Cs baseline levels in the Mediterranean and Black Sea: A cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify ¹³⁷Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured ¹³⁷Cs levels were found to be very low (usually <1 Bq kg⁻¹ wet wt) ¹³⁷Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

(137)Cs baseline levels in the Mediterranean and Black Sea: a cross-basin survey of the CIESM Mediterranean Mussel Watch programme

The common mussel Mytilus galloprovincialis was selected as unique biomonitor species to implement a regional monitoring programme, the CIESM Mediterranean Mussel Watch (MMW), in the Mediterranean and Black Seas. As of today, and upon standardization of the methodological approach, the MMW Network has been able to quantify (137)Cs levels in mussels from 60 coastal stations and to produce the first distribution map of this artificial radionuclide at the scale of the entire Mediterranean and Black Seas. While measured (137)Cs levels were found to be very low (usually < 1 Bq kg(-1) wet wt) (137)Cs activity concentrations in the Black Sea and North Aegean Sea were up to two orders of magnitude higher than those in the western Mediterranean Basin. Such effects, far from representing a threat to human populations or the environment, reflect a persistent signature of the Chernobyl fallout in this area.     

Water mass variation in the Mediterranean and Black Seas

The mass-induced sea level variability and the net mass transport between Mediterranean Sea and Black Sea are derived for the interval between August 2002 and July 2008 from satellite-based observations and from model data. We construct in each basin two time series representing the basin mean mass signal in terms of equivalent water height. The first series is obtained from steric-corrected altimetry while the other is deduced from GRACE data corrected for the contamination by continental hydrology. The series show a good agreement in terms of annual and inter-annual signals, which is in line with earlier works, although different model corrections influence the consistency in terms of seasonal signal and trend.In the Mediterranean Sea, we obtain the best agreement using a steric correction from the regional oceanographic model MFSTEP and a continental hydrological leakage correction derived from the global continental hydrological model WaterGAP2. The inter-annual time series show a correlation of 0.85 and a root mean square (RMS) difference of 15 mm. The two estimates have similar accuracy and their annual amplitude and phase agree within 3 mm and 23 days respectively. The GRACE-derived mass-induced sea level variability yields an annual amplitude of 27 ± 5 mm peaking in December and a trend of 5.3 ± 1.9 mm/yr, which deviates within 3 mm/yr from the altimetry-derived estimate.In the Black Sea, the series are less consistent, with lower accuracy of the GRACE-derived estimate, but still show a promising agreement considering the smaller size of the basin. The best agreement is realized choosing the corrections from WaterGAP2 and from the regional oceanographic model NEMO. The inter-annual time series have a correlation and RMS differences of 0.68 and 55 mm, their annual amplitude and phase agree within 4 mm and 6 days respectively. The GRACE-derived seawater mass signal has an annual amplitude of 32 ± 4 mm peaking in April. On inter-annual time scales, the mass-induced sea level variability is stronger than in the Mediterranean Sea, with an increase from 2003 to 2005 followed by a decrease from 2006 to 2008.Based on mass conservation, the mass-induced sea level variations, river runoff and precipitation minus evaporation are combined to derive the strait flows between the basins and with the Atlantic Ocean. At the Gibraltar strait, the net inflow varies annually with an amplitude of 52 ± 10 × 10⁻³ Sv peaking end of September (1 Sv = 10⁶ m³ s⁻¹). The inflow through the Bosphorus strait displays an annual amplitude of 13 ± 3 ×10⁻³ Sv peaking in the middle of March. Additionally, an increase of the Gibraltar net inflow (3.4 ± 0.8 × 10⁻³ Sv/yr) is detected.     

