Central Adriatic Sea Research Articles

Application of Positive Matrix Factorization for Source Apportionment of Polycyclic Aromatic Hydrocarbons (PAH) in the Adriatic Sea, and the Evaluation of PAH-Related Carcinogenic Risks

Concentrations of polycyclic aromatic hydrocarbons (PAH) were studied in 36 sediment samples collected from 29 sites in the central Adriatic Sea. The total concentration of PAH showed high variability, ranging from 42.85 µg kg−1 in open sea sediments to 28,662 µg kg−1 in the sediments of Šibenik Bay. Unsubstituted, parent PAH were dominant PAH compounds in the entire area of Šibenik Bay and most of the stations in the coastal area. In Kaštela Bay, methyl PAH concentrations were higher than the concentrations of unsubstituted PAH, whereas in the sediments along the mid-Adriatic transect, similar concentrations of both PAH fractions were determined. PAH sources were investigated by applying the Positive Matrix Factorization software developed by the U.S. Environmental Protection Agency (USEPA). The results indicate the presence of four sources, two of which can be considered petrogenic and two pyrogenic. The contribution of the sources to the total concentration PAH at each station indicates the dominance of pyrogenic sources in Šibenik Bay and at most stations in the coastal area. In the sediments along the mid-Adriatic transversal, as well as in Kaštela Bay, PAHs originate mainly from petrogenic sources. The obtained results show that PMF can be a suitable tool for control of PAH pollution and thus, for the management of various activities in the Adriatic region. Seasonal differences between the contributions of sources in the Kaštela and Šibenik bays indicate that the contribution of traffic to the total concentration of PAH was higher during the tourist season. The carcinogenic risk of PAH determined by toxicity equivalent (TEQ) calculations showed an increased carcinogenic risk in the whole area of Šibenik Bay, regardless of the number of PAH compounds considered for the calculations. A low PAH-related carcinogenic risk was found for the rest of the study area.

Recruitment of Oysters by Different Collection Devices at a Longline Shellfish Farm in the Central Adriatic Sea

In 2020–2021, a trial to recruit flat oysters was implemented at a longline farm in the central Adriatic, whereby the efficiency recruitment (n. oyster/dm2) of different suspended substrates was evaluated. Two lantern nets (50 cm diameter; 145 cm h) had different substrates composed of 8 mm wide wrinkled ribbon and empty oyster shells positioned in the upper levels of the lanterns. The tumbling evaluation and the presence of mud were also considered. The efficiency recruitment was similar between the wrinkled ribbon and the oyster shell. Recruitment was in the same proportion on the external rough part of the shells as on the internal smooth part of the shells. No significant differences were shown when comparing the different substrates in terms of recruitment efficiency.

Picoplankton diversity in an oligotrophic and high salinity environment in the central Adriatic Sea

By combining qualitative 16S metabarcoding and quantitative CARD-FISH methods with neural gas analysis, different patterns of the picoplankton community were revealed at finer taxonomic levels in response to changing environmental conditions in the Adriatic Sea. We present the results of a one-year study carried out in an oligotrophic environment where increased salinity was recently observed. We have shown that the initial state of community structure changes according to environmental conditions and is expressed as qualitative and quantitative changes. A general pattern of increasing diversity under harsh environmental conditions, particularly under the influence of increasing salinity at the expense of community abundance was observed. Considering the trend of changing seawater characteristics due to climate change, this study helps in understanding a possible structural change in the microbial community of the Adriatic Sea that could affect higher levels of the marine food web.

Extinct but not entirely: A new occurrence of the critically endangered Squatina squatina (Linnaeus, 1758) stresses the urgency of its conservation in the Adriatic sea

The common angel shark (Squatina squatina), a critically endangered species inhabiting the Mediterranean Sea, has been extirpated and considered locally extinct in the Adriatic Sea due to historical intense targeted fisheries. Sighting and catches of the species are indeed currently occasional in the area. Here, we present a new record of a juvenile of common angel shark in the central Adriatic Sea and we review 135 additional specimens documented in the area since 2000s, after 40-years of no sightings. According to previous findings, our evidence suggest that the central Adriatic Sea may be a relevant habitat for early life stages of common angel shark. Due to the serious threatened status of the species, we stress the importance of urgent conservation actions needed in the Adriatic Sea.

