Mediterranean Coastal System Research Articles

Geochemical, mineralogical records, and statistical approaches in establishing sedimentary in the environment of a Mediterranean coastal system: case of Sebkha El-Guettiate (southeastern Tunisia).

The current study was conducted within the context of the Holocene era in Sebkha El-Guettiate, located in southeastern Tunisia. The aim was to determine the factors influencing the geochemical and mineralogical composition of sediments and to elucidate the sedimentary characteristics of the Holocene within the Sebkha core. We examined a sediment core extending 100cm from this Sebkha, subjecting it to comprehensive analysis to uncover its sedimentological, mineralogical, and geochemical properties. Several techniques were employed to strengthen and validate the connections between geochemical and mineralogical analyses, including X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and infrared (IR) spectroscopy, among others. Furthermore, statistical analyses utilizing principal component analysis (PCA) were applied to the results of the geochemical and mineralogical studies, aiding in the identification of patterns and relationships. A comprehensive mineralogical assessment of the core's sediments revealed the presence and interpretation of carbonate minerals, evaporite minerals, and detrital minerals. Through the application of infrared (IR) spectrometer techniques to all sediment samples, we gained insight into the mineralogical components and the distribution of key elements such as quartz, kaolinite, calcite, feldspar, and organic carbon. The geochemical composition demonstrated a clear dominance of silica (SiO2), accompanied by fluctuations in carbonate percentages (CaCO3). The prominent major elements, primarily magnesium (Mg) and calcium (Ca) originating from dolomitization, sodium (Na) and chlorine (Cl) from halite, and calcium (Ca) from gypsum, exhibited varying levels. Results from Rock-Eval 6 pyrolysis indicated that the organic matter within the sediments is generally a mixture of terrestrial and aquatic origins. This study provides practical information that underscores the diverse origins contributing to Sebkha sediment formation, often influenced by saline systems.

Phytoplankton community as monitoring tool in the terminal stretch of a micro-tidal estuary facing the Tyrrhenian Sea

Mediterranean coastal systems, particularly those characterized by river mouths, have played an important role in the history of human civilization, thanks to unique species assemblages, a high biodiversity, and complex ecological interactions. The overlapping of multiple cross-scale effects, triggered by the ongoing climate change, makes these systems particularly important sites for ecological studies. Here, we have investigated the phytoplankton community structure in the terminal stretch of the Sele River (Tyrrhenian Sea) under two different hydrological regimes: i) with river mouth occluded by sediments preventing water exchange with the sea; ii) with river mouth completely opened, which allowed the maximum water mass exchanges between the river and the sea. The strong variations in physical-chemical properties of the water column, the point-distribution of total phytoplankton biomass, and the dominance of cryptophytes and cyanophytes under occluded and opened river mouth, respectively, indicate the presence of strong allogenic pressures acting on the system. Our data suggest that the monitoring of phytoplankton communities in the terminal stretch of micro-tidal estuaries, could be a useful tool for studying the extent of climate change underway in Mediterranean coastal marine areas.

Sediment quality and environmental risk assessment in a Mediterranean coastal system using geochemical and multivariate statistical analyses: the case of Boughrara Lagoon (southeastern Tunisia)

Coastal ecosystems are the most vulnerable to natural and anthropogenic pressures which should be assessed using various chemical and ecological indicators. Our study aims to provide practical monitoring of anthropogenic pressures related to metal discharges in coastal waters for identifying potential ecological deterioration. The spatial variability of various chemical elements concentrations and their main sources were determined in the surficial sediments of a Mediterranean coastal area submitted to high anthropogenic pressure, the semi-enclosed Boughrara Lagoon located in southeastern Tunisia, by conducting several geochemical and multi-elemental analyses. The grain size and the geochemical analyses both suggested a marine influence of the sediment inputs in the north of the area (near Ajim channel), whereas continental and aeolian features dominated the sedimentary inputs in the southwestern lagoon. This last area was also characterized by the highest concentrations of metals, in particular Pb (4.45-173.33ppm), Mn (68.45-1469.27ppm), Cu (7.64-134.26ppm), Zn (28.74-244.79ppm), Cd (0.11-2.23ppm), Fe (0.5-4.9%), and Al (0.7-3.2%). By referring to background crustal values and the contamination factor calculations (CF), the lagoon is considered as highly polluted for Cd, Pb, and Fe (3 < CF < 6). Three possible sources of pollution were identified: phosphogypsum effluents (P, Al, Cu, and Cd), the ex-Pb mine (Pb and Zn), and the cliff weathering and streams input from the red clay quarry (Fe). Furthermore, pyrite precipitation was identified for the first time in the Boughrara lagoon, suggesting the occurrence of anoxic conditions in this lagoon.

