Phthalate levels in common sea anemone Actinia equina and Anemonia viridis: A proxy of short-term microplastic interaction?

Phthalates are widely employed plasticizers blended to plastic polymers that, during plastic aging and weathering are prone to leach in the surrounding environment. Thus, phthalates were proposed to indirectly evaluate MPs contamination in marine environments, with still uncertain and scarce data, particularly for wildlife. This study investigates simultaneously microplastics (MPs) and phthalates (PAEs) occurrence in wild Actinia equina and Anemonia viridis, two common and edible sea anemone species. Both species had a 100 % frequency of MPs occurrence, with similar average concentrations. PAEs were detected in 70 % of samples, with concentrations up to 150 ng/g in A. equina and 144.3 ng/g for A. viridis. MPs and PAEs present in sea anemone tissues appear to reflect seawater plastic contamination conditions in the study area. Given the rapid biodegradation of PAEs, occurrence and concentrations of both these additives and their metabolites could be useful tracers of short-term plastic debris-biota interactions.

Microplastics evidence in yolk and liver of loggerhead sea turtles (Caretta caretta), a pilot study.

The potential toxicity of microplastics is a growing concern for the scientific community. The loggerhead sea turtle (Caretta caretta) is particularly inclined to accidently ingest plastic and microplastic due to its long-life cycle features. The possible transfer of microplastics from the female to the eggs should be investigated. The present study investigated the presence of microplastics in yolk and liver samples evaluating the number of melanomacrophages in the hepatic tissue as a possible biomarker of microplastics impact on the embryonic health status. The biometric parameters and liver histological analysis of 27 and 48 embryos (from two different nests respectively) at the 30 stage of development were analyzed. Raman Microspectroscopy was performed to identify the microplastics after alkaline digestion (10% KOH) of yolk and portion of liver from 5 embryos at the 30 developmental stage per nest. Microplastics were found in yolk and liver of loggerhead sea turtles at late embryonic stage for the first time. All microplastics were smaller than 5 µm and were made of polymers and colors suggesting their diverse origins. A total number of 21 microplastics, with dimensions lower than 5 µm, were found between the two nests (11 and 10 microplastics respectively). Only two shape categories were identified: spheres and fragments. The most frequent polymers observed were polyethylene, polyvinyl chloride and acrylonitrile butadiene styrene (31.5%, 21.1% and 15.8% respectively). Despite the eggs showing a higher number of microplastics in yolk samples than liver (15 and 6 microplastics in yolk and liver respectively), a positive correlation was observed only between the number of melanomacrophages (r = 0.863 p < 0.001) and microplastics in the liver. This result may suggest that microplastics could exert some effects on the hepatic tissues. Future studies should investigate this aspect and the possible relation between microplastics and other stress biomarkers.

Tracing the route: Using stable isotope analysis to understand microplastic pathways through the pelagic-neritic food web of the Tyrrhenian Sea (Western Mediterranean).

This study provides a pilot investigation of the relationship between microplastic ingestion and the trophic ecology of three pelagic fish species (Engraulis encrasicolus, Scomber scombrus, and Trachurus trachurus) from Anzio coast, Tyrrhenian Sea (Western Mediterranean). Stable isotope analysis has been performed to determine the trophic position and the isotopic niche of the three species. Then, data on the occurrence, abundance, and diversity of ingested microplastics have been analyzed considering the observed foraging patterns. The detected differences in the estimated trophic position (E. encrasicolus = 3.08 ± 0.18; S. scombrus = 3.57 ± 0.21; T. trachurus = 4.07 ± 0.21), together with the absence of overlap in the isotopic niches confirm that the three examined species cover different ecological roles within the coastal-pelagic food web. Results from the analysis of ingested microplastics show that the trophic position has no remarkable effects on the incidence of microplastic ingestion, with no significant differences detected in terms of both frequency of occurrence and number of ingested microplastics per individual. However, differences among species emerge when considering the diversity of ingested microplastic types in terms of shape, size, color, and polymer composition. Species at higher trophic levels have shown to ingest a greater diversity of microplastics, including a significant increase in the size of the ingested particles (median surface area: 0.011 mm2 in E. encrasicolus; 0.021 mm2 in S. scombrus; 0.036 mm2 in T. trachurus). The ingestion of larger microplastics might be due to the larger gape sizes but also to active selection mechanisms, likely stimulated by the similarity of these particles to natural or potential prey of both S. scombrus and T. trachurus. Overall, this study suggests that microplastic ingestion can be affected by the different trophic position of fish species, providing new insights about the impact of microplastic contamination on the pelagic community.

