Mediterranean Sea Basin Research Articles

Mercury Studies around the Mediterranean Sea Basin: Ten years of Measurements and Modeling results

Only a few years ago the presence of Reactive Gaseous Mercury (RGM) was believed to be almost exclusively the result of anthropogenic emissions and that sustained high RGM concentrations in the MBL were not considered likely. During the past ten years, an in-depth investigation was carried out in the Marine Boundary Layer (MBL) of the Mediterranean Sea to quantify and possibly explain spatial and temporal patterns of Hg-species concentrations. This paper provides an overview of modeling results and atmospheric measurements performed during several cruise campaigns performed aboard the Research Vessel (RV) URANIA of the CNR over the Mediterranean sea basin. RGM concentrations have been modelled using a photochemical box model of the MBL and compared to measured data obtained during the research cruises. The comparison results supports the hypothesis that there are daytime mercury oxidation reactions occurring which have not yet been identified. Major findings of key studies carried out during ten years of ship-borne activities have been highlighted.

Radioactive survey of coastal water and sediments across Alexandria and Rashid coasts

Alexandria and Rashid being part of the Mediterranean Sea basin cities are concerned with the protection of the marine environment of their territorial waters and coasts. One of the major sources of pollution in the surface water and sediments is the radionuclides.The present study is devoted to reliable detection, identification and classification of the radionuclides using the gamma ray spectrometer to measure the density of the radionuclides (i.e. 238U, 232Th, 40K) along the Alexandria and Rashid beaches and try to know the sources of these radionuclides.Surface sediments and sea water samples were collected from Alexandria and Rashid coastal beaches. The results demonstrate that the main source of radiation along the Alexandria and Rashid beaches is the black sands, which is rich in radio-nuclides, supplied by the River Nile during the flooding period in the last 5000years through the Rashid branch of the Nile. These black sands accumulate mostly on the Rashid beach. The sea waves carry part of these black sands to Alexandria beaches westward.The distribution of 40K along the Alexandria coast revealed that, the western area of Al-Max coast was poor in 40K. On the other hand, the eastern area of Alexandria was rich in 40K, there was a wide relationship between the presence of 40K in sediments and the biological density of fauna and flora in the coast. The behavior of 40K in sediments along the Alexandria coast has been detected as non-uniform correlations between the data at different stations reveal significant differences between their radiometric properties. The lower 40K values for seawater have been detected at stations receiving low saline water discharged from inland sources. The salinity affects the behavior of 40K in surface seawater. This was due to the solubility of 40K in seawater.The measured values for 238U and 232Th for seawater are very low.The continuous monitoring of the radio-nuclides is recommended to assure good environment of these beaches because they are bathing beaches of Alexandria, and an important resource as summer resort.

The impact of the Late Holocene coastal changes on the rise and decay of the ancient city of Histria (southern Danube delta)

Histria (Istros) is one of the earliest Milesian colonies founded on the Black Sea coast during the archaic period (7th c. BC). Its remains are located within what is today the Razelm–Sinoe lagoon system which forms the southern part of the Danube Delta. During its 13 centuries of existence, Histria experienced an environment favourable for a prosperous economy (e.g. fishery, farming, grazing, pottery, marine trades) as indicated by numerous archeological finds from both in situ and elsewhere in the Black Sea and Mediterranean Sea basins. Moreover, it benefited from a strategic position on an open-coast, which was easy to defend. Important environmental changes occurred both during and after the existence of the ancient city, and the most significant are related to major shoreline displacement.This study reports Late Holocene coastal landscape changes, from the open-coast stage to the present-day lagoon system, based on numerical age determination of the paleoshorelines, stratigraphic records by cores in lagoons and beach ridges and topographic surveys. A new chronological framework is established which reports younger ages than previously suggested for the coastal morphosedimentary units of the Histria region. Further, the findings shed new light upon the evolution of the southern part of the Danube delta. The results point to the development of an ancient deltaic lobe (Dunavăţ lobe, 2000–1300 BP, associated with the southernmost Danube distributary) which was situated 10–20 km north of the settlement. The lobe was subsequently reworked by waves, providing sediments which were accumulated downdrift (southward) as a continuous beach ridge plain (Saele–Chituc) in front of the city, leading to its isolation from the sea. The abandonment of Histria (7th c. AD) coincides with the decoupling of the city from the open coast as a consequence of the shoreline progradation. The new beach ridge plain (Saele–Chituc) is affected by intense neotectonic movements which led to the recent drowning of its central part and the formation of Sinoe lagoon; the same processes affected the downdrift part of the Dunavăţ lobe and Histria and Nuntaşi Lakes. The new sea-level curve obtained for the Histria region shows relative stability within the last four millennia, with oscillations within 0 to −2 m of the current level. This contradicts the concept of a marine regression (Phanagorian) which is suggested to have occurred during the 1st millennium BC. However, a few areas containing archeological remains are currently below sea-level owing to local neotectonics.

