic Sea, the Gulf of Lions and the Catalan Sea. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Strontium stratigraphy of the upper Miocene Lithothamnion Limestone in the Majella Mountain,central Italy,and its palaeoenvironmental implications

The ⁸⁷Sr/⁸⁶Sr isotope ratio has been widely used as a physical tool to date and correlate carbonate successions due to the long Sr residence time in comparison with the ocean mixing time. If this method works on oceanic successions, marginal basins may show different Sr isotope records in comparison with the coeval ocean one due to sea‐level variations, continental run‐off and restricted water exchanges. In this work, we present the ⁸⁷Sr/⁸⁶Sr isotope record of the upper Miocene carbonate ramp of the Lithothamnion Limestone (Majella Mountain, central Apennines), as an example of the onset of restricted water exchanges between a marginal basin and the ocean water masses. The overall latemost Tortonian–early Messinian Sr isotope record of the Lithothamnion Limestone fits below the global reference line. This deviation has been interpreted as due to the strong control that freshwater input and enhanced continental run‐off, linked to the migration of the Apennine accretionary wedge and foredeep system, have had on the central Adriatic water chemistry. These results imply that an accurate oceanographic and geodynamic framework along with diagenetic overprint investigation has to be taken into consideration prior to apply SIS on carbonate successions on marginal basins, even when facies analyses indicate fully marine conditions. This seems to be the case for the upper Miocene Central Mediterranean carbonate successions, but may have more general validity and be extended to other recent or past marginal basins.     

Mitochondrial DNA phylogeography reveals the existence of an Evolutionarily Significant Unit of the sand goby Pomatoschistus minutus in the Adriatic (Eastern Mediterranean)

The sand goby Pomatoschistus minutus is a major component of marine shelf and estuarine food webs and an important study organism in behavioural research. Yet, despite the sand goby's significance, its past and present patterns of migration and gene flow are poorly understood. Here we use the mtDNA control region and parts of the flanking tRNA genes of 63 fish from six localities in the Adriatic (Eastern Mediterranean), Western Mediterranean, Atlantic, and North Sea to investigate the phylogeography of this gobiid. Phylogenetic analyses and population genetics statistics reveal the existence of an Evolutionarily Significant Unit, sensu Moritz (1994), in the Adriatic and another in the Western Mediterranean, Atlantic, and North Sea. A possible biogeographical scenario for the separation of the ancestral population is that sand gobies in the Adriatic and Western Mediterranean split between 10,000 and 5000 years ago when due to the rise in sea temperature they migrated northwards and were bisected by the Italian peninsula. A testable prediction of this scenario is that sand gobies from the Western Mediterranean, Adriatic, and Aegean form three reciprocally monophyletic groups which are the descendants of a three-way diversification event.     

The family Xystonellidae (Ciliophora, Tintinnina) in the Adriatic Sea

This paper reports quantitative, horizontal and vertical distributiondata of the 11 species of the family Xystonellidae found inthe Adriatic Sea and in the Strait of Otranto. The samples werecollected in coastal and open waters, with a plankton net equippedwith a closing system, in the period from 1973 to 1986. At thedeeper stations of the South Adriatic Pit, hauls were takenin eight vertical layers, while at other stations sampling dependedon the respective depth of each station. Xystonellidae are oceanictintinnines, mainly present in the South Adriatic and the Straitof Otranto throughout the year. They are characteristic of SouthAdriatic and Eastern Mediterranean water masses. Horizontaldistribution of lower mesopelagic species is limited by the200 m isobath. Only sparse individuals of the upper mesopelagicand epipelagic species were found in the Jabuka Pit, probablydue to the late autumn and winter current. These species werenot registered to the north of this region. They were registeredbelow the 200 m depth as dominant tintinnines, while in summerthey represented an average of 81% of the total tintinnine population.     