Dietary Preferences of Loggerhead Sea Turtles (Caretta caretta) in Two Mediterranean Feeding Grounds: Does Prey Selection Change with Habitat Use throughout Their Life Cycle?

According to their life stage, the loggerhead sea turtle (Caretta caretta) is found in a wide range of habitats, from neritic to more oceanic areas. Their feeding habits are expected to change as they develop, along with habitat use. Juvenile sea turtles are hypothesized to feed on pelagic species in oceanic areas, shifting to more benthic prey during the subadult and adult stages. We analyzed the gastrointestinal content from 150 loggerhead sea turtles stranded and/or bycaught along the Adriatic coast of the Abruzzo and Molise regions (n = 89) and the Tyrrhenian coast of the Lazio and Campania regions (n = 61) from 2018 to 2021. Food items were identified to the lowest taxonomic level, and the frequency of occurrence was calculated for each taxon and most recurrent species to assess changes in prey selection during the development. The marine litter was categorized, and the frequency of occurrence was calculated for the ingestion of litter. The most recurrent taxonomic prey group recorded in the Adriatic sample was Arthropoda (94%), followed by Mollusca (63%) and Chordata (34%). In the Tyrrhenian sample, loggerhead sea turtles fed mostly on Mollusca (84%), Arthropoda (38%), and Chordata (26%). Surprisingly, the Adriatic-Tyrrhenian sample groups showed similar feeding behavior between juveniles, subadults, and adults. A similar correlation has been observed concerning the ingestion of litter. Moreover, this study confirms the opportunistic feeding behavior of loggerhead sea turtles and their high adaptability.

From inshore to offshore: distribution of microplastics in three Italian seawaters.

A comprehensive understanding of the concentration of microplastics (MPs) in seawaters is essential to implement monitoring programs and understand the impacts on ecosystems, as required by the European legislation to protect the marine environment. In this context, the purpose of this study is to investigate the composition, quantity, and spatial distribution of microplastics from coastal to offshore areas in three Italian seawaters. In addition, the distribution of microplastics between surface and subsurface water layers was analyzed in order to better understand the dynamics of MPs in the upper layers of the water column. A total number of 6069 MPs (mean total concentration of 0.029 microplastics · m-2) were found to be heterogeneous in type, shape, and color. In general, MPs concentrations decrease with coastal distance, except when environmental forcings are predominant (such as sea currents). Moreover, the amount of surface MPs was almost four times that of subsurface microplastics, which consisted mostly of fibers. In light of these results, it becomes clear how critical it is to plan remediation actions and programs to minimize microplastic accumulations in the sea.

Image processing tools in the study of environmental contamination by microplastics: reliability and perspectives.

Microplastic pollution is one of the greatest environmental concerns for contemporary times and the future. In the last years, the number of publications about microplastic contamination has increased rapidly and the list is daily updated. However, the lack of standard analytical approaches might generate data inconsistencies, reducing the comparability among different studies. The present study investigates the potential of two image processing tools (namely the shapeR package for R and ImageJ 1.52v) in providing an accurate characterization of the shape of microplastics using a restricted set of shape descriptors. To ascertain that the selected tools can measure small shape differences, we perform an experiment to verify the detection of pre-post variations in the shape of different microplastic types (i.e., nylon [NY], polyethylene [PE], polyethylene terephthalate [PET], polypropylene [PP], polystyrene [PS], and polyvinylchloride [PVC]) treated with mildly corrosive chemicals (i.e., 10% KOH at 60 °C, 30% H2O2 at 50 °C, and 15% H2O2 + 5% HNO3 at 40 °C; incubation time ≈ 12 h). Analysis of surface area variations returns results about the vulnerability of plastic polymers to digestive solutions that are aligned with most of the acquired knowledge. The largest decrease in surface area occurs for KOH-treated PET particles, while NY results in the most susceptible polymer to the 30% H2O2 treatment, followed by PVC and PS. PE and PP are the most resistant polymers to all the used treatments. The adopted methods to characterize microplastics seem reliable tools for detecting small differences in the shape and size of these particles. Then, the analytic perspectives that can be developed using such widely accessible and low-cost equipment are discussed.