Biphasic versus monophasic growth curve equation, an application to common sole (Solea solea, L.) in the northern and central Adriatic Sea

Traditionally, growth patterns are described as constant throughout life using von Bertalanffy's equation. However, a change in growth due to a reallocation of energy during an individual’s lifespan is to be expected. Following this hypothesis, back-calculation measurements obtained from SoleMon survey data were used to fit and compare monophasic and biphasic growth curves for common sole in the northern and central Adriatic Sea. Moreover, individual variability in growth was considered through nonlinear mixed-effect models in which the individual parameters were considered as a random effect. The analyses performed in this study revealed systematic age-specific discrepancies in the monophasic curve and demonstrated that the fit of the biphasic curve was superior (Δ AIC: 329; Δ BIC: 310), confirming the theory that growth in size would decrease as a consequence of reproductive effort. Finally, since common sole is routinely assessed using models that rely on growth to derive assessment estimates and related management reference points, a stock assessment simulation was performed to compare the two growth alternatives. The results showed how the biphasic alternative was preferable to the conventional alternative and how the use of the monophasic pattern would result in an overly optimistic view of stock status (+40% in SSB/SSBtarget and −35% in F/Ftarget compared to the biphasic pattern), thereby increasing the risk of overfishing.

A high‐impact meso‐beta vortex in the Adriatic Sea

AbstractOn the evening of November 12, 2019, an exceptional high tide – the second‐highest in the ranking since sea‐level data have been recorded – hit the city of Venice in northern Italy and its entire lagoon, damaging a large part of its historical center. A small warm‐core mesoscale cyclone, which formed in the central Adriatic Sea and intensified during its northwestward movement toward the Venice lagoon, was responsible for the event. The cyclone was preceded by intense northeasterlies (Bora) in the northern Adriatic, which turned to southeasterlies (Sirocco) and then southwesterlies after its passage. Simulations with different initialization times were carried out with the Weather Research and Forecasting (WRF) model. Simulation results show a strong sensitivity to the initial conditions, since the track (and strength) of the cyclone was determined by the exact position of an upper‐level potential vorticity (PV) streamer. The factors responsible for the cyclone development and its characteristics are also investigated. The pre‐existence of positive low‐level cyclonic vorticity, associated with the convergence of the Sirocco and Bora winds in the central Adriatic, made the environment favorable for cyclone development. Also, the interaction between the upper‐level PV anomaly and the low‐level baroclinicity, created by the advection of warm, humid air associated with the Sirocco, was responsible for the cyclone's intensification, in a manner similar to a transitory (stable) baroclinic interaction at small horizontal scales. Sensitivity experiments reveal that convection, latent heat release and sea‐surface fluxes did not play a significant role, indicating that this cyclone did not show tropical‐like characteristics, notwithstanding its low‐level warm core. Thus, the warm‐core feature appears mainly as a characteristic of the environment in which the cyclone developed rather than a consequence of diabatic processes. Lastly, the cyclone does not fall into any of the existing categories for Adriatic cyclones.

Diet and feeding of juvenile common two-banded sea bream, Diplodus vulgaris (Teleostei: Sparidae), in the eastern central Adriatic Sea

Abstract The diet and feeding of juvenile common two-banded sea bream, Diplodus vulgaris, in the eastern central Adriatic Sea was studied to better understand local ecosystem dynamics in this region. Stomach contents of 140 individuals with total length (TL) between 22 and 106 mm, collected by small beach seines from February to November, were analysed. Food items identified in stomachs belonged to 16 prey groups: Copepoda, Gastropoda, Teleost eggs, Ostracoda, Polychaeta, Bivalvia, unidentified Crustacea, Amphipoda, Decapoda, Cumacea, Echinoidea, Anisopoda, Euphausiacea, Mysidacea, Branchiopoda and Isopoda. Overall, planktonic copepod crustaceans were the most important prey group (percentage index of relative importance, %IRI = 78.9), followed by gastropods (%IRI = 14.9). All other prey groups had much lower %IRI values and thus were of less importance. Fish size was an important factor influencing food composition. Planktonic copepods were the most important prey in juveniles of smaller sizes (up to 76 mm TL), whereas large-sized juvenile individuals (>76 mm TL) mainly consumed benthic prey, such as gastropods, polychaetes and bivalves. Feeding intensity was very high as indicated by the low vacuity index.