Mitochondrial DNA phylogeography reveals the existence of an Evolutionarily Significant Unit of the sand goby Pomatoschistus minutus in the Adriatic (Eastern Mediterranean)

The sand goby Pomatoschistus minutus is a major component of marine shelf and estuarine food webs and an important study organism in behavioural research. Yet, despite the sand goby’s significance, its past and present patterns of migration and gene flow are poorly understood. Here we use the mtDNA control region and parts of the flanking tRNA genes of 63 fish from six localities in the Adriatic (Eastern Mediterranean), Western Mediterranean, Atlantic, and North Sea to investigate the phylogeography of this gobiid. Phylogenetic analyses and population genetics statistics reveal the existence of an Evolutionarily Significant Unit, sensu Moritz (1994), in the Adriatic and another in the Western Mediterranean, Atlantic, and North Sea. A possible biogeographical scenario for the separation of the ancestral population is that sand gobies in the Adriatic and Western Mediterranean split between 10,000 and 5000 years ago when due to the rise in sea temperature they migrated northwards and were bisected by the Italian peninsula. A testable prediction of this scenario is that sand gobies from the Western Mediterranean, Adriatic, and Aegean form three reciprocally monophyletic groups which are the descendants of a three-way diversification event.     

Palaeoceanographic record of the last deglaciation in the Strait of Sicily

The palaeoceanographic evolution of the Levantine waters during the last deglacial time is investigated using the sedimentary record of a deep sea core, CS 70-5, from the Linosa basin (35° 44.4′N/13° 11.0′E, 1486 m water depth). Radiocarbon dating and oxygen isotope stratigraphy based on¹⁸O changes inGlobigerina bulloides allow us to recognize and to date the different steps of the deglaciation. These steps are synchronous with those reported in the North Atlantic, but correspond to a δ¹⁸O decrease of higher amplitude than in the Alboran sea or in the North Atlantic Ocean. Major faunal events permit the establishment of a local biozonation which differs from those reported either for the Alboran sea or the Eastern Mediterranean basin. Major breaks in the faunal assemblages occurred during Termination I_A, within the first step of the deglaciation around 14 kyr B.P., and near 10.6 kyr B.P. within the Younger Dryas. The onset of the last deglaciation induced important changes in the characteristics of the Levantine and Atlantic water masses which occupied the Strait of Sicily. The δ¹³C records ofGlobigerina bulloides andCibicidoides pachyderma indicate that the modifications observed in the assemblages of deep faunas are controlled by the oxygenation of the water column. δ¹³C records ofGlobigerina bulloides are similar throughout the West Mediterranean as well as in sediments located below the present Mediterranean outflow. The distributional pattern as well as its δ¹³C record suggest that this species could be a good recorder of the upper Levantine waters and, more precisely, of the mixing layer of the overlying Atlantic waters with the Levantine ones.Major influxes of Atlantic waters during Terminations I_A and I_B could have slowed down the vertical mixing of the different water layers present in the Strait of Sicily and caused a decrease in the oxygenation of the water column. During Termination I_B the effect of Atlantic influxes was reinforced by the occurrence of a low salinity layer in the eastern basin which led to the stagnation of the deep waters. The two episodes of decreased oxygenation in the Levantine waters also favored the precipitation of inorganic magnesium calcite.     

Nile water as a cause of Eastern Mediterranean sapropel formation: Evidence for and against

