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.
Mercury (Hg) is one of the primary health concerns in natural and urbanised environments due to past and present natural and anthropogenic emissions. Its environmental cycle is driven by redox ...reactions, microbial metabolism and organic matter (OM) interactions, which may all lead to formation of bioaccumulative organic Hg species; methylmercury (MeHg), with damaging consequences for human and ecosystem health. Hence, Hg lability and bioavailability has been the focus of many investigations and assessed with a variety of chemical proxies in order to improve understanding of the conditions that lead to enhanced bioavailability of Hg and its species. We investigated Hg labile species with Diffusive Gradient in Thin-film technique (DGT) in the water column and sediment of Zenne River (Brussels, Belgium) and Gulf of Trieste (North Adriatic). They represent two contemporary important Hg-impacted areas; the former by anthropogenic urban pollution, and the latter by historic pollution from Hg mining. Hg speciation of labile inorganic and methylmercury in these two environments was not yet investigated using DGT technique. The results show labile Hg species changing with season in the water column of Zenne River, while the sediments are the source of bioavailable MeHg to the water column that is transported further creating a halo effect in the region. Values of labile Hg species for water column and sediments in Gulf of Trieste differ from previous research, highlighting the need for more investigation into Hg bioavailability. MeHg/THg ratios were compared to other sampling methods for labile Hg species.
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•Labile Hg species were measured using a Diffusive Gradient in Thin-film technique.•DGTs were used in the Zenne River Brussels and Gulf of Trieste (North Adriatic).•Winter-time THg in Zenne is highly labile and mobilized far from its source.•MeHg/THg% in Gulf showed higher labile Hg bioavailability than previously thought.•Labile MeHg in the sediment of the Gulf represents up to 75% of total labile Hg.
Mariculture along the Slovene coastline is mainly mussel culture operated as a family business; in one case, it is combined with sea bass farming. It started in the early 70 s with cultivation of ...Mediterranean mussels, while today, the two largest producers incorporate the cultivation of Venus clams and oysters as species with higher economic value on the market. Currently, all mussels and clams produced in Slovenia are sold in the Slovenian, Italian, Croatian and French markets. The production of Mediterranean mussels (Mytilus galloprovincialis) has increased steadily, with the main obstacles being a limited area for cultivation, occasional harmful algal blooms, predation by gilthead seabream and flatworms. In addition, more recent summer heatwaves negatively affected mussel production when seawater reached high temperatures at the thermal limits unsuitable for mussel growth. This study aimed to collect first-hand information about the current mussel production technology, processes and needs to identify opportunities for innovations that could benefit the entire sector (increased knowledge, production yield, reduced workload and effort with administrative issues). The study was based on a semi-structured questionnaire with the owners of mussel farms. Analysis of the questionnaire was supplemented with current knowledge from the field and provided comprehensive insight into a small sector of mussel farming along the Slovenian coast and its possible development in the future.
•Slovenian mussel production has short supply chains, mussels sell as a raw product, with no food processing industry.•The main threats to mussel production are predation by gilthead seabream and flatworms and summer heatwaves.•Mussel farmers noticed a lack of knowledge, a limited knowledge base, few dedicated learning opportunities in their business, and lack of innovations in production.•The allocation of mussel farms away from the coastline, farming the more valuable Venus clams and oysters and selling at the more demanding market may make the sector more resilient.
Mercury (Hg) in aquatic environments accumulates in sediments in several chemical forms, both inorganic and organic, which are often determined through time-consuming selective and sequential ...extraction procedures. Thermal desorption technique (pyrolysis) coupled with continuous determination by atomic absorption spectrometry (AAS) may be an easy-to-use alternative technique for the rapid identification and quantification of Hg species in the solid matrix. This technique is based on the gradual heating of a sample that releases Hg at different temperature intervals depending on its chemical form. Thus, a single Hg species that desorbs at a specific temperature may be identified via a thermogram of the sample.