Inorganic carbon and nutrient fluxes on the Arctic Shelf

Historic data from the Russian-American Hydrochemical Atlas of Arctic Ocean together with data from the TRANSDRIFT II 1994 and TUNDRA 1994 cruises have been used to assess the spatial and inter-annual variability of carbon and nutrient fluxes, as well as air–sea CO₂ exchange in the Laptev and western East Siberian Seas during the summer season. Budget computations using summer data of dissolved inorganic phosphate (DIP), dissolved inorganic nitrogen (DIN) and dissolved inorganic carbon (DIC) gives that the Laptev Sea shelf is a net sink of DIP and DIN of 2.5×10⁶, 23.2×10⁶ mol d⁻¹, respectively, while it is a net source of DIC (excluding air–sea exchange) of 1249×10⁶ mol d⁻¹. In the East Siberian Seas the budget computations give 0.5×10⁶, −11.4×10⁶ and −173×10⁶ mol d⁻¹ (minus being a sink) for DIP, DIN, and DIC, respectively. In summers, the Laptev Sea Shelf is net autotrophic while the East-Siberian Sea Shelf is net heterotrophic, and both systems are weak net denitrifying. The Laptev Sea Shelf takes up 2.1 mmol CO₂ m⁻² d⁻¹ from atmosphere, whereas the western part of the East-Siberian Sea Shelf loose 0.3 mmol CO₂ m⁻² d⁻¹ to the atmosphere. The variability of DIP, DIN and DIC fluxes during summer in the different regions of the Laptev and East Siberian Seas depends on bottom topography, river runoff, exchange with surrounding seas and wind field.     

Contrasting key roles of Ruppia cirrhosa in a southern Mediterranean lagoon: Reservoir for both biodiversity and harmful species and indicator of lagoon health status

The distribution of Ruppia cirrhosa meadow density and its epiphytic organisms in relation with environmental factors were studied in summer 2011 at five stations in the Ghar El Melh lagoon (GML; southern Mediterranean Sea). Eleven epiphytic groups were recognised among which diatoms and dinoflagellates were the dominant groups and greatest contributors to temporal dissimilarity. An overwhelming concentrations of harmful microalgae was recorded, mainly represented by the toxic dinoflagellate Prorocentrum lima with maximal concentrations attaining 6 × 10⁵ cells 100 g⁻¹ of Ruppia fresh weight. The epifauna community accounted for only 1.4% of total epiphyte abundance and was comprised predominantly of nematodes (47.51%), ciliates (32.59%), fish eggs (7.2%) and larvae (4.95%). PERMANOVA analyses revealed a significant spatio-temporal variation of all epiphytic groups (p < 0.01). In this study, R. cirrhosa and its epiphytes were studied as potential early warning indicators of the health status of GML waters.     

Selected trace metals (As,Cd and Hg) distribution and contamination in the coastal wetland sediment of the northern Beibu Gulf,South China Sea

Contamination with As, Cd and Hg, their spatial and temporal distribution are reported from the coastal wetland sediments of the northern Beibu Gulf, South China Sea. The content of As, Cd, Hg and TOC in surface sediments is 8.1 ± 5.8 μg g^?1, 0.08 ± 0.14 μg g^?1, 0.034 ± 0.028 μg g^?1 and 0.45 ± 0.39%, respectively. The mean sedimentation rates are 0.93–1.37 cm year^?1 during 1920s to 2008 determined by ²¹⁰Pb and ¹³⁷Cs dating in three cores. The vertical profiles of As, Cd and Hg content in the cores retrieved from Qin and Nanliu River estuaries show increasing trends during 1985–2008 due to anthropogenic impact caused by local economic development. Locally the surface sediments have potential ecological risk of As to benthos according to the NOAA sediment quality guidelines.     

Spatio-temporal variability of size fractionated phytoplankton on the shelf adjacent to the Ebro river (NW Mediterranean)