During the late Pleistocene, sapropels (layers of organic-carbon rich sediment) formed throughout the entire Eastern Mediterranean Basin in close association with glacial/interglacial transitions. The current theory for the mechanism of sapropel formation involves a density stratification of the water column, due to the invasion of a large quantity of low-saline water, which resulted in oxygen depletion of the bottom waters. Most workers believe that this low-salinity water was glacial meltwater that entered the Mediterranean via the Black Sea and a series of interconnected glacial lakes, but the suggestion also has been made that the freshwater originated from the Nile River. In this study the oxygen isotope values of planktonic foraminifera,Globigerinoides ruber, have been examined in six gravity cores and one piston core from the southern Levantine Basin, and compared with the oxygen isotope records ofG. ruber from other areas of the Eastern Mediterranean. This study deals mainly with the latest sapropel which was deposited approximately 7000 to 9000 years ago. Results indicate that Nile discharge probably does reduce salinities somewhat in the immediate area surrounding the mouth of the Nile, but this water is rapidly mixed with the highly saline waters of the easternmost Mediterranean.Using a mixing equation and surface water salinity limitations, an approximate oxygen isotope balance of surface waters was calculated for the time of latest sapropel deposition. This calculation shows that neither Nile River discharge nor Black Sea input (nor both together) are large enough to account for the large-scale oxygen isotope depletion associated with latest sapropel deposition in the Eastern Mediterranean. This suggests that part of the isotopic change at Termination I is probably due to increased surface water salinities during the last glacial maximum. In addition, evidence from the timing of sapropel 1 deposition and the dissolved oxygen balance indicates that deposition of the latest sapropel is associated with increased surface water production of biogenic material, as much as three times higher than that of present day.     

Microbial communities in northern Adriatic mucilaginous aggregates: insight into the early phase of aggregate formation

Insight into the initial phase of aggregate formation was provided by comparison between bacterial communities from freshly formed aggregates dominated by the epipelic diatom Cylindrotheca closterium and associated water masses. This study was performed from 2000 to 2006 in the northern Adriatic. The chemotaxonomic structures and physiological conditions were inferred from the fatty acid profiles of the cultured bacterial communities of all implicated components, fresh aggregates, their adjacent waters, oligotrophic high-salinity waters and halocline waters. The results showed similarity between bacterial communities of fresh aggregates and oligotrophic high-salinity water, suggesting their common origin and involvement in the formation of aggregates. In contrast, the origin of the water adjacent to aggregates was different from that of the other components but was similar to the halocline layer and was likely derived from northern Adriatic waters. The presence and activity of heterotrophic bacteria belonging to Alteromonadaceae, which are regularly observed on fresh aggregates, suggest that the early phase of aggregate formation corresponds to an abrupt change of environmental conditions due to the mixing of central and northern Adriatic waters. The initial colonisation of fresh mucilage ascribes to Alteromonas an important ecological function in aggregate community development related to the succession of phytoplankton and heterotrophic bacteria.     

Seasonal variability of copepod abundance in the Balearic region (Western Mediterranean) as an indicator of basin scale hydrological changes

Spatial and temporal changes of the copepod community have been investigated and related to the environmental variability of the Balearic Sea (Western Mediterranean). The period studied spans from 1994 to 1999 during which we analyzed the abundance and structure copepod variability over a cross-shore transect. Results showed a close link between hydrological changes and the variations of copepod abundance. The synchronous variability of copepods and hydrography indicated the rapid response of this zooplankton group to the inflow of cold and warm water masses coming through the study area. Cluster analysis revealed four main copepod assemblages that distinguished the coastal from the oceanic species and those species with different water masses preference. The copepod assemblage composed of Calanus helgolandicus, Clausocalanus arcuicornis, C. pergens, C. paululus, Calocalanus tenuis and Pleuromamma gracilis was associated with cool salty waters, whereas the assemblage formed by Temora stylifera, C. pavo, C. styliremis, Centropages bradyi and Acartia danae was related to warmer less saline Mediterranean waters. Moreover, it is suggested that changes in sea water temperature and salinity are linked to large-scale changes likely occurring at a basin scale, which is reflected in the Western Mediterranean mesoscale hydrographic changes. Therefore, it is stressed that changes in the Balearic copepod community can be used as potential tracers of the western Mediterranean water masses. Guest editors: S. Souissi & G. A. Boxshall Copepoda in the Mediterranean: Papers from the 9th International Conference on Copepoda, Hammamet, Tunisia     

