Temporal and spatial biomonitoring of heavy metals in eastern Aegean coastal waters using Amphibalanus amphitrite

This biomonitoring study presents the spatial and temporal distributions of heavy metals in the soft tissues of a major fouling species Amphibalanus amphitrite living on hard substrate at different sites along the eastern Aegean coast. A. amphitrite has been chosen as a strong candidate for monitoring heavy metals. Sediment and seawater samples were also collected to detect their metal contents in order to gain more information on the environmental conditions and possible bioaccumulation patterns. The physico-chemical characteristics of sampling stations have been measured in order to characterize the sampling area. The order of metal concentrations in barnacles, sediment and seawater decreased in the following order Cu > Fe > Zn > Mn > Cd > Cr > Pb > Hg, Fe > Mn > Zn > Cu > Pb > Cr > Hg > Cd and Fe > Zn > Mn > Cu > Pb > Cr > Cd > Hg, respectively. These results showed that barnacles accumulate Cu in a higher degree than both sediment and seawater. Moreover, metal concentrations in barnacle have the potential for use in any future regulatory framework monitoring and eventually controlling ambient metal pollution levels.     

Spatial and temporal variations in nutrient and chlorophyll-a concentrations in the northern East China Sea surrounding Cheju Island

Nutrients, chlorophyll-a (Chl-a), and environmental conditions were extensively investigated in the northern East China Sea (ECS) near Cheju Island during five research cruises from 2003 to 2007. In the eastern part of the study area, surface waters were characterized only by the Tsushima Current Water (TCW) during all five cruises. However, the western surface waters changed with season and were characterized by the Yellow Sea Cold Water (YSCW) in spring, the Changjiang Diluted Water (CDW) in summer, and the Yellow Sea Mixed Water (YSMW) in autumn. In spring and autumn, relatively high concentrations of nitrate and phosphate were observed in the surface waters in the western part of the study area, where vertical mixing brought large supplies of nutrients from deep waters. Changes in wind direction occasionally varied the inflow of the Changjiang plume in summer, clearly causing the annual variation in surface nitrate and phosphate concentrations in summer. In summer, the surface distribution of nitrate and phosphate did not coincide with that of silicate in the study area, which probably resulted from the significant drop in the Si:N ratio in the Changjiang plume since construction of the Three Gorges Dam (TGD). Despite large temporal and spatial variations in surface Chl-a concentrations, depth-integrated Chl-a concentrations exhibited little variation temporally and spatially. In the study area, surface Chl-a concentration did not well reflect the standing stocks of phytoplankton. The vertical distribution of Chl-a showed large temporal and spatial variations, and the main factor controlling the vertical distribution of Chl-a in summer was the availability of nitrate. The thermohaline front may play an important role for accumulation of phytoplankton biomass in spring and autumn.     

Annual and spatial variations of chemical and physical properties in the Ross Sea surface waters (Antarctica)

Temperature, salinity, meltwater percentage, water column stability, dissolved oxygen and nutrients were measured in seawater samples collected at three fixed depths (0, 20, 100 m) in 104 stations located in three different areas of the Ross Sea (Antarctica), during four Italian Antarctic surveys carried out between 1998 and 2006. Nutrient data were used to quantify the nutrient removal, which appears particularly high in 2006, especially in polynya area. The N:P and Si:N disappearance ratios were studied to estimate the dominant phytoplanktonic community. No significant differences in the nutrient drawdown ratio were observed, in fact the N:P ratio was always below the Redfield standard ratio.     

Temporal and spatial variations in the geochemistry of major and minor particulate and selected dissolved elements of Thermaikos Gulf, Northwestern Aegean Sea

The objectives of this study were to examine both spatial and temporal changes of particulate major elements and minor metals, as well as dissolved Mn and Cd, in the waters of Thermaikos Gulf. Collections of water and suspended particulate matter (SPM), as depth profiles (5–8 depths), were undertaken at 10 principal stations, essentially on a N–S traverse of the western side of the Gulf.One of the principal aims of the study was to observe if there was any change in the patterning of the elements between the three occupations of the stations: (a) in September 2001, immediately before the commencement of trawling; (b) in October 2001, whilst fishing was active; and (c) in winter/early spring conditions (February 2002), when fishing was still active, but after a change of river/atmospheric conditions.Bottom (20 m) waters were dominated by sediment resuspension; this was identified by concentration changes in the aluminosilicate elements (e.g. Al, Ti, K, Fe) of the SPM. A two- to three-fold increase occurred between September and October, caused probably by trawling; this was sustained at the offshore stations, in February. During February, the western inshore stations showed little sediment resuspension, caused by extreme winter cooling and the sinking of water. Consequently, a N–S density discontinuity existed at all water depths, which prevented the thermohaline cyclonic circulation from penetrating into the western seaboard of the Gulf. The distribution of dissolved and particulate Mn in the lower waters was due to redox cycling of the element at the benthic boundary; this was more intense in the north, where the organic supply was higher.Biogenic element concentrations and Ca/Al, Si/Al ratios showed no evidence that trawling activity promoted higher biological production. Strong correlations of Co, Cr, Ni and V, with Al and K, showed that these elements were associated strongly with detrital aluminosilicates. However, the variable association of Cd, Pb and Zn, with K (and Al), especially in the upper waters, implied an anthropogenic source derived from the rivers and the city of Thessaloniki. Examination of the Kd's of Cd showed a two-order of magnitude decrease with depth, caused by resuspension and possible advection of relatively unpolluted sediments, into the western Gulf.     