Forest Fires and Resuspension of Radionuclides into the Atmosphere

Problem statement: Forest fires are especially frequent around the Mediterranean Sea basin in the summer period and might be able to release naturally-occurring and man-made radionuclides from plant biomass and inject them into the atmosphere. The impact of this radioactivity on populations was not investigated before. Approach: Radionuclide analysis was performed in plants, in smoke from plant burning and in cigarette smoke to determine radionuclide concentrations by alpha spectrometry. Results: Concentrations of 210Pb and 210Po in trees such as olive trees, showed low concentrations in roots, trunk and leaves and minor translocation of radionuclides from the root to aerial parts. Soil to plant transfer ratios for 210Po and 210Pb in several plants were in the range from 10-4 to 10-2. Radionuclides from atmospheric depositions may be accumulated in plants by foliar uptake and for 210Pb this seems the main pathway, with plant aerial parts displaying 210Po/210Pb ratios around 0.1, which is similar to the radionuclide ratios determined in atmospheric depositions. Experimental burning of wood from several tree species showed enhanced radionuclide concentrations in smoke compared to plant materials. Investigation of 210Po release from tobacco leaves used in cigarettes, showed especially enhanced concentrations of this radionuclide in the cigarette smoke particles. Conclusion: Radionuclide concentrations in cigarette smoke expose the lung tissues of regular smokers to high concentrations of 210Po that were considered carcinogenic. Although radionuclide concentrations in other plants analyzed were generally lower than in tobacco, globally the radionuclide activity in the plant biomass is elevated. Inhaled smoke particles from forest fires are likely to contribute to enhanced radiation doses in the human lung.

Morphokaryological variability and divergence of stargazers (Uranoscopus, perciformes) from the Mediterranean Sea basin: I. Divergence and taxonomic state of the Black Sea Stargazer

Based on museum collections, the variability of morphological characters of stargazers (Uranoscopus, Uranoscopidae) from different seas of the Mediterranean Sea basin have been studied. On the basis of the obtained results and data on the karyological divergence of the previously studied populations, stargazers of the Black Sea are regarded as an independent subspecies, Uranoscopus scaber anostomus, differing from the Mediterranean Sea populations in relatively long ventral fins, whose length usually exceeds half of the head length, the presence in most individuals of not less than 12 pyloric caeca, chromosome polymorphism with 2n = 28–32, NF = 50, and the presence in the karyotype of a pair of marker small metacentric chromosomes. Morphological characters suitable for analysis of morphological divergence of populations of the Mediterranean region have been revealed.

Nawracające zapalenie opłucnej jako wiodący objaw rodzinnej gorączki śródziemnomorskiej

Familial Mediterranean Fever (FMF) is a disease with an autosomal recessive inheritance affecting inhabitants of the Mediterranean Sea basin area. It is the most prevalent fever-inflammatory syndrome manifested by fever episodes, serositis and rash. The symptoms regress spontaneously and between recurrent attacks of fever the child is healthy. Amyloidosis is the most serious complication. A case of a 8 year-old boy, a son of Armenian immigrants, with recurrent pleuritis is presented.