The mesoscale distribution and seasonal variation of the size structure of phytoplankton biomass, as measured by chlorophyll a (chl a), was studied in the Ebro shelf area (NW Mediterranean) during three different seasons: autumn, winter and summer. In autumn and summer, when the water column was, respectively, slightly or strongly stratified and nutrient concentrations were low at surface, average total chl a values were 0.31 and 0.29 mg m⁻³, respectively. In winter, the intrusion of nutrients into the photic zone by intense vertical mixing and strong riverine inputs, produced an increase of the total autotrophic biomass (0.76 mg m⁻³). In the three seasons, the main contributor to total chl a was the picoplanktonic (<2 μm) size fraction (42% in winter and around 60% in autumn and summer). The nanophytoplankton (2–20 μm) contribution to total chl a showed the lowest variability amongst seasons (between 29% and 39%). The microplanktonic (>20 μm) chl a size fraction was higher in winter (27%) than in the other seasons (less than 13%). The maximum total chl a concentrations were found at surface in winter, at depths of 40 m in autumn and between 50 and 80 m in summer. The relative contribution of the <2 μm size fraction at these levels of the water column tended to be higher than at other depths in autumn and winter and lower in summer. In autumn and winter, nutrient inputs from Ebro river discharge and mixing processes resulted in an increase on the >2 μm contribution to total chl a in the coastal zone near the Ebro Delta area. In summer, the contribution of the <2 and >2 μm chl a size fractions was homogeneously distributed through the sampling area. In autumn and summer, when deep chl a maxima were observed, the total amount of the autotrophic biomass in the superficial waters (down to 10 m) of most offshore stations was less than 10% of the whole integrated chl a (down to 100 m or to the bottom). In winter, this percentage increased until 20% or 40%. The >2 μm chl a increased linearly with total chl a values. However, the <2 μm chl a showed a similar linear relationship only at total chl a values lower than 1 mg m⁻³ (in autumn and summer) or 2 mg m⁻³ (winter). At higher values of total chl a, the contribution of the <2 μm size fraction remained below an upper limit of roughly 0.5 mg m⁻³. Our results indicate that the picoplankton fraction of phytoplankton may show higher seasonal and mesoscale variability than is usually acknowledged.     

Partial pressure and air–sea CO2 flux in the Aegean Sea during February 2006

Data on the distribution of fCO₂ were obtained during a cruise in the Aegean Sea during February 2006. The fCO₂ of surface water (fCO₂^sw) was lower than the atmospheric fCO₂ (fCO₂^atm) throughout the area surveyed and ΔfCO₂ values varied from ?34 to ?61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO₂ during the winter of 2006. Higher fCO₂^sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO₂^sw.A first estimate of the magnitude of the air–sea CO₂ exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO₂ was also obtained. The air–sea CO₂ fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO₂ at a rate ranging from ?6.2 to ?11.8 mmol m^?2 d^?1 with the shipboard recorded wind speeds and at almost half rate (?3.5 to ?5.5 mmol m^?2 d^?1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO₂.Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO₂ into the deep horizons of the Eastern Mediterranean.     

Magnetic susceptibility and Cs-137 inventory variability as influenced by land use change and slope positions in a hilly,semiarid region of west-central Iran

The objective of this study was to explore the slope position and land use change effects on the variability in magnetic susceptibility and ¹³⁷Cs inventory as the soil redistribution indicators in a hilly semiarid calcareous area in Iran. The selected study area is located in a hilly region with pasture and cultivation land use of Fereydunshahr, Isfahan Province in west-central Iran. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backslope and footslope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm) in an area of 15 × 15 cm. Additional 28 soil samples were collected from the reference site for soil loss and deposition calculations by using the Cs-137 measurement. The results of the study with the use of the Cs-137 technique showed that the average soil loss in the pasture land (46.4 t ha^− 1 yr^− 1) was significantly (p < 0.05) lower than the average soil loss in the cultivated land (80.4 t ha^− 1 yr^− 1). The highest soil loss in both land uses was obtained in the shoulder position, 60.1 and 84.4 t ha^− 1 yr^− 1, respectively, for the pasture and cultivated lands. Moreover, the highest rates of soil deposition was observed in a footslope position in both land uses and they were 34 and 32.4 t ha^− 1 yr^− 1 for the pasture and cultivated lands, respectively. Magnetic susceptibility was significantly (p < 0.05) greater in pasture (χ_lf = 41.51 × 10^− 8 m³/kg) than in the cultivated land (χ_lf = 34.90 × 10^− 8 m³/kg). The pasture land with a lower soil loss rate, indicated significantly higher magnetic susceptibility in all landform positions as compared to that in the cultivated land. The results of the correlation analysis showed that among the studied soil physico-chemical properties, χ_lf (r = 0.83, p < 0.01) in the pasture land had the highest correlation with the Cs-137 inventory. Throughout the non-linear regression analysis, χ_lf was introduced for relating soil parameters and the cesium inventory explained 68% and 79% of the total variability of ¹³⁷Cs in the pasture and cultivated lands, respectively. The results implied that the variability in the magnetic susceptibility within the hillslope is consistent with the variation of the Cs-inventory; and the results thus demonstrate the slope and land use effects on soil redistribution.     

