Τhis study aims to measure the abundance of microplastic (MP) particles in the soft tissue of mussel (Mytilus galloprovincialis) and pearl oyster (Pinctada imbricata radiata) specimens. Samples were collected at four sites in Greece (Sagiada, Malesina, Elounda, Rhodes) from wild and farmed populations. The identification of MPs was accomplished by Raman spectroscopy. Comparisons were made between the two different species where the two species co-existed (Malesina), between the four study sites (five sampling stations) in relation to P. imbricata radiata individuals, and also in every station for the different MP types found. For the specimens from Malesina, M. galloprovincialis had more MPs in their soft tissue compared to P. imbricata radiata. Microfibers were found in abundance in M. galloprovincialis, while microfragments were found in P. imbricata radiata specimens. The main MP type found in P. imbricata radiata specimens was microfragments in all five sampling stations, and ranged between 1.54 ± 0.63 (Rhodes-baskets) and 3.56 ± 0.35 (Sagiada) MP particles/g. While the samples of mussels and pearl oysters were similar in age, the differences found in the concentrations of MPs appears to be due to their different farming methods and location characteristics concerning the five sampling stations of pearl oysters. This study indicates that the culturing system does not affect MP concentration in bivalves, and further investigation is needed to find the most appropriate method to limit and reduce MPs that end up in the farmed organisms.

Nowadays, microplastic (MP) pollution has attracted increasing interest from the scientific community. This systematic review investigated the MP concentration in various tissues of five commercial fish species (Engraulis encrasicolus, Boops boops, Sardina pilchardus, Sardinella aurita, and Trachurus mediterraneus) in different Mediterranean water bodies in order to identify spatial trends and key analytes influencing their variation. The reported concentrations of MPs in all fish ranged from 4.2 particles/individual in the southeastern Mediterranean to 1.2 particles/individual in the western part, but these values are highly uncertain due to inconsistent methodologies, absence of recovery tests, and incomplete data reporting. No significant difference was found in the MP concentration of the different tissues of these species. The key factor affecting the MP concentration was the water body from which they were collected. This systematic review suggests that fewer than six samples may not provide statistically reliable results, and that a lack of detailed data reporting, despite the advances in chemical characterization techniques, continues to limit the robustness of MP studies. Additionally, this study evaluated how methodological differences could influence the reported MP concentrations. These findings offer a comprehensive overview of the MP expansion in the Mediterranean waterbodies and fish species, and provide recommendations for future research design improvement.

Fish farming in the Republic of Cyprus is carried out at offshore locations with mandatory, annual environmental impact monitoring conducted consistently in each fish farm, according to the national aquaculture legislative framework and following a state-mandated National Environmental Monitoring Protocol. This study aims to assess the findings of the implementation of the monitoring program over a 12-year period, by examining the variability of the benthic macrofaunal community and ecological quality status assessment through benthic indices across different factors. The results indicated that the classification by all indices was independent of the taxonomic variability from sample analysis, even if the community structure patterns varied significantly between the consultancies implementing the monitoring programs. The analysis from the combined benthic data showed that, unless specified by the presence of sensitive habitats, the effects were found to be at 50 m distance from the edge of the cages, since most indices revealed acceptable ecological quality at this distance. The BENTIX index, which is established under the Water Framework Directive and implemented within the context of the National Environmental Monitoring Protocol, highly correlated with all other indices. A cost-effective and taxonomic sufficient alternative is the BQI-Family index, since its thresholds are also calibrated for Eastern Mediterranean Sea.

Ports and recreational marinas are established hotspots for the introduction and secondary spread of non-indigenous species (NIS), mainly via vessel transport and biofouling on artificial substrates. In the AlienPorts project, we surveyed fouling and associated macrobenthic assemblages in four major Greek marinas across distinct marine regions—Rhodes (Levantine), Heraklion and Piraeus–Zea (Aegean), and Patra (Ionian)—from 2021 to 2022, applying two complementary protocols: (i) photoquadrat surveys and (ii) scraped assemblage sampling. The photoquadrats recorded twelve NIS and seven cryptogenic species, which were dominated by sessile fouling taxa, especially ascidians. The scraped samples revealed 106 polychaete and amphipod species, including 25 taxa (23 NIS, two cryptogenic). Six of the polychaetes are new NIS for the Mediterranean, and thirteen of the taxa are newly recorded as NIS in Greek waters. Heraklion had the highest NIS richness (18 NIS + two cryptogenic), while the other marinas hosted approximately ten NIS/cryptogenic taxa. In contrast, NIS often dominated the population densities, with Zea being the most impacted based on the NIS to native species ratios for both diversity and abundance. The two methods detected largely distinct biodiversity components and shared only one NIS, underscoring a strong complementarity. The multivariate analyses confirmed significant differences among marinas (ANOSIM, p < 0.01). These results support integrated, multi-method monitoring to enhance the early detection and impact assessment under MSFD Descriptor 2.

The increasing commercial value of holothurians has triggered considerable scientific interest. The aim of the study was to investigate Holothuria (Roweothuria) poli populations and sediment characteristics in two contrasting coastal areas in the same geographic region. The first (S1) consists of an exposed sandy, low organic material and well-oxygenated seabed. The other (S2) is sheltered, with a silty sediment, high labile organic matter, and negative redox values. H. poli populations were studied monthly by means of ROV survey while sediment samples were collected seasonally. At S2, holothurians were significantly more abundant and with higher biomass. In both areas, seasonal patterns were observed, with S1 presenting a peak of density and biomass during the summer months, while in S2 the peak was recorded in spring. The H. poli distribution seemed to be determined by environmental and biological factors, including availability of food resources, redox regime in the sediments and spawning-related behaviour.