Abyssal food limitation, ecosystem structure and climate change

The abyssal seafloor covers more than 50% of the Earth and is postulated to be both a reservoir of biodiversity and a source of important ecosystem services. We show that ecosystem structure and function in the abyss are strongly modulated by the quantity and quality of detrital food material sinking from the surface ocean. Climate change and human activities (e.g. successful ocean fertilization) will alter patterns of sinking food flux to the deep ocean, substantially impacting the structure, function and biodiversity of abyssal ecosystems. Abyssal ecosystem response thus must be considered in assessments of the environmental impacts of global warming and ocean fertilization.     

The endurance of endemism: the Mediterranean freshwater gobies and their prospects for survival

Gobies (Teleostei: Gobiidae), spawning in fresh waters of the Mediterranean catchment area, are listed, and their diagnostic features and relationships summarized. The species, by zoogeographic category, include (i) Mediterranean: Padogobius martensii (Günther, 1861) and P. nigricans (Canestrini, 1867) from the northern Adriatic and west-central Italy, (ii) West Balkanian: Economidichthys pygmaeus (Holly, 1929) and E. trichonis Economidis & Miller, 1990, and (iii) Ponto-Caspian: Prorerorhinus marmoratus (Pallas, 1811) and Knipowitschia caucasica (Kawrajsky, in Berg, 1916), from the northern Aegean area but otherwise widespread in the Ponto-Caspian region, and the endemic Mediterranean K. punctatissima (Canestrini, 1864) (north-eastern Italy) and K. thessala (Vinciguerra, 1921) (Thessaly). Scenarios for differentiation following the late Miocene Messinian salinity crisis are outlined. The vulnerability of these species is discussed, and their present status reviewed. Populations no longer exist at the precise type localities of E. pygmaeus (Lefkas) and K. thessala (Hasabali spring, Pinios river system). Special features of scientific and cultural interest are noted, and the biological capability for species recovery is assessed.     

Bacterial Diversity in the South Adriatic Sea during a Strong,Deep Winter Convection Year

The South Adriatic Sea is the deepest part of the Adriatic Sea and represents a key area for both the Adriatic Sea and the deep eastern Mediterranean. It has a role in dense water formation for the eastern Mediterranean deep circulation cell, and it represents an entry point for water masses originating from the Ionian Sea. The biodiversity and seasonality of bacterial picoplankton before, during, and after deep winter convection in the oligotrophic South Adriatic waters were assessed by combining comparative 16S rRNA sequence analysis and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). The picoplankton communities reached their maximum abundance in the spring euphotic zone when the maximum value of the chlorophyll a in response to deep winter convection was recorded. The communities were dominated by Bacteria, while Archaea were a minor constituent. A seasonality of bacterial richness and diversity was observed, with minimum values occurring during the winter convection and spring postconvection periods and maximum values occurring under summer stratified conditions. The SAR11 clade was the main constituent of the bacterial communities and reached the maximum abundance in the euphotic zone in spring after the convection episode. Cyanobacteria were the second most abundant group, and their abundance strongly depended on the convection event, when minimal cyanobacterial abundance was observed. In spring and autumn, the euphotic zone was characterized by Bacteroidetes and Gammaproteobacteria. Bacteroidetes clades NS2b, NS4, and NS5 and the gammaproteobacterial SAR86 clade were detected to co-occur with phytoplankton blooms. The SAR324, SAR202, and SAR406 clades were present in the deep layer, exhibiting different seasonal variations in abundance. Overall, our data demonstrate that the abundances of particular bacterial clades and the overall bacterial richness and diversity are greatly impacted by strong winter convection.     