Environmental Assessment of Potentially Toxic Elements Using Pollution Indices and Data-Driven Modeling in Surface Sediment of the Littoral Shelf of the Mediterranean Sea Coast and Gamasa Estuary, Egypt

Coastal environmental assessment techniques have evolved into one of the most important fields for the long-term development and management of coastal zones. So, the overall aim of the present investigation was to provide effective approaches for making informed decisions about the Gamasa coast sediment quality. Over a two-year investigation, sediment samples were meticulously collected from the Gamasa estuary and littoral shelf. The inductively coupled plasma mass spectra (ICP-MS) was used to the total concentrations of Al, Fe, Ti, Mg, Mn, Cu, P, V, Ba, Cr, Sr, Co, Ni, Zn, Pb, Zr, and Ce. Single elements environmental pollution indices including the geoaccumulation index (Igeo), contamination factor (CF), and enrichment factor (EF), as well as multi-elements pollution indices comprising the potential ecological risk index (RI), degree of contamination (Dc), and pollution load index (PLI) were used to assess the sediment and the various geo-environmental variables affecting the Mediterranean coastal system. Furthermore, the Dc, PLI, and RI were estimated using the random forest (RF) and Back-Propagation Neural Network (BPNN) depending on the selected elements. According to the Dc results, all the investigated sediment samples categories were considerably contaminated. Cr, Co, Ni, Cu, Zr, V, Zn, P, and Mn showed remarkable enrichment in sediment samples and were originated from anthropogenic sources based on the CF, EF, and Igeo data. Moreover, the RI findings revealed that all the samples tested pose a low ecologically risk. Meanwhile, based on PLI, 70% of the Gamasa estuary samples were polluted, while 93.75% of littoral shelf sediment was unpolluted. The BPNNs -PCs-CD-17 model performed the best and demonstrated a better association between exceptional qualities and CD. With R2 values of 1.00 for calibration (Cal.) and 1.00 for validation (Val.). The BPNNs -PCs-PLI-17 models performed the best in terms of measuring PLI with respective R2 values of 1.00 and 0.98 for the Cal. and Val. datasets. The findings showed that the RF and BPNN models may be used to precisely quantify the pollution indices (Dc, PLI, and RI) in calibration (Cal.) and validation (Val.) datasets utilizing potentially toxic elements of surface sediment.

Drivers of Microbial Carbon Fluxes Variability in Two Oligotrophic Mediterranean Coastal Systems

The carbon fluxes between phytoplankton and heterotrophic bacterioplankton were studied in two coastal oligotrophic sites in the NW Mediterranean. Phytoplankton and bacterial production rates were measured under natural conditions using different methods. In the Bay of Villefranche, the temporal variability revealed net heterotrophy in July-October and net autotrophy in December-March. The spatial variability was studied in the Bay of Palma, showing net autotrophic areas in the west and heterotrophic areas in the east. On average bacterial respiration, represented 62% of the total community respiration. Bacterial growth efficiency (BGE) values were significantly higher in autotrophic conditions than in heterotrophic ones. During autotrophic periods, dissolved primary production (DPP) was enough to sustained bacterial metabolism, although it showed a positive correlation with organic carbon stock (DOC). Under heterotrophic conditions, DPP did not sustain bacterial metabolism but bacterial respiration correlated with DPP and bacterial production with DOC. Temperature affected positively, DOC, BGE, bacterial respiration and production when the trophic status was autotrophic. To summarize, the response of bacterial metabolism to temperature and carbon sources depends on the trophic status within these oligotrophic coastal systems.

