Maritime traffic and port activities pose several environmental and ecological problems in the marine environment. The purpose of this study was to provide baseline data for the future assessment of ...anthropogenic impacts related with port activities in Slovenian Sea (Northern Adriatic Sea). The macrobenthic communities near the port of Koper, as well as sites offshore were analysed. Results showed that the sites offshore were generally richer and more structured than sites inside the Port area. Those differences were explained partly by depth and sediment grain size. The ecological quality indicated by M-AMBI index resulted Good/High at all the sampling sites. However, the k-dominance curves indicated a disturbance at certain sites, in particular in the port channels. This work highlights the need for consistent monitoring programs to provide baseline data for future studies assessment of anthropogenic impacts.
•Macrobenthic communities in areas affected by maritime traffic.•Dominant biocoenosis of coastal terrigenous muds•Depth and sediment grain size influenced communities.•Ecological quality Good/High at all sites, but disturbance at certain sites.
Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century ...eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.
Organotin compounds (OTC), tri-, di- and monobutyl tin, were determined in the tissues of marbled electric ray (Torpedo marmorata) in the Adriatic Sea. Marbled electric ray specimens were provided by ...local fishermen from three localities in the northern Adriatic: area close to the shipyard in Seča, the natural protected area Strunjan Nature Reserve and along the west Istrian coast. To assess the concentration of OTC in the environment, sediment samples were also analysed. After an adequate extraction of OTC from both matrices, their concentrations were determined by GC-ICP-MS.
The results indicate that the accumulation of TBT (tributyltin) and DBT (dibutyltin) in the marbled electric ray is related to the possible pollution sources, since their total concentrations were significantly higher (p < 0.001) in the area close to the shipyard (up to 69 μg Sn kg−1, w.w.) in comparison to the other two areas less affected by direct pollution (up to 7 μg Sn kg−1, w.w.). TBT concentrations ranged from 2 to 42 μg Sn kg−1, w.w., DBT concentrations were in the range from 2 to 22 μg Sn kg−1, w.w., and MBT concentrations were mostly below the detection limit with the highest up to 4 μg Sn kg−1, w.w. The proportion of the three determined congener concentrations in sediment samples indicate a temporally older pollution with these compounds, with prevailing DBT and MBT concentrations up to 30 μg Sn kg−1, w.w., and much lower TBT concentrations up to 7 μg Sn kg−1, w.w.
According to our results, marbled electric ray could be considered as an ideal bioindicator of environmental pollution due to its ecological characteristics.
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•The first study on the OTC content of the marbled electric ray (Torpedo marmorata)•The accumulation of OTC is related to the possible sources of pollution.•Accumulation of OTC in the selected elasmobranch species is still significant.•Marbled electric ray could be an ideal bioindicator for environmental pollution.
A specimen of common thresher shark
(Bonnaterre 1788) was caught in a fishing net in the waters off Piran (Gulf of Trieste, northern Adriatic Sea). It was a juvenile male with a total length of 2841 ...mm. In recent decades, other cases of juvenile specimens of common thresher shark have been recorded in Slovenian coastal waters. Despite the drastic decline in the population of this species, thresher shark continues to be caught in local Adriatic fisheries.
Benthic indicators are important tools for the classification of coastal and transitional water bodies. The aim of the work was to assess for the first time the Environmental Status (ES) of Slovenian ...transitional waters, comparing the following biotic indices: richness, Shannon-Weaver diversity, AMBI, M-AMBI, BENTIX and BITS indices. A total of 13 stations were sampled with a Van Veen grab, in three ecosystems in the northern Adriatic. Samples were sieved and sorted, invertebrates identified and counted. The anthropogenic impact was estimated with professional judgement. Richness and diversity showed a good response to anthropogenic pressure. Conversely, indices based on sensitivity/tolerance groups did not showed a clear distinction between more and less impacted ecosystems. In particular BENTIX underestimated the ES, while with BITS there was a overestimation. The best evaluation was obtained with M-AMBI, because even if based on a sensitivity/tolerance approach, it considered also the structural aspect of the community.
•The status of Slovenian transitional waters was assessed for the first time.•Richness and diversity showed a good response to anthropogenic pressure.•Bentix underestimated the ecological quality.•The best evaluation was obtained with M-AMBI.
The authors studied the structure of the coastal fish assemblage in a temperate coral reef within a marine protected area in order to provide a baseline information on the occurrence and temporal ...distribution of fish and to highlight the importance of the coral reef to ichthyofauna. The coastal fish assemblage was investigated at two sites in Veliko jezero (Mljet National Park) in the southern Adriatic Sea with a non-destructive SCUBA visual technique in the period from 2013 to 2021. Altogether, 38 fish taxa were recorded on the right bank (coral reef) and 36 species on the left bank. The presence of the coral reef at a depth range between 9 m to 12 m is the main factor differentiating the fish fauna in these two areas, which are otherwise governed by the same environmental factors. At the coral reef a decrease in fish diversity was discovered with a steady regression from 2013 to 2021.