Diamysis cymodoceae sp. nov. from the Mediterranean, Marmora, and Black Sea basins, with notes on geographical distribution and ecology of the genus (Mysida, Mysidae)

Adult male Diamysis cymodoceae sp. nov. are unique within the family Mysidae by having a peculiar furry covering on the postero-lateral portions of the carapace. This phytophilic mysid inhabits meso- to metahaline waters in a wide arch from the Adriatic, Ionian, and Aegean seas in the E Mediterranean, up to the Sea of Marmora, and the SW Black Sea. A supplementary description of D. mecznikowi (Czerniavsky, 1882) from the Black Sea underlines differences between this and the new species. Considerable extensions of known ranges are reported for D. mesohalobia heterandra Ariani & Wittmann, 2000, to the Marmora basin, for D. bacescui Wittmann & Ariani, 1998, to the island of Cyprus, and for D. lagunaris Ariani & Wittmann, 2000, to the island of Crete. First records from the Algarve coast suggest a conjunction between the NE Atlantic and the Mediterranean populations of D. lagunaris. This could point to an indigenous status of the Atlantic populations, whereas the occurrence in (semi-)artificial water bodies may (on the contrary) confirm a previously proposed non-indigenous status. The ecological diversification within the genus Diamysis Czerniavsky, 1882, mainly pertains to preferences for different salinity conditions and different plant substrates. An updated key to the species is given.

Is the distribution of <i>Prochlorococcus</i> and <i>Synechococcus</i> ecotypes in the Mediterranean Sea affected by global warming?

Abstract. Biological communities populating the Mediterranean Sea, which is situated at the northern boundary of the subtropics, are often claimed to be particularly affected by global warming. This is indicated, for instance, by the introduction of (sub)tropical species of fish or invertebrates that can displace local species. This raises the question of whether microbial communities are similarly affected, especially in the Levantine basin where sea surface temperatures have significantly risen over the last 25 years (0.50 ± 0.11 °C in average per decade, P < 0.01). In this paper, the genetic diversity of the two most abundant members of the phytoplankton community, the picocyanobacteria Prochlorococcus and Synechococcus, was examined during two cruises through both eastern and western Mediterranean Sea basins held in September 1999 (PROSOPE cruise) and in June–July 2008 (BOUM cruise). Diversity was studied using dot blot hybridization with clade-specific 16S rRNA oligonucleotide probes and/or clone libraries of the 16S-23S ribosomal DNA Internal Transcribed Spacer (ITS) region, with a focus on the abundance of clades that may constitute bioindicators of warm waters. During both cruises, the dominant Prochlorococcus clade in the upper mixed layer at all stations was HLI, a clade typical of temperate waters, whereas the HLII clade, the dominant group in (sub)tropical waters, was only present at very low concentrations. The Synechococcus community was dominated by clades I, III and IV in the northwestern waters of the Gulf of Lions and by clade III and groups genetically related to clades WPC1 and VI in the rest of the Mediterranean Sea. In contrast, only a few sequences of clade II, a group typical of warm waters, were observed. These data indicate that local cyanobacterial populations have not yet been displaced by their (sub)tropical counterparts.

Occurrence of Aerosol-Bound Fullerenes in the Mediterranean Sea Atmosphere

This work describes the assessment of a selection of fullerenes including C(60) and C(70) fullerene, N-methylfulleropyrrolidine, C(60) pyrrolidine tris-acid ethyl ester, [6,6]-Phenyl-C(61) butyric acid butyl ester and [6,6]-Thienyl C(61) butyric acid methyl ester, in airborne particulate from the Mediterranean Sea collected during two sampling campaigns from Barcelona to Istanbul and Alexandria, respectively. The analysis of the samples was carried out using a new method based on liquid chromatography coupled to mass spectrometry (LC-MS) presenting sensitivities between 5.4 and 20.9 pg/m(3). A total number of 43 samples covering the different basins of Mediterranean Sea were analyzed. Fullerenes were detected in all analyzed samples and quantifiable concentrations were found in 28 of the analyzed samples. The median of C(60) and C(70) fullerenes aerosol phase concentrations were 0.06 ng/m(3) and 0.48 ng/m(3) respectively for the Mediterranean Sea atmosphere. C(70) fullerene was the most frequently detected compound and also it was found in the higher concentrations for most samples, reaching 233.8 ng/m(3). The modeled back-trajectories disclose that those samples with higher concentrations of fullerenes were related to air masses which had been circulating over regions with an intense industrial activity, but the variability of the C(70)/C(60) ratio suggests multiple different sources. These results are related to the incidental emissions from urban and industrial development, underpinning the need of studying the possible risks associated to carbon nanoparticles in the environment and the need of evaluating the possible consequences of their ubiquitous occurrence.