Trade-offs between sampling effort and data quality in habitat monitoring

The transect method has been widely used to monitor habitat conservation status and has been recently recommended as the best tool to monitor steep ecological gradients, such as those in coastal systems. Despite that, the effectiveness of the transect approach can be limited when considering the sampling effort in terms of time needed for sampling. Our work aimed at evaluating the efficacy of the transect approach in a Mediterranean coastal system. Specifically we aimed at evaluating the sampling effort versus the completeness of datasets obtained by performing belt transects in different ways specifically designed to progressively reduce the sampling effort: (i) sampling plots adjacently (“adjacent-plot transect”); (ii) sampling plots alternately (“alternate-plot transect”); (iii) sampling one plot at each plant community along the vegetation zonation (“zonation-plot transect”). We evaluated method efficiency in terms of number and type of habitats identified, spatial extent, species richness and composition, through multivariate analyses, null models and rarefaction curves. The sampling effort was measured in terms of time needed for sampling. The zonation-plot transect had the lowest sampling effort, but provided only an approximation of the state of the dunal communities. The alternate-plot transect showed the best trade-off between the sampling effort and the completeness of information obtained, and may be considered as a efficient option in very wide coastal systems. Our research provides guidelines that can be used in other coastal systems to choose the most cost-effective monitoring method thereby maximising the efficient use of monitoring resources.

Marine Microphytobenthic Assemblage Shift along a Natural Shallow-Water CO2 Gradient Subjected to Multiple Environmental Stressors

Predicting the effects of anthropogenic CO2 emissions on coastal ecosystems requires an understanding of the responses of algae, since these are a vital functional component of shallow-water habitats. We investigated microphytobenthic assemblages on rock and sandy habitats along a shallow subtidal pCO2 gradient near volcanic seeps in the Mediterranean Sea. Field studies of natural pCO2 gradients help us understand the likely effects of ocean acidification because entire communities are subjected to a realistic suite of environmental stressors such as over-fishing and coastal pollution. Temperature, total alkalinity, salinity, light levels and sediment properties were similar at our study sites. On sand and on rock, benthic diatom abundance and the photosynthetic standing crop of biofilms increased significantly with increasing pCO2. There were also marked shifts in diatom community composition as pCO2 levels increased. Cyanobacterial abundance was only elevated at extremely high levels of pCO2 (&gt;1400 μatm). This is the first demonstration of the tolerance of natural marine benthic microalgae assemblages to elevated CO2 in an ecosystem subjected to multiple environmental stressors. Our observations indicate that Mediterranean coastal systems will alter as pCO2 levels continue to rise, with increased photosynthetic standing crop and taxonomic shifts in microalgal assemblages.

Highly diverse recombining populations of Vibrio cholerae and Vibrio parahaemolyticus in French Mediterranean coastal lagoons.

Vibrio parahaemolyticus and Vibrio cholerae are ubiquitous to estuarine and marine environments. These two species found in Mediterranean coastal systems can induce infections in humans. Environmental isolates of V. cholerae (n = 109) and V. parahaemolyticus (n = 89) sampled at different dates, stations and water salinities were investigated for virulence genes and by a multilocus sequence-based analysis (MLSA). V. cholerae isolates were all ctxA negative and only one isolate of V. parahaemolyticus displayed trh2 gene. Most Sequence Types (ST) corresponded to unique ST isolated at one date or one station. Frequent recombination events were detected among different pathogenic species, V. parahaemolyticus, V. cholerae, Vibrio mimicus, and Vibrio metoecus. Recombination had a major impact on the diversification of lineages. The genetic diversity assessed by the number of ST/strain was higher in low salinity condition for V. parahaemolyticus and V. cholerae whereas the frequency of recombination events in V. cholerae was lower in low salinity condition. Mediterranean coastal lagoon systems housed V. cholerae and V. parahaemolyticus with genetic diversities equivalent to the worldwide diversity described so far. The presence of STs found in human infections as well as the frequency of recombination events in environmental vibrios populations could predict a potential epidemiological risk.

Contamination by trace metals and their trophic transfer to the biota in a Mediterranean coastal system affected by gull guano

Contamination by trace metals and their trophic transfer to the biota in a Mediterranean coastal system affected by gull guano

A case study on the application of the MSFD to Mediterranean coastal systems: the Po plume, as a transitional water system in the Northern Adriatic basin