Modelling potential habitat of the invasive ctenophore <Emphasis Type="Italic">Mnemiopsis leidyi</Emphasis> in Aegean Sea

The invasive ctenophore Mnemiopsis leidyi was accidentally introduced into the Black Sea in the early 1980s and it was first sighted in the Aegean Sea (Eastern Mediterranean) in the early 1990s. This article presents a first attempt to develop a predictive spatial model based on M. leidyi presence data and satellite environmental data from the Aegean Sea during early summer, in order to identify those areas in the Greek Seas and the entire Mediterranean basin that could serve as potential habitat for the species. Generalized additive models (GAM) were applied. The final GAM model indicated higher probability of finding M. leidyi present in depths of 65–135 m and sea surface temperature values of 21–25°C. Furthermore, the significant interaction between photosynthetically active radiation (PAR) and sea level anomaly (SLA) indicated a higher probability of M. leidyi presence in low values of PAR and SLA. In the next step, the final GAM was applied in a prediction grid of mean monthly satellite values for June 2004–2006 in order to estimate probability of M. leidyi presence in the Hellenic Seas and the whole Mediterranean basin at a GIS resolution of 4 km. In the Aegean Sea, species potential habitat included areas influenced by the Black Sea Water (e.g. Thracian Sea, Limnos-Imvros plateau), gulfs that are affected by river runoffs, such as the Thermaikos, Strymonikos and Patraikos gulfs, or areas with strong anthropogenic influence such as the Saronikos gulf. Areas with the same environmental conditions as those in Aegean Sea have been indicated in certain spots of the Levantine Sea as well as in coastal waters of Egypt and Libya, although their spatial extent varied largely among years examined. However, the occurrence of conditions that are linked to high probability of M. leidyi presence does not necessarily mean that these areas can support successful reproduction, high population or bloom levels, since these depend on a combination of temperature, salinity, food availability and the abundance of predators. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Viral density and virus-to-bacterium ratio in deep-sea sediments of the Eastern Mediterranean

Viruses are now recognized as a key component in pelagic systems, but their role in marine sediment has yet to be assessed. In this study bacterial and viral densities were determined at nine deep-sea stations selected from three main sites (i.e., the Sporades Basin, the Cretan Sea, and the Ierapetra Trench at depths of 1,232, 1,840, and 4,235 m, respectively) of the Eastern Mediterranean. The three areas were characterized by different phytopigment and biopolymeric carbon concentrations and by changes in the protein and carbohydrate pools. A gradient of increasing trophic conditions was observed from the Sporades Basin (North Aegean) to the Ierapetra Trench (South Aegean). Viral densities (ranging from 1 x 10(9) to 2 x 10(9) viruses ml of sediment(-1)) were significantly correlated to bacterial densities (n = 9, r(2) = 0.647) and reached values up to 3 orders of magnitude higher than those generally reported for the water column. However, the virus-to-bacterium density ratio in deep-sea sediments was about 1 order of magnitude lower (range of 2 to 5, with a modal value of 2.6) than in pelagic environments. Virus density decreased vertically with depth in sediment cores at all stations and was below detection limits at the 10-cm depth of the abyssal sediments of the Ierapetra Trench. Virus density in the sediment apparently reflected a gradient of particle fluxes and trophic conditions, displaying the highest values in the Sporades Basin. The low virus-to-bacterium ratios and their inverse relationship with station depth suggest that the role played by viruses in controlling deep-sea benthic bacterial assemblages and biogeochemical cycles is less relevant than in pelagic systems.     

Distribution of recent planktonic foraminifera in surface sediments of the Mediterranean Sea