Accumulation of heavy metals to assess the health status of swordfish in a comparative analysis of Mediterranean and Atlantic areas

During the last few decades, the combined effects of natural and human activities acting on the Mediterranean Sea basin have caused a reduction in the swordfish (Xiphias gladius, L. 1758) population. In this project, we investigated the accumulation of lead (Pb), cadmium (Cd) and mercury (Hg) levels in the Atlantic and Mediterranean populations of swordfish during a five-year survey. In the marine environment, top predators such as swordfish accumulate high concentrations of toxic metals, and thus, potentially incur a high toxicological risk. Furthermore, heavy metals, such as chemical pollutants, have strong long-term effects on fish, and thus, constitute a high risk for the resource and humans that consume it. The aim of this work is to contribute to the assessment of the state of European swordfish population health. We analyzed muscle tissue from 56 specimens captured in Mediterranean and Atlantic areas for trace elements. Mean concentrations of Hg, Cd, and Pb were in the following ranges: 0.66–2.41, 0.04–0.16, and 0.97–1.36mg/kg ww, respectively. These data suggest a need for continuous monitoring to avoid reductions in the population of this fish species of high commercial and ecological interest.

Genetic variation and population structure of Holothuria polii from the eastern and western Mediterranean coasts in Tunisia

Seven populations of Holothuria polii were sampled from the eastern and western Mediterranean coastal waters of Tunisia and screened electrophoretically for genetic variation at 11 allozyme loci. Six among the seven polymorphic loci were out of Hardy–Weinberg equilibrium (HWE) in at least one population. In the same way, the multilocus test showed deviation from HWE in all populations. These populations showed heterozygote deficiency. Genetic variability was relatively low. The number of alleles per locus ranged from 2.09 to 2.27 (average = 2.15), and the observed heterozygosity varied between 0.14 and 0.20 (average = 0.17). The observed overall differentiation among populations was slight but significant, with a mean FST value of 0.024 (P < 0.001). Pairwise FST values reflected the differentiation of the two populations, which were at the margins of the range sampled, from all the others. Our data suggest a population structure consistent with separation by Mediterranean Sea basins that might reflect different local biogeographical zones.

Migratory movements of waterfowl in Central Asia and avian influenza emergence: sporadic transmission of H5N1 from east to west

Waterfowl in the genera Anas and Tadorna are suspected as vectors in the long‐distance transmission of highly pathogenic avian influenza H5N1. The former Soviet Republics of Central Asia are situated at an important migratory crossroads for these and other species of birds that bridges regions where the disease is prevalent. However, waterfowl movements through Central Asia are poorly quantified. In this study, historical data derived from over 80 years of bird ringing are combined with recent satellite tracking data to delineate migration routes, movement chronology and habitat use patterns of waterfowl in relation to H5N1 outbreak locations. Results confirm migratory linkage between breeding and moulting areas in northern Kazakhstan and southern Siberia, with non‐breeding areas in the Caspian, Black and eastern Mediterranean Sea basins, as well as with South Asia. However, unlike the situation in neighbouring regions, most notably western China, H5N1 outbreaks have not been recurrent in Central Asia after they were first reported during summer 2005 and spring 2006. These findings have implications in relation to potential sampling biases, species‐specific variation in migratory behaviour and continuing regional H5N1 transmission risks.

Changes in Storm Frequency in the Mediterranean Sea Region

Abstract Storms in the European part of the Mediterranean Sea Basin are characterized in the paper. Data on storm days comes from the years 1986-2008, from fourteen stations located on the coast and on islands of the Mediterranean Sea (Gibraltar, Valencia, Palma de Majorca, Marseille, Ajaccio – Corsica, Cagliari – Sardinia, Palermo – Sicily, Naples, Luqa – Malta, Thessaloniki, Athens, Souda – Crete, Rhodes Airport – Rhodes and Larnaca – Cyprus). The greatest number of storm days was noted in Corsica (870 - on the average 37,8 per year) and the least in Gibraltar (371 – 16,1). In most of the examined stations storms took place most frequently in the fall (from 19 to 46%). The smallest number of storm days was observed in winter (western and central part of the region) and in summer (eastern part). From a year-to-year analysis of storm days, it was found that their trend, at almost at all the stations, is negative. The strongest negative trend was observed in Valencia, Naples and Cagliari (-8,5 days/10 years). A growing trend, reaching 3 storm days/10 years, was only found in Cyprus.