Sessile benthic communities are an important element of marine ecosystems, yet their temporal patterns remain poorly understood. For this reason, the temporal changes of the fouling community on ...brick plates in Piran Bay, Gulf of Trieste (northern Adriatic Sea), were studied for two calendar years. The aim of this study was to identify the settlement of dominant native and alien species on artificial substrates and their temporal occurrence, both in terms of season and duration of submersion. In addition, we tried to assess the impact of the placement period on developing communities. The dominant taxonomic groups were bryozoans, which accounted for almost half of the total coverage (46%), serpulid polychaetes (25%) and bivalves (11%). Most of the species belonging to the dominant taxa occurred throughout the year, with the peak of occurrence in summer. The first settlers included serpulids and bivalves, which were constantly found on the plates together with bryozoans. Alien and cryptogenic species represented about 13% of all taxa found during the study. This highlights the importance of bare artificial structures erected outside typical hotspots for alien species; they serve as a springboard for the spread of alien fouling species. The communities that formed on plates placed in different seasons showed significant differences between them. High bryozoan coverage characterized the communities placed in winter and spring, while the plates placed in summer and autumn were dominated by serpulid polychaetes. These differences are the result of species seasonality as well as the interaction between them. The study demonstrates the importance of timing for initial colonization. It can be linked to the placement of the bare substrate for the development of the community, and provides a baseline for research and projects involving underwater constructions and the detection of alien species.
Cystoseira s.l. forests are recognised as important habitats which host diverse coastal fish assemblages. Many fish species use such habitats as feeding, breeding, and nursery grounds. Since the ...coastal fish community depends on the availability of dense macroalgal belts, the decline of these habitats in the Mediterranean Sea also affects the density of coastal fish species. We studied the coastal fish assemblage in Cystoseira s.l. forests in three consecutive years 2019–2021 in the Gulf of Trieste (Adriatic Sea). Data on coastal fish fauna were collected by visual counts conducted by SCUBA diving. Data on algal cover and habitat types were obtained by recording with a video camera. Similarities and differences in the fish community were analysed in terms of habitat and substrate preferences. A total of 34 species were recorded in Cystoseira forests. The results of the present study show that the different algal cover and associated depth gradient have different effects on the fish assemblage in coastal waters, affecting species composition and abundance. For many species, particularly labrids and sea breams, there is a decreasing temporal trend in frequency of occurrence and density. However, fish community trends can be used as a good “proxy” to evaluate the algal belt status. Our results indicate that rapid conservation and restoration actions are needed to stem the decline of Cystoseira s.l. forests.
Marine phanerogams are considered biological sentinels or indicators since any modification in seagrass meadow distribution and coverage signals negative changes in the marine environment. In recent ...decades, seagrass meadows have undergone global losses at accelerating rates, and almost one-third of their coverage has disappeared globally. This study focused on the dynamics of seagrass meadows in the northern Adriatic Sea, which is one of the most anthropogenically affected areas in the Mediterranean Sea. Seagrass distribution data and remote sensing products were utilized to identify the stable and dynamic parts of the seagrass ecosystem. Different seagrass species could not be distinguished with the Sentinel-2 (BOA) satellite image. However, results revealed a generally stable seagrass meadow (283.5 Ha) but, on the other hand, a stochastic behavior in seagrass meadow retraction (90.8 Ha) linked to local environmental processes associated with anthropogenic activities or climate change. If systemized, this proposed approach to monitoring seagrass meadow dynamics could be developed as a spatial decision support system for the entire Mediterranean basin. Such a tool could serve as a key element for decision makers in marine protected areas and would potentially support more effective conservation and management actions in these highly productive and important environments.
The stony coral Cladocora caespitosa (Linnaeus, 1767) is an important Mediterranean habitat builder, whose survival is now being threatened by human activities and possibly natural events such as ...mass mortality and bleaching. We characterized the mollusc assemblage associated with colonies in the Gulf of Trieste (northern Adriatic Sea) and then tested whether the number of mollusc species increases in relation with colony size, following a Species-Area Relationship (SAR) model. At least 62 taxa were found in association with coral colonies, with bivalves constituting the dominant group. More than half of the 3034 specimens encountered were juveniles. Mollusc taxa richness increased with increasing C. caespitosa colony size according to the power-function model, whilst the analyses of trophic and functional groups supports the hypothesis of at least two factors underlying SAR (area per se and habitat diversity). Our results confirmed the importance of C. caespitosa for benthic communities, indicating that larger colonies support higher biodiversity, and suggesting that C. caespitosa is the most important habit builder among Mediterranean cnidarians, having also an influential function as a natural nursery ground. These results underline the necessity of new investigations aimed at filling gaps in our knowledge and planning new measures to protect the species.
•Molluscs associated with the coral Cladocora caespitosa were investigated.•Big colonies of C. caespitosa hosted higher number of molluscs taxa.•Area-per se and microhabitat diversity hypotheses explained colony size effect.•C. caespitosa is the most important habitat builder among Mediterranean cnidarians.•C. caespitosa constituted an important nursery ground for molluscs.
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