Sea-level changes and shelf break prograding sequences during the last 400 ka in the Aegean margins: Subsidence rates and palaeogeographic implications

The subsidence rates of the Aegean margins during the Middle-Upper Pleistocene were evaluated based on new and historical seismic profiling data. High-resolution seismic profiling (AirGun, Sparker and 3.5 kHz) have shown that (at least) four major oblique prograding sequences can be traced below the Aegean marginal slopes at increasing subbottom depths. These palaeo-shelf break glacial delta sediments have been developed during successive low sea-level stands (LST prograding sequences), suggesting continuous and gradual subsidence of the Aegean margins during the last 400 ka. Subsidence rates of the Aegean margins were calculated from the vertical displacement of successive topset-to-foreset transitions (palaeo-shelf break) of the LST prograding sediment sequences.The estimated subsidence rates that were calculated in the active boundaries of the Aegean microplate (North Aegean margins, Gulfs of Patras and Corinth) are high and range from 0.7 to 1.88 m ka^?1, while the lowest values (0.34–0.60 m ka^?1) are related to the low tectonic and seismic activity margins like the margin of Cyclades plateau. Lower subsidence rates (0.34–0.90 m ka^?1) were estimated for the period 146–18 ka BP (oxygen isotopic stages 6–2) and higher (1.46–1.88 m ka^?1) for the period from 425 to 250 ka BP (oxygen isotopic stages 12/10–8). A decrease of about 50% of the subduction rates in the Aegean margins was observed during the last 400 ka.During the isotopic stages 8, 10, 11 and 12, almost the 50–60% of the present Aegean Sea was land with extensive drainage systems and delta plains and large lakes in the central and North Aegean. Marine transgression in the North Aegean was rather occurred during the isotopic 9 interglacial period. The estimated palaeomorphology should imply fan delta development and sediment failures in the steep escarpments of the North Aegean margins and high sedimentation rates and turbidite sediment accumulation in the basins. It is deduced that the Black Sea was isolated from the Mediterranean during the Pleistocene prior oxygen isotopic stage 5.     

Content and distribution of trace metals in surface sediments from the northern Bering Sea,Chukchi Sea and adjacent Arctic areas

Concentrations of trace metals (Zn, Cr, Cu, V, Cd and Pb), total organic carbon (TOC), black carbon (BC) and their granulometry were examined in 25 surface sediment samples from the northern Bering Sea, Chukchi Sea and adjacent areas. Trace metal concentrations in the sediments varied from 21.06–168.21 mg kg⁻¹ for Zn, 8.91–46.94 mg kg⁻¹ for Cr, 2.69–49.39 mg kg⁻¹ for Cu, 32.46–185.54 mg kg⁻¹ for V, 0.09–0.92 mg kg⁻¹ for Cd, and 0.95–15.25 mg kg⁻¹ for Pb. The geoaccumulation index (I_geo) indicated that trace metal contamination (Zn and Cd) existed in some stations of the study area. The distribution of grain size plays an important role in influencing the distribution of trace metals (Zn, Cr, Cu, V, and Pb) in sediments from the Chukchi Sea and adjacent areas.     