Drivers of litter ingestion by sea turtles: Three decades of empirical data collected in Atlantic Europe and the Mediterranean.

Sea turtles are considered as bio-indicators for monitoring the efficiency of restoration measures to reduce marine litter impacts on health. However, the lack of extended and standardised empirical data has prevented the accurate analysis of the factors influencing litter ingestion and the relationships with individual health. Historic data collected from 1988 and standard data collected from 2016 were harmonised to enable such analyses on necropsied loggerhead turtles (Caretta caretta) in eight Mediterranean and North-East Atlantic countries. Litter was found in 69.24 % of the 1121 individuals, mostly single-use and fishing-related plastics. Spatial location, sex and life history stage explained a minor part of litter ingestion. While no relationships with health could be detected, indicating that all individuals can be integrated as bio-indicators, the mechanistic models published in literature suggest that the high proportion of plastics in the digestive contents (38.77 % per individual) could have long-term repercussions on population dynamics.

One is not enough: Monitoring microplastic ingestion by fish needs a multispecies approach.

The development of monitoring programs based on bioindicators is crucial for assessing the impact of microplastic ingestion on marine organisms. This study presents results from an Italian pilot action aimed at investigating the suitability of a monitoring strategy based on a multispecies approach. The benthic-feeder Mullus barbatus, the demersal species Merluccius merluccius, and the pelagic-feeder species of the genus Scomber were used to assess the environmental contamination by microplastics in three different marine areas, namely Ancona (Adriatic Sea), Anzio (Tyrrhenian Sea), and Oristano (Western Sardinia). Microplastic ingestion frequencies were higher in samples from Anzio (26.7 %) and Ancona (25.0 %) than Oristano (14.4 %), suggesting a relationship between microplastic bioavailability and the proximity to urban settlements and river flows. Furthermore, microplastic ingestion was affected by the feeding habits of the examined species. The detected differences reinforce the hypothesis that a multispecies approach is needed to evaluate microplastic ingestion by marine animals.

Polymer composition assessment suggests prevalence of single-use plastics among items ingested by loggerhead sea turtles in the western mediterranean sub-region.

The ingestion of plastic is becoming a major concern for various species and particularly for marine turtles across the globe. The loggerhead sea turtle (Caretta caretta) was recently chosen by the European Commission as a bio-indicator for plastic pollution within the Mediterranean basin. We further investigated which items this key species is more prone to ingest, following the standardised Marine Strategy Framework Directive protocols. Moreover, we integrated to this protocol the Fourier Transform Infrared Spectroscopy, which allowed us to determine the polymer type of each item. We analysed samples from 226 sea turtles from 2008 to 2017 in two areas of the western Mediterranean sub-region (sensu MSFD). In the Lazio area we found a frequency of occurrence of plastic ingestion of 78.33%, while in Sardinia 41.79%. The analysis of the litter categories, among all individuals, highlights a prevalence of user-sheet (Use-She; 69.13%) and user-fragment plastics (Use-Fra; 20.84%). In addition, the polymer analysis showed a dominance of polyethylene (65.98%) and polypropylene (26.23%). As a result, by looking at other works that have investigated polymer types and items sources, we are able to infer that 77.25% of the objects ingested by the C. caretta individuals are attributable to disposable daily-life objects managed in an improper way. Therefore, C. caretta apart from being an efficient bio-indicator for plastic pollution, highlighting spatial and temporal concentration differences, it could also be used to verify the effectiveness of the Single-use Plastic Directive (EU 2019/904).

Using Boops boops (osteichthyes) to assess microplastic ingestion in the Mediterranean Sea.