The record of tidal cycles in mixed silici–bioclastic deposits: examples from small Plio–Pleistocene peripheral basins of the microtidal Central Mediterranean Sea

AbstractThe Pliocene–Pleistocene peripheral marine basins of the Mediterranean Sea in southern Italy, from Basilicata and western Calabria to northern and eastern Sicily, represent tectonically formed coastal embayments and narrow straits. Here, units of cross‐stratified, mixed silici–bioclastic sand, 25 to 80 m thick, record strong tidal currents. The Central Mediterranean Sea has had a microtidal range of ca 35 cm, and the local amplification of the tidal wave is attributed to tides enhanced in some of the bays and to the out‐of‐phase reversal of the tidal prism in narrow straits linking the Tyrrhenian and Ionian basins. The siliciclastic sediment was generated by local bedrock erosion, whereas the bioclastic sediment was derived from the contemporaneous, foramol‐type cool‐water carbonate factories. The cross‐strata sets represent small to medium‐sized (10 to 60 cm thick) two‐dimensional dunes with mainly unidirectional foreset dip directions. These tidalites differ from the classical tidal rhythmites deposited in mud‐bearing siliciclastic environments. Firstly, the foreset strata lack mud drapes and, instead, show segregation of siliciclastic and bioclastic sand into alternating strata. Secondly, the thickness variation of the successive silici–bioclastic strata couplets, measured over accretion intervals of 2 to 3 m and analysed statistically, reveal only the shortest‐term, diurnal and semi‐diurnal tidal cycles. Thirdly, the record of diurnal and semi‐diurnal tidal cycles is included within the pattern of neap‐spring cycles. Differences between these sediments and classical tidal rhythmites are attributed to the specific palaeogeographic setting of a microtidal sea, with the tidal currents locally enhanced in peripheral basins. It is suggested that this particular facies of mud‐free, silici–bioclastic arenite rhythmites in the stratigraphic record might indicate a specific type of depositional sub‐tidal environment of straits and embayments and the shortest‐term tidal cycles.

On the origin of continental precipitation

About 9 out of 10 liters of water evaporated from the oceans every year precipitates back onto oceans. However, the remaining 10% that get transported to continents play an irreplaceable role feeding the land branch of the hydrological cycle. Here we use an objective 3‐D Lagrangian model (FLEXPART) to detect major oceanic moisture source areas and the associated continental regions significantly influenced by each moisture source. Our results reveal a highly asymmetrical supply of oceanic moisture to the continents, with the Northern Atlantic subtropical ocean source impacting the continents considerably more than the large Southern Indian and North Pacific sources. Also, the small Mediterranean Sea and Red Sea basins are important moisture sources for relatively large land areas. The Indian subcontinent receives moisture from six different major oceanic source regions. Future changes in meteorological conditions over the oceanic moisture source regions may have an impact on water availability for many river basins.

Some adaptations of Monodonta turbinata (Born, 1780) (Gastropoda, Prosobranchia, Trochidae) to feeding and habitation in the littoral zone

The basic morphological, ethological, and physiological-biochemical adaptations of Monodonta turbinata to survival in the littoral zone were investigated in this work. Quantitative estimation of myoglobin content in radular tissues of mollusks inhabiting the Mediterranean Sea Basin has been carried out.

Comparison of Source Regions Affecting SO4 2- and NO3 - Concentrations at the Eastern Mediterranean and Black Sea Atmospheres

In this study, source regions of atmospheric sulfate and nitrate in rural areas at the Black Sea and the Mediterranean coasts of Turkey are compared. Stations on the Black Sea and Mediterranean Sea are located at Amasra and Antalya regions, respectively. Source regions of SO4 2- and NO3 - are determined by using potential source contribution function (PSCF). Statistical significance of source regions assigned by PSCF were assured using bootstrapping with 3000 iterations. Source regions affecting sulfate and nitrate concentrations at the Mediterranean and Black Sea regions have some similarities and differences. Emissions from source regions in Russia and Balkan countries affect both the Mediterranean and Black Sea basins.