Luminescence dating of the top of a deep water core from the NESTOR site near the Hellenic Trench,east Mediterranean Sea

In the present study, the uppermost 3 cm of muddy, seabed sediment was collected from a deep-sea sediment core, drilled from a water depth of 4 km, near the deepest site of the Mediterranean Sea, outside Pylos, Greece. The core was divided into 7 layer samples, each 3–4 mm thick, in order to get an independent age assessment for each one using luminescence dating; from polymineral coarse grains in the range 30–60 μm. Between 11 and 22 aliquots were measured for each sample using the optically stimulated luminescence, single-aliquot regenerative-dose analysis. The estimated mean equivalent dose values had an uncertainty less than 3% and resulted in optical ages ranging from 3.5 to approximately 5 ka, with uncertainties lying between 5.5 and 7.4%. Multiple-aliquot, thermoluminescence-based, additive-dose, total bleaching approach provided equivalent doses with typical errors of 10–15% and ages in the range of 3.6 and 9.4 ka, with uncertainties up to 17%. Single-aliquot optical ages are shown to be relatively successful, due to their consistency with AMS ¹⁴C radiocarbon ages, obtained from Planktonic foraminifera from the same core. Luminescence dates for the topmost 1.5 cm indicate a substantial mix and post burial disturbance of the surface sediment. Below the topmost 1.5 cm, both luminescent approaches indicate ages which increase smoothly with depth. The concordant OSL and TL age estimates for the sample O5, in conjunction with specific luminescence properties and its major-element geochemical chemistry content, suggest that it was heated during the Santorini volcanic eruption. Deposition rates of 8.6–18.9 cm over 10 ka below the sample O5, provided by optical ages, exhibit an excellent level of agreement with the accumulation rate of 7–18 cm over 10 ka at the sea bottom, already reported for the site under study.     

Late Holocene intermediate water variability in the northeastern Atlantic as recorded by deep-sea corals

The Nd isotopic composition of the aragonite skeleton of fossil deep-sea corals (Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus) located in the northeastern Atlantic at water depths between 635 and 1300 m was investigated to reconstruct changes in the Atlantic mid-depth gyre circulation during the past millennium. The coral εNd values varied systematically from ? 11.8 to ? 14.4 during the past 1500 years, reflecting variations in seawater εNd and thus water mass provenance. Low εNd values (εNd = ? 14) occurred during the warm Medieval Climatic Anomaly (MCA) (between 1000 AD and 1250 AD) and during the most recent period (1950 AD to 2000 AD), interrupted by a period of significantly higher εNd values (~?12.5) during the Little Ice Age (LIA) (between 1350 AD and 1850 AD). One long-lived branching coral even recorded an abrupt systematic rise from low to high εNd values around 1250 AD over the course of its 10-year growth period.These variations are interpreted to result from variable contributions of the subpolar and subtropical Atlantic intermediate water masses, which today are characterized by εNd values of ? 15 and ~?11, respectively. The low εNd values observed during the warm MCA and during recent times imply a strong eastward extension of the mid-depth subpolar gyre (SPG) induced by a dominant positive phase of the North Atlantic oscillation (NAO). During the LIA, water from the subtropical gyre (STG) and potentially from the Mediterranean Sea Water (MSW) propagated further northward, as indicated by the higher coral εNd values. This pattern suggests a negative mean state of the NAO during the LIA, with weaker and more southerly located Westerlies and a westward contraction of the SPG. Variations in the contributions of the two gyres imply changes in the heat and salt budgets at intermediate depths during the past millennia that may have contributed to changes in the properties of North Atlantic inflow into the Nordic Seas and thus deep-water formation.     

Effects of tributyltin at concentrations below ambient levels in seawater on Caprella danilevskii (Crustacea: Amphipoda: Caprellidae)

Hatched juveniles of Caprella danilevskii (Crustacea: Amphipoda) were exposed to one of two concentrations of tributyltin (TBT) (1.1 and 10.7 ng TBT L⁻¹) for 49 d at 20 °C. These concentrations are near or below ambient levels in seawater. In both treatments and control, the survival rate was 100% at maturation, and >85% at the end of the experiments. Females reached maturation at 20 (median) to 21.5 d at instar VII, and repeated spawning 4–5 times during the experiment. The total number of juveniles per female decreased significantly from 39.5 in the control to 24.5 and 17.5 in 1.1 ng L⁻¹ and 10.7 ng L⁻¹ treatments, respectively. An earlier study reported that as the TBT concentration in seawater increased from a 0–10 ng L⁻¹ regime to a 10–20 ng L⁻¹ regime, the number of stations where Caprella spp. could be collected decreased along the coast of the Seto Inland Sea, of Japan. Thus, the present study indicates the possibility that the extremely low concentration of TBT measured in Japanese waters after 2000 lead to a reduction in reproductive success of Caprella spp.     