First record of neonatal sandbar shark Carcharhinus plumbeus (Nardo, 1827) (Carcharhiniformes: Carcharhinidae) from the Southern Adriatic Sea

This paper is describing a new finding of Carcharhinus plumbeus (Nardo, 1927) caught at the insular shelves off the Sazan Island at the depth of 120 m, which is the southernmost record for a sandbar shark in the Adriatic Sea. The individual had a partially healed umbilical scar and is considered as neonatal. Examined shark appeared in good body condition with showed no macroscopic signs of diseases or macroscopic parasites. Detailed morphometric measurements are compared with four neonate and juvenile specimens from the north and central Adriatic Sea and are provided in the paper. Despite it is not possible to establish a certain conclusion on whether our specimen was born in the studied area or elsewhere, presented finding provides the very first evidence that neonatal sandbar sharks can be found along the coast of Albania. Knowing the exact locations and movements of both neonates and juveniles is of high importance for the effective long-term in-situ conservation.

First Evidence of Microplastics in the Yolk and Embryos of Common Cuttlefish (Sepia officinalis) from the Central Adriatic Sea: Evaluation of Embryo and Hatchling Structural Integrity and Development.

Once they reach the aquatic environment, microplastics (MPs) are accidentally ingested by aquatic biota, thus entering the food chain with possible negative effects. The present study investigated, for the first time, MP presence in cuttlefish (Sepia officinalis) eggs and their association with embryonic development. Cuttlefish eggs were sampled from four different sites along the Marche region (Senigallia, Ancona, Numana, and San Benedetto del Tronto). Embryo and hatchling biometric parameters were evaluated and the internal structural integrity was examined through histological analysis. MPs were detected and characterized in embryos and yolk samples. MPs were identified in all sites (size < 5 µm), however, their presence has not been associated with an impairment of either embryo or hatchling internal structures. Noteworthy, the highest number of MPs (in both yolk and embryo samples) were found in Numana (37% of the total amount), where the lowest hatchling size was observed. On the other hand, the highest embryo mantle length was associated with the lowest number of MPs detected (9%) in Ancona. Overall, only MP fragments and sphere types (74 and 26%, respectively) were observed, and the most frequent polymers were Polyvinyl chloride (52%), Polypropylene, and Cellulose acetate (15% both). Further studies are needed to assess the possible MP effects on the yolk quality and assimilation.

Vulnerability of the Small-Scale Fishery to Climate Changes in the Northern-Central Adriatic Sea (Mediterranean Sea)

Climate change is altering the functioning of ecosystems and species distribution worldwide, with negative impacts on human activities, including fisheries. The Adriatic Sea is an extremely productive area for fisheries, due to the strong outflow of nutrients from rivers and the periodic mixing of nutrients from the Mediterranean. However, the Adriatic Sea is also a semi-closed basin, where species do not have the ability to move to higher latitudes to avoid warming of the waters. Climate change acts on biodiversity in a variety of ways, such as causing changes in the trophic network—favoring the intake of thermophilic alien species, often in competition with local species—and altering the biological cycles of acclimatized marine species to temperate–cold climates. These problems become critical factors for the survival of species and for fisheries relying on these resources. Within this context, to have estimates of possible modifications of the nektonic community in the near future could be quite useful for preparing adaptation plans. In this paper, using Maximum Entropy models under RCP 4.5 and 8.5 scenarios, we estimated the future habitat suitability for a set of marine nektonic species of different thermal affinity (e.g., cold, temperate and warm species) within GSA17 (Northern and Central Adriatic Sea), among the most productive—and most exploited—areas of the Mediterranean Sea. This study shows how, at the current pace, climate change could modify marine ecosystems to the extent that future habitat suitability will decrease for nearly half of the species considered, with a decrease in landings from 13.5 to 86.9%, depending on the scenario. Only for the blue crab Callinectes sapidus has an increase in habitat suitability been observed. For most of the species considered, temperature was the most important variable to explain the probability of relative presence within the GSA17. On the other hand, GSA17 climatic conditions in the near future under the tested scenarios could become a suitable environment for tropical species, which could find here a suitable habitat, at least in terms of thermal features. Results of the present study can help the management of fishery resources and local markets in the near future, providing information to predict changes in the composition of the aquatic community and draw up management plans that take into account the effects of climate change.