In this work, several commercial pure Hg compounds, natural Hg mineral species (red cinnabar, α-HgS) and one compound synthesised in the lab (α-FeOOHHg) were mixed with synthetic calcium carbonate (CaCO3), silica (SiO2) and natural matrices (silicate and carbonate marine sediments) which were then desorbed in order to determine the desorption peak temperatures corresponding to each Hg species. Moreover, possible interference caused by the matrix was also considered. The results obtained from 52 desorbed MIX samples displayed different desorption temperatures for the same Hg species depending on the matrix used. Indeed, Hg species mixed with synthetic SiO2 desorbed at a temperature lower than the same species mixed with synthetic CaCO3 with a difference of approximately 100 °C.
The analytical approach was applied to selected coastal sediments from the Gulf of Trieste (Northern Adriatic Sea, Italy), contaminated by Hg from the five centuries of cinnabar (α-HgS) mining activity from Idrija (Slovenia), in order to identify the unknown Hg species. The results revealed the presence of two peaks with a distinct temperature of desorption (∼250 and 350 °C). The highest temperature corresponds to the mostly refractory red cinnabar (α-HgS) compound, whereas the lowest temperature is related to other species (e.g. β-HgS) that may also include Hg associated with more mobile and potentially bio-accessible species (e.g. α-FeOOHHg) if compared to α-HgS. This methodological approach is a rapid and cost-effective technique useful to preliminarily quantify more stable Hg species (mainly α-HgS), underlining the relevance in considering the chemical form of the element rather than merely the total concentration for simplifying the environmental management of Hg-contaminated sediments.
•Thermodesorption technique facilitates rapid identification of Hg species in solid matrix.•Commercial pure Hg compounds mixed with synthetic and natural matrices are desorbed.•Several desorption peak temperatures of each Hg species were obtained.•β-HgS (210–250 °C) and α-HgS (350–360 °C) was mainly identified in marine sediments.•Hg compounds with very low concentration are more difficult to be detected.
The present work aims to detect Lagrangian transport barriers in the Gulf of Trieste by means of Lyapunov-exponent approach and tensorlines of the Cauchy-Green tensor. Lagrangian Coherent Structures ...(LCSs) are calculated employing 2D surface velocity fields measured by the coastal radars of the TOSCA EU research project (Tracking Oil Spills & Coastal Awareness Network). Moreover, surface drifters were deployed during the project. Comparisons between Eulerian velocity of HF-radar fields and Lagrangian velocity of drifters are carried out alongside single-particle tracking reliability. In particular, the possible influence of the data gaps in the HF-radar fields have been carefully considered. LCSs have proven to be robust against the quality of the starting HF-radar fields, leading to helpful insights in drifter positions. Indeed, after 24-hour integration the observed position of the drifter is approximately 1.5 km far from the nearest LCS, while a standard approach based on single-particle computations leads to larger errors (up to 5–7 km). However, such result must be properly interpreted taking into account the elongated nature of LCSs. A comparison between two common diagnostic tools of Lagrangian barriers is performed: Finite-Time and Finite-Size Lyapunov Exponent fields are compared in order to assess whether the patterns detected by the two measures are comparable. Finally, a joint analysis between LCSs and single-particle tracking is carried out and the results suggest that it would be desirable to couple these two approaches in real applications.
•A comparison between Finite-Time and Finite-Size Lyapunov Exponents is carried out.•Lagrangian Coherent Structures are detected in a Mediterranean coastal area: the Gulf of Trieste.•Lagrangian Coherent Structures and observed/simulated drifter trajectories are compared.•A joint search approach between Lagrangian Coherent Structures and single particle tracking is proposed.