Mineralogical and geomicrobial examination of soil contamination by radioactive Cs due to 2011 Fukushima Daiichi Nuclear Power Plant accident

Soil contamination by radioactive Cs from Fukushima Daiichi Nuclear Power Plant accident was investigated. Absorption and desorption experiments of Cs were conducted for several phyllosillicates (kaolinite, sericite, montmorillonite, vermiculite, chrysotile and biotite), zeolite and solid organic matter (dead and green leaves). The results confirmed the characteristic sorption and desorption of Cs by these materials. The 2:1 type phyllosilicate, especially, vermiculite and montmorillonite absorbed Cs well. Heated vermiculite for agricultural use and weathered montmorillonite also adsorbed Cs. Leaves also absorbed Cs considerably but easily desorbed it. In summary, the relative capacity and strength of different materials for sorption of Cs followed the order: zeolite (clinoptilolite) > 2:1 type clay mineral > 1:1 type clay mineral > dead and green leaves. Culture experiments using bacteria of both naturally living on dead leaves in Iitate village, Fukushima Pref. and bacterial strains of Bacillus subtillis, Rhodococus erythropolis, Streptomyces aomiensis and Actinomycetospora chlora were carried out. Non-radioactive 1% Cs solution (CsCl) was added to the culture media. Two types of strong or considerable bacterial uptakes of Cs were found in bacterial cells. One is that Cs was contained mainly as globules inside bacteria and the other is that Cs was absorbed in the whole bacterial cells. The globules consisted mainly of Cs and P. Based on all these results, future diffusion and re-circulation behavior of Cs in the surface environment was discussed.     

Glacial–interglacial sediment transport to the Meiji Drift,northwest Pacific Ocean: Evidence for timing of Beringian outwashing

A large sediment deposit known as the Meiji Drift, located in the northwestern Pacific Ocean, is thought to have formed from deep water exiting the Bering Sea, although no notable deep water forms there presently. We determine the terrigenous sources since 140 ka to the drift using bulk sediment ⁴⁰Ar–³⁹Ar and Nd isotopic analyses on the silt-sized (20–63 μm) terrigenous fraction from Ocean Drilling Program (ODP) Site 884 to reconstruct paleo-circulation patterns. There are large changes in both isotopic tracers, varying on glacial–interglacial cycles. During glacial intervals, bulk sediment ⁴⁰Ar–³⁹Ar ages range between 40 and 80 Ma, while Nd isotopic values range from ε_Nd = ? 1 to + 2. During interglacial intervals, sediments become much younger and more radiogenic, with bulk sediment ages falling to 2–15 Ma and Nd isotopic values ranging between ε_Nd = + 5 and + 9. These data and quantitative comparison to potential source rocks indicate that the young Kamchatkan and Aleutian Arcs, lying NW and NE of the Meiji Drift, contribute the majority of sediment during interglacials. Conversely, older source rocks, such as those drained by the Yukon River and northeast Russia are the dominant origin of sediments during glacials. Mixing model calculations suggest that as much as 35–45% of the sediment deposited in the Meiji Drift during glacials is from the Bering Sea. It remains unclear whether thermohaline-type circulation or focussing of Bering Sea flow lead to the glacial–interglacial sediment source changes observed here.     

TEC variations over the Mediterranean before and during the strong earthquake (M = 6.5) of 12th October 2013 in Crete,Greece

In this paper, the total electron content (TEC) data from eight global positioning system (GPS) stations of the EUREF network, provided by IONOLAB (Turkey), were analyzed using discrete Fourier analysis to investigate the TEC variations over the Mediterranean before and during the strong earthquake of 12th October 2013, which occurred west of Crete, Greece. In accordance with the results of similar analyses in the area, the main conclusions of this study are the following: (a) TEC oscillations in a broad range of frequencies occur randomly over an area of several hundred km from the earthquake and (b) high frequency oscillations (f ⩾ 0.0003 Hz, periods T ⩽ 60 m) may point to the location of the earthquake with questionable accuracy. The fractal characteristics of the frequency distribution may point to the locus of the earthquake with higher accuracy. We conclude that the lithosphere–atmosphere–ionosphere coupling (LAIC) mechanism through acoustic or gravity waves could explain this phenomenology.     