This study assesses microplastic ingestion in Boops boops at different geographical areas in the Mediterranean Sea. A total of 884 fish were caught at 20 coastal sites in Spain, France, Italy and Greece and analyzed using a common methodological protocol. Microplastics were found in 46.8% of the sampled fish, with an average number of items per individual of 1.17 ± 0.07. Filaments were the predominant shape type, while polyethylene and polypropylene were indicated by FTIR as the most common polymer types of ingested microplastics. The frequency of occurrence, as well as the abundance and proportion of types (size, shape, color and polymer) of ingested microplastics, varied among geographical areas. The spatial heterogeneity of the abundance of ingested microplastics was mainly related to the degree of coastal anthropogenic pressure at the sampling sites. Our findings further support the suitability of B. boops as bioindicator of microplastic pollution in the Mediterranean Sea.

Macro-litter ingestion in deep-water habitats: is an underestimation occurring?

Marine litter affects marine organisms, posing threats to biodiversity conservation and to ecosystem structure and functioning. Providing a suitable assessment of marine litter effects on marine life through bioindicator species is crucial to drive an effective waste management policy. However, to date no standardized tool has been developed to describe and monitor the impact of marine macro-litter on marine life within deep-water habitats. Modifying the protocol proposed to monitor macro-litter ingestion by the loggerhead sea turtle Caretta caretta, we perform a preliminary investigation on the suitability of different elasmobranch species for monitoring macro-litter ingestion in deep-sea. A total of 122 specimens representing 7 elasmobranch species were collected and examined. External visual inspections documented no clear evidences of disease due to marine litter entanglement. A total of 7 ingested litter items were found in the stomach or in the esophagus of 6 specimens of 4 different species (frequency of occurrence = 4.9%), with a maximum number of 2 items per specimen. No litter items were found in the intestinal contents, as well as no evidence of gastrointestinal blockages due to litter items were detected. The low number of collected litter items suggests that the number of samples required is too large for a feasible monitoring program. Moreover, we observed that the anatomy of the intestinal spiral valve may represent an obstacle to the transit of macro-litter items, which could be spontaneously regurgitated as it happens in the selective elimination of undigested remains, such as bones and scales. Therefore, macro-litter retention time in the gastrointestinal tract of elasmobranchs could be brief and shorter than retention time of food. This may lead to an underestimation of macro-litter ingestion frequency by deep-water elasmobranchs. This study reports the first evidence of plastic ingestion by the kitefin shark Dalatias licha.

Spatial variability and influence of biological parameters on microplastic ingestion by Boops boops (L.) along the Italian coasts (Western Mediterranean Sea).

Recently, many studies focus on the ingestion of microplastics by marine biota. Fish exploit almost every kind of marine environment, occupy many ecological niches and are an important food source for human populations worldwide. For these reasons, they seem to represent very appropriate biological indicators of microplastic ingestion. UNEP/MAP SPA/RAC (2018) identified the bogue, Boops boops (Linnaeus, 1758), as a possible target species for monitoring microplastic ingestion in fish populations. This study provides the first report of microplastic ingestion by B. boops from the Tyrrhenian and the Ligurian Seas (Western Mediterranean Sea). Generalized Linear Mixed Models were used to analyse the relationship among biological parameters and environmental factors. A total of 379 bogues were collected in three Italian regions, subject to different anthropogenic pressures (river input, human population, shipping lanes and distance from the coast). Microplastics were detected in the gastrointestinal tract of most individuals (56%) with a mean of 1.8 (±0.2) microplastics per individual. Our study further confirms that this species is able to highlight differences in the ingestion of microplastics according to local anthropization, resulting Latium region to be the most polluted. Fish with lower physical condition are more likely to ingest microplastics, suggesting a relationship with the level of local environmental contamination. Finally, the ingestion of microplastics might be influenced by behavioural differences between sexes. According to our results, males ingest significantly more microplastics than females (p < 0.05). Our research confirms that an extensive knowledge on the biology of a bioindicator species is a priority for developing a valid monitoring strategy, such as the Marine Strategy Framework Directive for European waters.

Food preference determines the best suitable digestion protocol for analysing microplastic ingestion by fish.