The Mediterranean Sea is a partillay isolated ocean where excess evaporation over precipitation results in large east to west gradients in temperature and salinity. Recent planktonic foraminiferal distributions have been examined in 66 surface sediment samples from the Mediterranean Sea. In addition to mapping the frequency distribution of 16 species, the faunal data has been subjected to cluster analysis, factor analysis and species diversity analysis. The clustering of species yields assemblages that are clearly temperature related. A warm assemblage contains both tropical and subtropical elements, while the cool assemblage can be subdivided into cool-subtropical, transitional and polar-subpolar groupings. Factor analysis is used to delineate the geographic distribution of four faunal assemblages. Factor 1 is a tropical-subtropical assemblage dominated by Globigerinoiden ruber. It has its highest values in the warmer eastern basin. Transitional species (Globorotalia inflata and Globigerina bulloides) dominate factor 2 with highest values occurring in the cooler western basin. Factor 3 reflects the distribution of Neogloboquadrina dutertrei and is considered to be salinity dependent. Subpolar species dominate factor 4 (Neoglobuquadrina pachyderma and G. bulloides), with highest values occurring in the northern part of the western basin where cold bottom water is presently being formed. The Shannon-Weiner index of species diversity shows that high diversity exists over much of the western basin and immediately east of the Strait of Sicily. This region is marked by equitable environmental conditions and relatively even distribution of individuals among the species. Conversely, in areas where temperature and salinity values are more extreme, diversity values are lower and the assemblages are dominated by one or two species.     

Nitrogen as a Factor Affecting Algal Growth Potential of an Oligotrophic Coastal Environment of Eastern Mediterranean Sea

Potential nitrogen limitation to chl a production in surface waters of Saronicos Gulf, Aegean Sea was assayed using the alga Pavlova lutheri as the test organism. The oligotrophic and eutrophic water types of this area were compared by in situ and in vitro chl a production estimations. Additions of ammonium alone as well as in combination with complete nutrient enrichment were made to the oligotrophic waters and the algal growth yield was determined and compared with the corresponding yield in unenriched water cultures. The results from routine nutrient analysis and bioassay experimentation support the view that nitrogen has a priority among the factors limiting phytoplankton growth in the Eastern Mediterranean Sea.     

Environmental influences on the spatial distribution of European hake (Merluccius merluccius) and red mullet (Mullus barbatus) in the Mediterranean

Generalised additive models (GAMs) were used to test the hypotheses that red mullet (Mullus barbatus) and hake (Merluccius merluccius) abundances are related to the bathymetry, spatial location and the temperature-based variability of the NE Mediterranean. Data were collected during a 2-year period (1996–1997) of quasi-synoptic sampling using demersal trawl surveys in the northern Aegean Sea. The results of this study supported these hypotheses. It was found that geographic position and sea bottom characteristics influence the temporal distribution patterns of red mullet and hake. Data are presented that reveal species-specific aggregation patterns and an important habitat utilisation of the area. The modelled species’ abundances showed a strongly non-linear dependence on the explanatory covariates. This study, although not directly dealing with spawning, also provided evidence that red mullet and hake demonstrate environmental and bathymetric preferences in the months posterior to spawning. Mean red mullet abundance was consistently highest in areas with warmer bottom waters in the east and west than in the centre, these areas having shallower depths (35–60 m) and bottom temperatures around 19°C. The red mullet appeared to avoid the cold bottom waters (<16°C) of the deeper regions. Results indicated that areas with the highest hake abundances were located in waters of ∼160 m having bottom temperature of ∼16°C and avoided the shallower waters (<70 m) regardless of their bottom temperature. The present findings also suggested that colder bottom waters at all depths were associated with lower-than-average hake abundance. Red mullet and hake preferences for areas with specific bathymetric and ocean environmental conditions are believed to be linked to the oceanography of the NE Mediterranean ecosystem.     

Occurrence of Diopatra marocensis (Annelida,Onuphidae) in the eastern Mediterranean

The present study deals with the presence of Diopatra marocensis in the eastern Mediterranean. This species is small-sized and inhabited muddy bottom near the opening of rivers or lagoons [salinity range: 33−39‰] in the Aegean and Levantine Seas, and reached a maximum density of 90 ind.m^-2 in Mersin Bay. This species might be an alien species that was introduced from the East Atlantic (near Gibraltar) to the eastern Mediterranean via ballast water of ships, as it has never been reported from the western Mediterranean Sea.