Mercury levels in selected bycatch fish species from industrial shrimp-trawl fishery in the SE Gulf of California

Baseline Hg concentration in bycatch fish from the SE Gulf of California were determined in muscle and liver of 19 species. Levels of Hg in muscle were compared with legal limits of this element in national and international legislation. Considering all fish species, mean concentrations in liver (2.458 ± 1.997 μg g⁻¹) were significantly higher (p < 0.05) than in muscle (0.993 ± 0.670 μg g⁻¹). The sequence of averaged Hg concentrations in most ichthyofauna was liver > muscle. Highest level of Hg in muscle (2.556 μg g⁻¹) and liver (7.515 μg g⁻¹) corresponded to Diapterus peruvianus and Ophioscion strabo, respectively. Considering muscle samples, none of the species had levels of Hg above the limit (1.0 μg g⁻¹ wet weight) in the Mexican legislation; with respect to the Japanese (0.4 μg g⁻¹ wet weight) and British (0.3 μg g⁻¹ wet weight) legislations, 26.3% and 31.6% of the species respectively, were above the corresponding limits.     

Geochronological reconstruction of Cs transport from the Coruh river to the SE Black Sea: comparative assessment of radionuclide retention in the mountainous catchment area

The deposition record of ¹³⁷Cs was traced in the SE Black Sea sediments adjacent to the Coruh river mouth in comparison with the earlier studied chronology of ¹³⁷Cs deposition in front of the Danube delta (NW Black Sea). In both cases, the ¹³⁷Cs profiles showed two subsurface peaks attributable to maximum fallout of ‘bomb’ and Chernobyl radionuclides. The Coruh profile revealed a larger contribution of ‘bomb’ ¹³⁷Cs in comparison with the Chernobyl input, suggesting different coverage of NW and SE Black Sea regions with the Chernobyl fallout. The ¹³⁷Cs-derived dating showed that maximum deposition of particulate bound ¹³⁷Cs in sediments adjacent to the Coruh river mouth was delayed for 14 yr relative to date of Chernobyl accident, reflecting a buffer effect of the watershed soils. This transit time is 3 times longer than in the Danube catchment area, indicating a difference in retention processes in these mountainous (Coruh) and lowland (Danube) river basins. The ¹³⁷Cs profile in Coruh sediments showed penetration of ¹³⁷Cs to much greater depth than would be expected from ¹³⁷Cs fallout chronology, suggesting the sediment mixing rate of 1.3 cm² yr⁻¹. This value was used to evaluate deposition chronology of ¹³⁷Cs, applying the model developed for pulse fallout case. Comparing the measured and modelled data has allowed differentiation of the flood-induced discharge of the ¹³⁷Cs-containing suspended matter and the slower transit of eroded soil particles from the contaminated catchment areas. The obtained results may be used for the prediction of period when the pollutants, deposited over the river basins, can reach the Black Sea.     

Sediment PAH: Contrasting levels in the Caspian Sea and Anzali Wetland

A comparative study of 23 PAH congeners in sediment of the Caspian Sea coast and Anzali Wetland was conducted in 2010. Surface sediment was analyzed using chromatography and mass spectrometry. Total PAH concentrations ranged between 212 and 9009 ng g⁻¹ dw. Spatial distribution maps revealed that PAH levels were higher in the coastal areas of the Caspian Sea where oil related activities have been common since 1800’s. Diagnostic ratios analysis indicated that PAHs largely originated from petrogenic processes. PAH toxicity level was assessed using sediment quality guidelines and toxic equivalent concentrations to determine toxic effects on marine organism. Based on these investigations, in our study areas, the probability of toxicity for benthic organisms is “low to medium”. The toxic equivalent concentrations of carcinogenic PAHs varied between 11 and 231 ng TEQ/g; higher total toxic equivalent concentrations values were found in the coastal areas of the Caspian Sea.