Microplastic presence in the marine environment has generated considerable concern. Many procedures for microplastics detection in fish gastrointestinal tract have been recently developed. In this study, we compared efficiencies of two common procedures applied for the digestion of organic matter (10% KOH; 15% H2O2) with a new proposal (mixture of 5% HNO3 and 15% H2O2). We considered ecological diversity among species and differences in their diet compositions as factors that could affect the efficiency and feasibility of analytical approaches. Our aim was to understand whether either one of the three protocols might be suitable for all species or it might be more advisable to select a method according to the gut content determined by different food preferences. The results showed that the trophic level and feeding habits should be considered for protocol selection. Finally, we applied the best protocols on samples from the Tyrrhenian sea.

Exploring microplastic ingestion by three deep-water elasmobranch species: A case study from the Tyrrhenian Sea.

This study analyzes microplastic ingestion by three deep-water elasmobranch species (Galeus melastomus, Scyliorhinus canicula and Etmopterus spinax) from the Tyrrhenian Sea, discriminating between stomach and intestine contents. The absence of significant differences in frequency and abundance of plastic items into stomachs seems to suggest that ecological diversity among the three sharks does not strongly influence the probability of plastic ingestion in the study area. On the other hand, the detected differences in the microplastic content into the intestine might be due to a different retention time of microplastics, suggesting how feeding habits could influence metabolic features, and therefore affect the recovery of ingested plastic items. This information would improve the future development of marine micro-litter monitoring systems, following the MSFD requirements. Moreover, this study shows that all the three examined elasmobranch species can give important information even with relatively small sample sizes (N ≈ 30), and they could be used as target species for monitoring micro-litter ingestion in deep-water habitats.

Data Collection on Marine Litter Ingestion in Sea Turtles and Thresholds for Good Environmental Status.

The following protocol is intended to respond to the requirements set by the European Union's Marine Strategy Framework Directives (MSFD) for the D10C3 Criteria reported in the Commission Decision (EU), related to the amount of litter ingested by marine animals. Standardized methodologies for extracting litter items ingested from dead sea turtles along with guidelines on data analysis are provided. The protocol starts with the collection of dead sea turtles and classification of samples according to the decomposition status. Turtle necropsy must be performed in authorized centers and the protocol described here explains the best procedure for gastrointestinal (GI) tract isolation. The three parts of the GI (esophagus, stomach, intestine) should be separated, opened lengthways and contents filtered using a 1 mm mesh sieve. The article describes the classification and quantification of ingested litter, classifying GI contents into seven different categories of marine litter and two categories of natural remains. The quantity of ingested litter should be reported as total dry mass (weight in grams, with two decimal places) and abundance (number of items). The protocol proposes two possible scenarios to achieve the Good Environmental Status (GES). First: "There should be less than X% of sea turtles having Y g or more plastic in the GI in samples of 50-100 dead turtles from each sub-region", where Y is the average weight of plastic ingested and X% is the percentage of sea turtles with more weight (in grams) of plastic than Y. The second one, which considers the food remain versus plastic as a proxy of individual health, is: "There should be less than X% of sea turtles having more weight of plastic (in grams) than food remains in the GI in samples of 50-100 dead turtles from each sub-region".

Determining suitable fish to monitor plastic ingestion trends in the Mediterranean Sea.

The presence of marine litter is a complex, yet persistent, threat to the health and biodiversity of the marine environment, and plastic is the most abundant, and ubiquitous type of marine litter. To monitor the level of plastic waste in an area, and the prospect of it entering the food chain, bioindicator species are used extensively throughout Northern European Seas, however due to their distribution ranges many are not applicable to the Mediterranean Sea. Guidance published for the Marine Strategy Framework Directive suggests that the contents of fish stomachs may be analyzed to determine trends of marine plastic ingestion. In order to equate transnational trends in marine plastic ingestion, the use of standardized fish species that widely occur throughout the basin is favoured, however for the Mediterranean Sea, specific species are not listed. Here we propose a methodology to assess how effective Mediterranean fish species, that are known to have ingested marine plastic, are as bioindicators. A new Bioindicator Index (BI) was established by incorporating several parameters considered important for bioindicators. These parameters included species distribution throughout the Mediterranean basin, several life history traits, the commercial value of each species, and the occurrence of marine litter in their gut contents. By collecting existing data for Mediterranean fish, ranked scores were assigned to each trait and an average value (BI value) was calculated for each species. Based on their habitat preferences, Engraulis encrasicolus (pelagic), Boops boops (benthopelagic), three species of Myctophidae (Hygophum benoiti, Myctophum punctatum and Electrona risso) (mesopelagic), Mullus barbatus barbartus (demersal) and Chelidonichthys lucerna (benthic), were identified as currently, the most suitable fish for monitoring the ingestion of marine plastics throughout the Mediterranean basin. The use of standardized indicator species will ensure coherence in the reporting of marine litter ingestion trends throughout the Mediterranean Sea.