Seasonal Trophic Ecology and Diet Shift in the Common Sole Solea solea in the Central Adriatic Sea

The common sole, Solea solea, is one the most important commercial species in Europe and, within the Mediterranean, the Adriatic basin is the most crucial area for its production. Although the species is overexploited in the basin, data on its trophic ecology are fragmentary, even though this is one of the most important features within the Ecosystem Approach to Fishery. Here, we analysed temporal variations in the feeding ecology of the species by using an integrated approach of stomach contents and stable isotope analyses coupled with the analysis of some condition indices such as the gonadosomatic and the hepatosomatic indices. Changes in diet and trophic level across the years in adult females were clearly linked to the different energetic requirements facing reproduction. Temporal changes throughout the year were mainly related to changes in food availability. This study confirms the opportunistic behaviour of this benthophagous species and its role as a mesopredator, opening new perspectives for further investigations on the effects of the overexploitation of this important fishery resource on the marine trophic web.

Architecture and tube structure of Sabellaria spinulosa (Leuckart, 1849): Comparison with the Mediterranean S. alveolata congener.

The Atlantic-Mediterranean polychaete Sabellaria spinulosa (Leuckart, 1849) lives in agglutinated tubes forming discrete reef-like bioconstructions on shallow-water bottoms beaten by waves where sediment particles are constantly resuspended. Tubes are built with sand grains glued by a proteinaceous cement. Analyses of a S. spinulosa reef sample of this worm collected off the Casarza coast (central Adriatic Sea) allowed the description of its tube architecture and gluing modality. The tube consists of three layers of agglutinated sand: (a) a thin inner layer with sandy particles arranged side by side with a flat side facing the tube lumen (b) a thick middle layer with larger isodiametric and squat grains with empty pores in between; and (c) a thin discontinuous outer layer of heterometric clasts, prevalently large and flat, diverging towards the opening. This fits the general tube construction known for S. alveolata and in general for tubes of the sabellariidae family, but compared to Sabellaria alveolata, S. spinulosa possesses a smaller tube with a wall about 1/3 thick; the agglutinated sandy elements are finer, and some number of muddy particles participates in the tube construction. Morphological and epifluorescence observations revealed that biocement portions are irregularly and haphazardly distributed compared with those of S. alveolata that consist of drops and strips of glue carefully placed. Adjacent tubes leave empty interspaces in between them only locally filled by loose sand, extremely reduced to absent in S. alveolata.

A rare occurrence of reversal in the four-spotted megrim Lepidorhombus boscii (Risso 1810) (Pleuronectiformes: Scophthalmidae) in the central Adriatic Sea.

One reversal dextral (right-sided) specimen occurred in the sample of 1070 individuals of four-spotted megrim Lepidorhombus boscii caught in the central Adriatic Sea from July 2020 to June 2021. This is the first documented occurrence of reversal in this species in the Adriatic Sea. Besides reverse symmetry, the individual showed similar morphological and morphometric characteristics as non-reversed individuals.

Accounting for environmental and fishery management factors when standardizing CPUE data from a scientific survey: A case study for Nephrops norvegicus in the Pomo Pits area (Central Adriatic Sea).

Abundance and distribution of commercial marine resources are influenced by environmental variables, which together with fishery patterns may also influence their catchability. However, Catch Per Unit Effort (CPUE) can be standardized in order to remove most of the variability not directly attributable to fish abundance. In the present study, Generalized Additive Models (GAMs) were used to investigate the effect of some environmental and fishery covariates on the spatial distribution and abundance of the Norway lobster Nephrops norvegicus within the Pomo/Jabuka Pits (Central Adriatic Sea) and to include those that resulted significant in a standardization process. N. norvegicus is a commercially important demersal crustacean, altering its catchability over the 24-h cycle and seasons according to its burrowing behavior. A historically exploited fishing ground for this species, since 2015 subject to specific fisheries management measures, is represented by the meso-Adriatic depressions, which are also characterized by particular oceanographic conditions. Both the species behaviour and the features of this study area influence the dynamics of the population offering a challenging case study for a standardization modelling approach. Environmental and catch data were obtained during scientific trawl surveys properly designed to catch N. norvegicus, thus improving the quality of the model input data. Standardization of CPUE from 2 surveys from 2012 to 2019 was conducted building two GAMs for both biomass and density indices. Bathymetry, fishing pressure, dissolved oxygen and salinity proved to be significant drivers influencing catch distribution. After cross validations, the tuned models were then used to predict new indices for the study area and the two survey series by means of informed spatial grids, composed by constant surface cells, to each of which are associated average values of environmental parameters and specific levels of fishing pressure, depending on the management measures in place. The predictions can be used to better describe the structure and the spatio-temporal distribution of the population providing valuable information to evaluate the status of such an important marine resource.