1 - In the frame of the Marine Strategy Framework Directive (MSFD) of the European Community, in order to assess the Good Environmental Status (GES) of the marine coastal and estuarine waters, the eutrophication descriptors include several aspects of the phytoplankton communities (such as composition, abundance and biomass). 2 - Two oceanographic campaigns were carried out in the area off the Po River plume, where a highly dynamic frontal zone separates an inshore and an offshore system. The coupling of size structure and diagnostic pigments of phytoplankton communities in relation to different environmental contexts are tested as an expedite and informative tool to assess water quality sensu MSFD. 3 - The Po plume creates a very dynamic frontal zone, resulting in strong trophic gradients within a relatively small area. 4 - The spatio-temporal variability of salinity in coastal waters and in transitional waters plays a pivotal role in structuring phytoplankton communities. 5 - The dynamics of forcing factors drive changes in cell-size structure, in the functional group composition as well as a shift in size within the same functional group. 6 - The combination of phytoplankton size-structure and chemotaxonomic compositions is proposed as an expedite tool for investigating, at the appropriate scales, the ecology of transitional water systems.

Effects of a small seagull colony on trophic status and primary production in a Mediterranean coastal system (Marinello ponds, Italy)

Colonies of seabirds have been shown to influence nutrient cycling and primary production of coastal areas, but knowledge is still limited above all for smaller colonies. This study evaluates the influence of a small resident seagull colony (Larus michahellis Naumann, 1840) on a Mediterranean coastal system (Marinello ponds, Sicily, Italy). The presence of ornithogenic organic matter from seagull guano was first assessed at increasing distances from the colony using δ15N to indicate the effects of guano on the trophic status and primary production. The pond directly affected by guano deposition showed an anomalous water and sediment chemistry, especially regarding physico-chemical variables (pH), nitrogen isotopic signature, nutrient balance and phytoplankton biomass. These effects were not observed in the adjacent ponds, highlighting pronounced, small spatial-scale variability. Given the worldwide presence of seabird colonies and the scarcity of research on their effect on coastal marine areas, the study shows that seabird-mediated input may be important in influencing ecosystem dynamics of coastal areas, even where both the system in question and the colony are small.

Effects of Caulerpa racemosa invasion on soft-bottom assemblages in the Western Mediterranean Sea

The present study aimed at evaluating the effects of Caulerpa racemosa var. cylindracea spread on Mediterranean soft-bottom assemblages. The benthic assemblages colonized by C. racemosa were compared with non invaded assemblages at multiple spatial scales. In addition, a manipulative experiment has been conducted over a one-year period in order to compare the structure of native assemblages invaded by the alga with others where the alga has been manually removed and others that were not invaded. Results of both studies showed that Mediterranean soft-bottom assemblages invaded by C. racemosa differed from non invaded ones in terms of species composition, abundance and patterns of spatial variability. Moreover, in areas cleaned out from the alga, the benthic assemblages begin to recover their structure and after one year they get more similar to the assemblages observed in non invaded areas. The present paper, taking into account different aspects of C. racemosa invasion in Mediterranean soft bottoms, highlighted that the observed increase in alpha diversity did not correspond to an increase in the overall diversity of the studied system. Infact, the loss of beta diversity in invaded sites, together with the spread of species typical of vegetated habitats, may contribute to a homogenization of the Mediterranean coastal system. Furthermore, a possible role of ecosystem engineer for C. racemosa can be hypothesized.

Patterns of diversity in rocky subtidal macroalgal assemblages in relation to depth

Abstract One of the peculiarities of subtidal rocky assemblages of the Mediterranean Sea in comparison to other geographical regions is the development of important biogenic structures in deeper habitat that can influence coastal diversity. We compared species composition, alpha diversity, functional diversity and patterns of spatial variability between shallow and deep subtidal macroalgal assemblages of the Mediterranean Sea. Shallow and deep assemblages differed greatly both in species composition and abundance of morphological groups, leading to high between-habitat (beta) diversity related to a depth gradient. Moreover, patterns of spatial variability changed between habitats, resulting in greater large-scale variability in shallow habitat and greater small-scale variability in deep habitat. Finally, deep assemblages had a greater number of species than shallow assemblages. These findings have important implications for the management of Mediterranean coastal systems.