Loggerhead sea turtles (Caretta caretta): A target species for monitoring litter ingested by marine organisms in the Mediterranean Sea.

Marine litter is any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. Ingestion of marine litter can have lethal and sub-lethal effects on wildlife that accidentally ingests it, and sea turtles are particularly susceptible to this threat. The European Commission drafted the 2008/56/EC Marine Strategy Framework Directive with the aim to achieve a Good Environmental Status (GES), and the loggerhead sea turtle (Caretta caretta, Linnaeus 1758) was selected for monitoring the amount and composition of litter ingested by marine animals. An analogous decision has been made under the UNEP/MAP Barcelona Convention for the protection of the Mediterranean Sea, following the Ecosystem Approach. This work provides for the first time, two possible scenarios for the Marine Strategy Framework Directive GES, both related to "Trends in the amount and composition of litter ingested by marine animals" in the Mediterranean Sea. The study validates the use of the loggerhead turtle as target indicator for monitoring the impact of litter on marine biota and calls for immediate use of this protocol throughout the Mediterranean basin and European Region. Both GES scenarios are relevant worldwide, where sea turtles and marine litter are present, for measuring the impact of ingested plastics and developing policy strategies to reduce it. In the period between 2011 and 2014, 150 loggerhead sea turtles, found dead, were collected from the Italian Coast, West Mediterranean Sea Sub-Region. The presence of marine litter was investigated using a standardized protocol for necropsies and lab analysis. The collected items were subdivided into 4 main categories, namely, IND-Industrial plastic, USE-User plastic, RUB-Non plastic rubbish, POL-Pollutants and 14 sub-categories, to detect local diversity. Eighty-five percent of the individuals considered (n = 120) were found to have ingested an average of 1.3 ± 0.2 g of litter (dry mass) or 16 ± 3 items.

Amount and distribution of neustonic micro-plastic off the western Sardinian coast (Central-Western Mediterranean Sea).

A plethora of different sampling methodologies has been used to document the presence of micro-plastic fragments in sea water. European Marine Strategy suggests to improve standard techniques to make future data comparable. We use Manta Trawl sampling technique to quantify abundance and distribution of micro-plastic fragments in Sardinian Sea (Western Mediterranean), and their relation with phthalates and organoclorine in the neustonic habitat. Our results highlight a quite high average plastic abundance value (0.15 items/m(3)), comparable to the levels detected in other areas of the Mediterranean. "Site" is the only factor that significantly explains the differences observed in micro-plastic densities. Contaminant levels show high spatial and temporal variation. In every station, HCB is the contaminant with the lowest concentration while PCBs shows the highest levels. This work, in line with Marine Strategy directives, represents a preliminary study for the analysis of plastic impact on marine environment of Sardinia.

Interaction between loggerhead sea turtles (Caretta caretta) and marine litter in Sardinia (Western Mediterranean Sea).

Anthropogenic debris in the environment affects many species that accidentally ingest it. The aim of this study is to evaluate the quantity and composition of marine litter ingested by loggerheads in Sardinia, thus supplying for the lack of data in the existing literature for this area. Seventeen of the 121 (14.04%) monitored turtles presented debris in their digestive tracts. Litter in faecal pellet of alive individuals (n = 91) and in gastro-intestinal contents of dead ones (n = 30) was categorized, counted and weighed. User plastic was the main category of ingested debris with a frequency of occurrence of 13.22% of the total sample, while sheet (12.39%) and fragments (9.09%) were the most relevant sub-categories. This study highlights for the first time the incidence of litter in alive turtles in Sardinia. This contribution improves the knowledge about marine litter interaction on Caretta caretta as bio-indicator. Results will be useful for the Marine Strategy implementation.

Sewage pollution impact on Mediterranean rocky-reef fish assemblages.

The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical after control/impact (ACI) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.