Looking for a Simple Assessment Tool for a Complex Task: Short-Term Evaluation of Changes in Fisheries Management Measures in the Pomo/Jabuka Pits Area (Central Adriatic Sea)

A Before–Intermediate–After Multiple Sites (BIAMS) analysis, namely a modified version of the Before–After–Control–Impact (BACI) approach, was used to evaluate the possible effects of fishery management measures implemented in the Pomo/Jabuka Pits area, a historically highly exploited ground for Italian and Croatian fisheries, whose impact may have contributed over the years to the modification of the ecosystem. Since 2015, the area was subject to fishing regulations changing the type of restrictions over time and space, until the definitive establishment in 2018 of a Fishery Restricted Area. These changes in the regulatory regime result in complex signals to be interpreted. The analysis was carried out on abundance indices (i.e., kg/km2 and N/km2) of five commercially or ecologically relevant species, obtained in the period 2012–2019 from two annual trawl surveys. BIAMS was based on the selection of a Closure factor, declined in three levels (i.e., BEFORE/INTERMEDIATE/AFTER) and accounting for regulation changes in time, and on three adjacent strata (i.e., “A”, “B”, and “ext ITA”) a posteriori determined according to the latest regulations. BIAMS allowed us to identify early effects (i.e., changes in abundances), overcoming the unavailability of a proper independent control site; furthermore, the selection of adjacent strata allowed the inference of possible interactions among them.

Submarine Outfalls of Treated Wastewater Effluents are Sources of Extensively- and Multidrug-Resistant KPC- and OXA-48-Producing Enterobacteriaceae in Coastal Marine Environment.

The rapid and ongoing spread of carbapenemase-producing Enterobacteriaceae has led to a global health threat. However, a limited number of studies have addressed this problem in the marine environment. We investigated their emergence in the coastal waters of the central Adriatic Sea (Croatia), which are recipients of submarine effluents from two wastewater treatment plants. Fifteen KPC-producing Enterobacteriaceae (nine Escherichia coli, four Klebsiella pneumoniae and two Citrobacter freundii) were recovered, and susceptibility testing to 14 antimicrobials from 10 classes showed that four isolates were extensively drug resistant (XDR) and two were resistant to colistin. After ERIC and BOX-PCR typing, eight isolates were selected for whole genome sequencing. The E. coli isolates belonged to serotype O21:H27 and sequence type (ST) 2795, while K. pneumoniae isolates were assigned to STs 37 and 534. Large-scale genome analysis revealed an arsenal of 137 genes conferring resistance to 19 antimicrobial drug classes, 35 genes associated with virulence, and 20 plasmid replicons. The isolates simultaneously carried 43–90 genes encoding for antibiotic resistance, while four isolates co-harbored carbapenemase genes blaKPC-2 and blaOXA-48. The blaOXA-48 was associated with IncL-type plasmids in E. coli and K. pneumoniae. Importantly, the blaKPC-2 in four E. coli isolates was located on ~40 kb IncP6 broad-host-range plasmids which recently emerged as blaKPC-2 vesicles, providing first report of these blaKPC-2-bearing resistance plasmids circulating in E. coli in Europe. This study also represents the first evidence of XDR and potentially virulent strains of KPC-producing E. coli in coastal waters and the co-occurrence of blaKPC-2 and blaOXA-48 carbapenemase genes in this species. The leakage of these strains through submarine effluents into coastal waters is of concern, indicating a reservoir of this infectious threat in the marine environment.