Assessing the Multidimensionality of Coastal Erosion Risks: Public Participation and Multicriteria Analysis in a Mediterranean Coastal System

The complex and multidimensional nature of coastal erosion risks makes it necessary to move away from single-perspective assessment and management methods that have conventionally predominated in coastal management. This article explores the suitability of participatory multicriteria analysis (MCA) for improving the integration of diverse expertises and values and enhancing the social-ecological robustness of the processes that lead to the definition of relevant policy options to deal with those risks. We test this approach in the Mediterranean coastal locality of Lido de Sète in France. Results show that the more adaptive alternatives such as "retreating the shoreline" were preferred by our selected stakeholders to those corresponding to "protecting the shoreline" and the business as usual proposals traditionally put forward by experts and policymakers on these matters. Participative MCA contributed to represent coastal multidimensionality, elicit and integrate different views and preferences, facilitated knowledge exchange, and allowed highlighting existing uncertainties.

The spread of Caulerpa racemosa var. cylindracea in the Mediterranean Sea: An example of how biological invasions can influence beta diversity

The present study aims to evaluate if invasion of Caulerpa racemosa var. cylindracea can affect both alpha and beta diversity in Mediterranean coastal system. The following hypotheses were tested: (i) measures of alpha diversity differ between invaded and non-invaded assemblages (ii) this pattern is consistent between different habitats, (iii) assemblages from habitats which are naturally very different tend to be more similar when invaded compared to non-invaded situations. Results showed that Mediterranean benthic assemblages invaded by C. racemosa var. cylindracea were characterized by lower values of alpha diversity than non-invaded assemblages; moreover, differences between deep (25 m) and shallow water (5m) assemblages appeared lower in invaded than in non-invaded areas, with a decrease of beta diversity. This homogenisation of habitats was related to a lack of several characteristic species and to a higher abundance of few opportunistic species in invaded areas, particularly turf-forming algae. Moreover, variability in taxa composition was lower in invaded than in non-invaded assemblages in both habitats.

Geratology and decomposition of Spartina versicolor in a brackish Mediterranean marsh

Most studies on plant decomposition in salt marshes have been carried out in Spartina-dominated marshes in North America. In contrast, few have focused on marshes in Mediterranean systems. Moreover, research into litter decay in estuarine systems has been conducted with plant material collected before natural senescence and death. Here we followed the growth, senescence, leaf fall, and nutrient dynamics of Spartina versicolor to examine litter decay in a Mediterranean coastal system. We studied the dynamics of fungi, meiofauna and algae associated with detached S. versicolor litter, and the effect of the microenvironment (above and underneath wracks of dead Spartina) on decomposition. The exponential decay coefficient rate ( k, day −1) was higher for leaves attached to standing plants (0.0019) than after leaf abscission (0.0002–0.001). The decomposition rate of detached leaves was highly variable and depended on the position of the litter. The large differences in decomposition rates between the two experimental conditions indicate that the microenvironment affected the associated litter community during the initial phase of decay. Water availability and high temperatures over the sediment surface increased the density of meiofauna and epiphyton and decreased fungal biomass during the first 20 days of the experiment. Fungal biomass was at the lower end of reported values, probably as a result of the drier conditions and high salinity in the Mediterranean marsh. Spartina versicolor detritus acted as a nutrient sink by immobilizing large amounts of N and P for at least one year.

Clonal growth dynamics of the invasive Carpobrotus affine acinaciformis in Mediterranean coastal systems: A non-linear model

Carpobrotus affine acinaciformis is one of the most harmful invasive plants in the Mediterranean basin. In this study, we built a numerical growth model containing simple, and essentially linear, growth rules that provided us a tool capable to analyse the complex non-linear behaviour observed in the dynamic growth of Carpobrotus spp. This model includes a set of ecologically relevant parameters such as: (1) the stolon elongation rate, setting the upper limit of the horizontal spreading of the clone, (2) the branching rate, closely related to the capacity of the plant to occupy the space forming a dense and complex network, (3) the branching angle, which is determinant in the efficiency of the space occupation during the growth process, (4) the node mortality, and (5) the node branching age. We found that young patches of Carpobrotus (<20 years old) are characterised by a biomass production and quantity and density of nodes that grow exponentially with an exponent that depends on the branching probability and the stolon elongation rate. The expansion in the diameter is initially produced from a very ramified morphology, characterised by a fractal dimension D f = 1.2 (100 nodes; <5 years old; velocidad ≈ 0.3 m/year) that later turns into a more compact plant with less occupied space in its interior (20,000 nodes; >50 years old; speed keeps oscillating around 0.27 m/year further on) with a dimension equal to the euclidean one ( D f = d = 2). Regarding the implications for the management of Carpobrotus, it is remarkable that with few relevant parameters we have been able to reproduce the patch dynamics of this plant, which may indeed be quite useful to improve the yield prediction of Carpobrotus growth in coastal Mediterranean zones. Our modelling approach can further be extended to interdisciplinary problems in which dendritic patterns and branched structures are developed.