The Gulf of Trieste (GT), northeastern Adriatic, sits at the rigid edge of the Adria microplate representing the foreland of the adjoining Meso-Cenozoic External Dinarides and Southeastern Alps. The ...Adria-Eurasia plate boundary extends along the GT eastern coastline, depicted by the Karst Thrust, outer ramp of the SW-verging Dinarides. This separates the Cretaceous-Paleogene carbonates outcropping hundreds of meters on the Karst Plateau (hanging-wall) from their counterparts buried in the eastern gulf. Although the thrust has no evidence of historical and instrumental seismicity, a detailed seismic velocity field is needed to quantify reliable geometries in the foredeep, embedded in a tectonically active area where Adria is moving NNW-ward. Availability of a newly acquired marine multichannel seismic dataset, allowed us to provide the first well-constrained 3D P-wave velocity and depth model in the footwall of the Karst Thrust. Two iterative techniques, traveltime reflection tomography and depth seismic imaging, were applied on the data surveying the Dinaric foredeep. Our findings provide mean velocity values of 1700 m/s for the Quaternary sediments, 2900 m/s for the upper Eocene flysch turbidites, 4500 m/s for the lower flysch, 5000 m/s for the upper carbonates. The maximum flysch unit thickness results in about 1500 m and the top carbonates depth reaches about 1600 m below sea level, 1.7 km offshore Trieste, revealing the thrust is responsible for a minimum 1600–1800 m vertical throw. This study provides benefits for Adria geodynamic models and give new constraints for the geological and tectonic setting assessment, in a region settled over a currently active continental margin.
•Traveltime tomography and depth imaging from multichannel seismic in NE Adriatic.•3D velocity-depth model in marine Dinaric foredeep at NE Adria Plate (Gulf of Trieste).•Top of Meso-Cenozoic Carbonate Platform deepens NE-ward up to about 1.6 km bls.•Karst Thrust Dinaric outer ramp: minimum 1.8 km vertical throw at Trieste coast.
There is an increasing awareness of the relationships among key phytoplankton groups and their role in biogeochemical cycles; however, less is known about the temporal scales of variability in ...biodiversity of the phytoplankton community. In the present study a long-term data set (1986–2010) of phytoplankton abundance is used to investigate the temporal variability of the phytoplankton community at a coastal site in the Gulf of Trieste (northern Adriatic Sea). The interannual variability of the phytoplankton community shows two major periods in terms of abundance and community composition. The first one, 1986–1994, was characterized by the highest abundances of microalgae and the dominance of phytoflagellates. The second period (1995–2007) showed lower abundances and a collapse of phytoflagellates. Lastly, an apparent new increase in abundances has been recorded during recent years (2008–2010). On a seasonal scale, a classical cycle with two maxima (spring and autumn) and a summer minimum is evident. Diatoms are the most abundant group of the late winter–early spring bloom whereas phytoflagellates, the most abundant group throughout the year, dominate the late spring blooms. Dinoflagellates and coccolithophores have low abundances and show their maxima in summer and autumn, respectively. The species composition has been analysed according to the Indicator Value Index, highlighting the more frequent and abundant taxa for each month. Results show that the winter months are characterized by coccolithophores, in spring small diatoms are dominant, dinoflagellates and larger diatoms are typical in summer, and coccolithophores and diatom colonies characterise the autumn.
The Geoswim programme is an expedition-type project which is aiming to survey, monitor and measure the entire perimeter of rocky coasts of the Mediterranean Sea. The project officially started in ...2012 with the first one-man survey of 193.4 km by snorkeling along the northeastern Adriatic coasts, and is ongoing. So far, 559.5 km of rocky coasts have been surveyed, over 98 days of survey, and several hundred thousand time-lapse images, continuous videos and outline images have been collected, both above and below the waterline. Bathymetric data and physical/chemical parameters, such as temperature and electrical conductivity have also been collected during the snorkel surveys. Instruments are hosted on a specially-built raft, called instrumental-supported raft (ISR). The data are not homogeneous because over the years the approach has changed following the introduction of new technologies and some redesign of the instruments used, and, in part, also the type of data collected. Moreover, observational data for use in coastal studies and for integrating instrumental data are collected. The paper presents and take stock of the geometry of the database and discusses the main results of the Geoswim programme.
Data analysed highlighted that the database is a significant archive that provides 1) images and videos as a baseline for subsequent comparisons, 2) large amount of images to be used to build 3D models of coastal landforms, 3) data for statistics, and 4) a valuable source of possible discoveries of unknown coastal objects, such as sea caves, tidal notches at unexpected sites, ecological observations, etc.
•Presentation and take stock of the database of the Geoswim programme•Discussion of the potentialities of the swim-survey approach through published and new data collected during the expeditions•Analysis of the Geoswim programme and its evolution•Future perspectives of the programme
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