Impacts of Sea Bottom Temperature on CPUE of European Lobster Homarus gammarus (Linnaeus, 1758; Decapoda, Nephropidae) in the Eastern Adriatic Sea

The study describes recent decadal changes (2008–2017) in the landing biomass, fishing effort and CPUE (kg/day) data of European lobster Homarus gammarus in the eastern Adriatic Sea region, and relates these changes to increases of sea bottom temperatures detected at long-term in situ stations and modelled by an ocean numerical model (ROMS, Regional Ocean Modelling System). Modelling results were further used to quantify spatial and temporal differences of bottom temperature changes over different fishing zones. Trends of sea bottom temperature were positive and statistically significant between stations. Temporal trends of landing, effort and CPUE were also positive and significant for the northern Adriatic. Correlation analysis was used to test the relationship between winter and spring sea bottom temperatures and CPUE data of H. gammarus, separately for the northern and central Adriatic Sea, resulting in statistically significant correlations for both areas. Whether the increased CPUE in the northern Adriatic is due to increased abundance or catchability is discussed. The observed temperature changes likely reflect climate system changes recognised at the regional level and as such, lobster management measures will need to be revised and updated in the future.

A Simplified Approach to Modeling the Dispersion of Mercury from Precipitation to Surface Waters—The Bay of Kaštela Case Study

Wet deposition is the main source of mercury (Hg) from the atmosphere to the Earth’s surface. However, the processes that govern the dispersion of deposited Hg in seawater are currently not well understood. To address this issue, total mercury (THg) concentrations in surface seawaters and precipitation were determined on a monthly basis in the Bay of Kaštela (Central Adriatic Sea). Following the assumption that deposited THg is diluted in the seawater bulk due to mixing processes, an exponential decay-like model was developed and the wet deposition of THg was normalized based on periods between precipitation events and seawater sampling. Normalized wet deposition of THg showed significant correlation with the THg gradient in surface seawater after removal of an outlier. To explain the observed outlier, further data normalization included wind data to account for enhanced seawater mixing due to strong winds. Wind-normalized THg deposition of all datapoints showed significant correlation with the THg gradient in surface seawater. The correlation showed that the THg gradient in surface seawater of 0.378 pg L−1 m−1 corresponds to THg wet deposition of 1 ng m−2 after including the influence of wind speed on seawater mixing.

New records of recently described Zebrus pallaoroi (Actinopterygii: Gobiiformes: Gobiidae) with notes on its morphology, ecology, and molecular identification

The family Gobiidae represents the species-richest family of fishes in the Mediterranean Sea. However, many Mediterranean gobiid species are poorly known with just one or few species records in total. Among those species, the recently described Zebrus pallaoroi Kovačić, Šanda et Vukić, 2021 has been known only from the localities in the species description: the southern Adriatic, northern Ionian, and northern and western Aegean seas. The additional specimens of this species were collected in central and northern Adriatic Sea. The identification was confirmed by morphological and genetic methods. The morphological and preserved coloration characters were compared with the data from the limited type material and the alternative preserved coloration diagnostic character was suggested. The first data on alive and freshly dead coloration are reported. The phylogenetic analysis was performed on sequenced COI, cytochrome b, and rhodopsin genes. The analyzed molecular markers placed Z. pallaoroi in a distinct clade within Zebrus–Millerigobius group. The preference of this species for the very shallow habitat is confirmed and discussed.

Mercury levels in Merluccius merluccius muscle tissue in the central Mediterranean Sea: Seasonal variation and human health risk

In this study we analysed total mercury (THg) levels in European hake (Merluccius merluccius) – an ecologically and commercially important species throughout the Mediterranean – caught in the northern and central Adriatic Sea. To the best of our knowledge, this is the first study evaluating THg levels in hake fillets in relation to ecological (season) and biological (body size, sex, sexual maturity, lipid content) parameters. THg levels in muscle showed no sex-related differences; in contrast, significant season-related differences were found in females, with higher levels in spring-summer compared with autumn-winter. No season-related differences were seen in males. A significant sex effect was found for body size and sexual maturity. Females showed a correlation between THg level and length, THg being significantly higher in mature compared with immature specimens. No significant sex effect was found for muscle lipid content, because a correlation between THg concentration and tissue lipids was found in both sexes.Since the mean THg concentration found in M. merluccius fillets (0.64 ± 0.29 mg kg−1 dry weight; range, 0.20–1.53) was consistently under the level set by EU regulations, this study demonstrates that European hake caught in the northern and central Adriatic is safe for human consumption.