Climate change evolution of the hydrological balance of the Mediterranean, Black and Caspian Seas: impact of climate model resolution

In this study we have evaluated the ability of the CNRM-ARPEGE CLIMATE V4 general circulation model (GCM) to estimate the present-day hydrological budget components [precipitation minus evaporation over the sea (P − E) and fresh water runoff (R)] over the Mediterranean, Black and Caspian sea basins. Three simulations were performed which were exactly identical except for horizontal resolution, allowing for a unique opportunity to isolate and study the effects of resolution on simulating the hydrological components. Model calculated values of runoff and P − E were compared to a variety of data sources and show that the model’s performance improves significantly with increased resolution, especially in regions with mountainous terrain. Corresponding future climate simulations (following the IPCC A2 scenario) were also performed and indicate that while resolution does not seem to have a significant effect on the qualitative impacts of future climate change on the hydrologic balance, quantitatively the results vary significantly among the models. These results suggests that high resolution global models, or downscaling models such as RCMs, are necessary in order to assess the magnitude of future changes in the hydrological components of these basins.

Molecular evidence of intraspecific variability in Lysidice ninetta (Polychaeta: Eunicidae) in the Mediterranean Sea

A first study of the phylogeography of the polychaete Lysidice ninetta Audouin & Milne- Edwards (Polychaeta: Eunicidae) in the Mediterranean Sea, based on analyses of the molecular mark- ers ITS1 and COI, indicated the occurrence of strong intraspecific variability and possible sibling spe- cies. Here, we report further evidence of the presence of sibling species within L. ninetta, revealed by analysing a new molecular marker (16S rRNA) and supported by preliminary morphological observa- tions. Specimens were collected in association with the seagrass Posidonia oceanica in 6 meadows of the Mediterranean basin; in one of the meadows in which putative siblings co-occurred (Cava meadow off the island of Ischia, Naples, Italy), additional samples were collected for genetic and mor- phological analysis. The mitochondrial region 16S rRNA of 78 specimens revealed 2 haplotypes (nA and nB); morphological characters, associated with these 2 molecular clades were also observed in a sub-set of the analysed specimens of L. ninetta, revealing the presence of 2 morphotypes. The mor- photype termed 'dark', characterised by a typical dark colour pattern on the prostomium and first anterior segments, as well as by black aciculae all along the examined body portion, matching quite well with the description of L. ninetta from the Atlantic type locality, corresponded to haplotype nA. The morphotype termed 'light', with lighter colouration of the prostomium and first anterior segments, and both black and yellow aciculae on the examined body portion, corresponded to haplotype nB, suggesting the existence of a different species. The hypotheses that can be addressed are the follow- ing: (1) only a single new species (the light morph/genotype) is present, while the dark morph corre- sponds to the original L. ninetta species; (2) both morphs/genotypes (dark and light) are new taxa and need to be fully and properly described; and (3) one or both of the species corresponds to previously described species, synonymised by previous authors as L. ninetta. In all cases there is an urgent need for revision of the genus Lysidice and the nominal species in the Mediterranean Sea basin. This is a complex task far beyond the scope of this work.

Coastal and synoptic recirculation affecting air pollutants dispersion: A numerical study

This study examines the spatial distribution of potential recirculation over the East Mediterranean Sea, and the combined effect of synoptic and meso-scale recirculations on plume dispersion in the region. For this purpose, three case studies are performed by the RAMS–HYPACT modeling system, each for a different synoptic scale flow pattern. Both a quantitative measure of the recirculation potential at each grid cell and particle dispersion are calculated. Although the recirculation index is an Eulerian quantity for the wind field and plume dispersion is a manifestation of the Lagrangian behavior of the wind, good correlation is found between the two. Several locations are identified as having high recirculation potential, including southern Cyprus, the coasts of Israel and Lebanon, the eastern slopes of the Judean Mountains and the Haifa Bay in particular. In the latter location, high recirculation potential could be explained by strong interaction between the land–sea surfaces, curvature of the bay and proximity of the Carmel ridge. It is shown that the synoptic and meso-scale recirculations may, under certain conditions, act together and at the same time in determining particle distribution. Under weak synoptic scale flows, particles are recirculated over the entire East Mediterranean Sea basin, returning onshore after a period of 2–3 days to join freshly emitted particles. At the same time, near-shore land–sea breeze effects cause particles to recirculate on smaller time scales of less then one day, sometimes passing as much as three times over the same airshed. A single elevated emission source is shown to have the potential to impair air quality at a coastal strip as long as 100–200 km upon returning onshore.