Size-fractionated phytoplankton chlorophyll in an Eastern Mediterranean coastal system (Maliakos Gulf, Greece)

The dynamics of phytoplankton biomass were studied in an Eastern Mediterranean semi-enclosed coastal system (Maliakos Gulf, Aegean Sea), over 1 year. In particular, chlorophyll a (chl a) was fractionated into four size classes: picoplankton (0.2–2 µm), nanoplankton (2–20 µm), microplankton (20–180 µm) and net phytoplankton (>180 µm). The spatial and temporal variation in dissolved inorganic nutrients and particulate organic carbon (POC) were also investigated. The water column was well mixed throughout the year, resulting in no differences between depths for all the measured parameters. Total chl a was highest in the inner part of the gulf and peaked in winter (2.65 µg l–1). During the phytoplankton bloom, microplankton and net phytoplankton together dominated the autotrophic biomass (67.2–95.0% of total chl a), while in the warmer months the contribution of pico- and nanoplankton was the most significant (77.5–93.4% of total chl a). The small fractions, although showing low chl a concentrations, were important contributors to the POC pool, especially in the outer gulf. No statistically significant correlations were found between any chl a size fraction and inorganic nutrients. For most of the year, phytoplankton was not limited by inorganic nitrogen concentrations.

Observations of the Particle Size Distribution and Concentration in a Coastal System using an In Situ Laser Analyzer

An in situ laser particle size analyzer (LISST-100, Sequoia Scientific, Inc.) has been used to study the particle size distribution and concentration of biological and non biological particles in the water column of a Mediterranean coastal system. Two field campaigns have been carried out during low and high energy conditions of the flow, caused by the passage of a storm front. For the low energy period, the water column remained stratified, whereas for the high energetic period the water column was warmer and well mixed. The first study dealt with the distribution of particles near the bottom of the coastal area. Here, two regions were taken into account. The first region was a sea-grass meadow of Posidonia oceanica and the second region was a barren sand area. The second study dealt with the determination of the vertical distribution of suspended particles in the whole water column of the system. The results showed a decrease in the vertical concentration of suspended particles in the water column with the passage of the storm front, which was associated with advection of warm water mass rather than by vertical mixing. In contrast, vertical resuspension determined the fate of suspended particles at the bottom of the water column and an increase of their concentration was found.

Macrobenthos ofPotamogeton andMyriophyllum beds in the upper reaches of Canal de Mira (Ria de Aveiro, NW Portugal): Community structure and environmental factors

The community structure of the macrobenthic fauna (>0.5 mm) ofPotamogeton andMyriophyllum beds of the upper reaches of Canal de Mira (0.5<Sal<5) was studied monthly from May 1988 to April 1989 at three sampling stations. Environmental data included water, sediment and vegetation parameters measured monthly or seasonally. Four 24 hours sampling cycles were carried out in June, September and December 1988 and March 1989. The faunal data were subjected to ordination techniques (MDS) and a permutation test (two-way crossed layout) was used to assess spatial and temporal differences. The results showed significant differences between stations and a strong seasonal pattern in the community structure. The species responsible for sample groupings were determined by discriminant analysis using Bray-Curtis dissimilarities, and the faunal assemblages were studied in relation to the environmental factors. The results indicate that the main structuring factors of the community are plant biomass and water salinity at low tide. Station 2 exhibits both the highest values of plant biomass (DW=289 g m−2) and of macrofauna density (369, 240 ind m−2).Potamopyrgus jenkinsi, Corophium multisetosum andLimnodrilus hoffmeisteri are dominant species in the study area. The community of station 1 includes an important set of taxa usually associated to freshwater habitats (oligochaetes, leeches and insect larvae) whilst in station 3 typically estuarine species (Cyathura carinata, Leptocheirus pilosus, Nereis diversicolor, Streblospio shrubsolii) occur. A succession of peak densities of different taxonomic groups during the year indicates seasonal variation in the community structure. The faunal assemblage of the study area is compared with similar ones in NE Atlantic and Mediterranean coastal systems.