210Po and 210Pb variations in fish species from the Aegean Sea and the contribution of 210Po to the radiation dose

In recent years, there has been increasing interest in the significance of natural radionuclides, particularly (210)Po, in the marine environment. (210)Po, a naturally occurring alpha emitter, accumulates in marine organisms and reflects differences in their diets. In the literature, there is no data for (210)Po and (210)Pb activity concentrations for fish species on the Turkish coast of Aegean Sea. Therefore, in this study, multiple fish species were collected from six stations seasonally on the Turkish coast of Aegean Sea and were analyzed for their (210)Po and (210)Pb content. The (210)Po and (210)Pb concentrations in the fish samples were found to vary from undetectable levels to 499 ± 44 Bq kg(-1) dry weight (dw) and from 1.0 ± 0.3 Bq kg(-1) to 35 ± 4.0 Bq kg(-1) (dw), respectively. There were no significant differences in the activity concentrations of (210)Po and (210)Pb in fish samples between seasons (ANOVA, P>0.05). The highest dose contribution of (210)Po to humans was calculated to be 10,530 μSv year(-1).     

Geochronology and petrology of recent volcanics in the eastern Aegean Sea (West Anatolia and Lesvos Island)

During the lower and middle Miocene the western Anatolia and the eastern Aegean Sea were dominated by a calcalkaline volcanism associated with minor acid and basic volcanics. The basic subcrustal volcanics consist mainly of alkali basalts and hawaiites (9.7–11.9 m.y.), nepheline hawaiites and nepheline trachyandesites (Kula area from 1.1 m.y. to the recent times). The rhyolitic volcanics (12.5 m.y.) derived by a partial melting process in the upper crust (⁸⁷Sr/⁸⁶Sr=0.7121). The calcalkaline suite (16.2–21.5 m.y., mean value⁸⁷Sr/⁸⁶Sr=0.708) shows a trend from latite-andesites to dacites and rhyodacites; a latite andesite system related to a sinking slab of lithosphere and constituted by a mixing of oceanic crust (tholeiite), oceanic sediments and/or tectonic fragments of sialic crust is envisaged.     

Seasonal and interannual variations of nitrate and chloride in stream waters related to spatial and temporal patterns of groundwater concentrations in agricultural catchments

Nitrate concentrations in streamwater of agricultural catchments often exhibit interannual variations, which are supposed to result from land‐use changes, as well as seasonal variations mainly explained by the effect of hydrological and biogeochemical cycles. In catchments on impervious bedrock, seasonal variations of nitrate concentrations in streamwater are usually characterized by higher nitrate concentrations in winter than in summer. However, intermediate or inverse cycles with higher concentrations in summer are sometimes observed. An experimental study was carried out to assess the mechanisms that determine the seasonal cycles of streamwater nitrate concentrations in intensive agricultural catchments. Temporal and spatial patterns of groundwater concentrations were investigated in two adjacent catchments located in south‐western Brittany (France), characterized by different seasonal variations of streamwater nitrate concentrations. Wells were drilled across the hillslope at depths ranging from 1·5 to 20 m. Dynamics of the water table were monitored and the groundwater nitrate and chloride concentrations were measured weekly over 2 years. Results highlighted that groundwater was partitioned into downslope domains, where denitrification induced lower nitrate concentrations than into mid‐slope and upslope domains. For one catchment, high subsurface flow with high nitrate concentrations during high water periods and active denitrification during low water periods explained the higher streamwater nitrate concentrations in winter than in summer. For the other catchment, the high contribution of groundwater with high nitrate concentrations smoothed or inverted this trend. Increasing bromide/chloride ratio and nitrate concentrations with depth argued for an effect of past agricultural pressure on this catchment. The relative contribution of flows in time and correlatively the spatial origin of waters, function of the depth and the location on the hillslope, and their chemical characteristics control seasonal cycles of streamwater nitrate concentrations and can influence their interannual trends. Copyright © 2004 John Wiley & Sons, Ltd.     

Temporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters: influence of the Pearl River outflow and sewage inputs

In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986-2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si=16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.     

Temporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters: Influence of the Pearl River outflow and sewage inputs

In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986–2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si = 16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.     

Rhyolitic fallout and pyroclastic density current deposits from a phreatoplinian eruption in the eastern Aegean Sea, Greece

The Kos Plateau Tuff consists of pyroclastic deposits from a major Quaternary explosive rhyolitic eruption, centred about 10 km south of the island of Kos in the eastern Aegean, Greece. Five main units are present, the first two (units A and B) were the product of a phreatoplinian eruption. The eruption style then changed to `dry' explosive style as the eruption intensity increased forming a sequence of ignimbrites and initiating caldera collapse. The final waning phase returned to phreatomagmatic eruptive conditions (unit F). The phreatomagmatic units are fine grained, poorly sorted, and dominated by blocky vitric ash, thickly ash-coated lapilli and accretionary lapilli. They are non-welded and were probably deposited at temperatures below 100°C. All existing exposures occur at distances between 10 km and 40 km from the inferred source. Unit A is a widespread (>42 km from source), thin (upwind on Kos) to very thick (downwind), internally laminated, dominantly ash bed with mantling, sheet-like form. Upwind unit A and the lower and middle part of downwind unit A are ash-rich (ash-rich facies) whereas the upper part of downwind unit A includes thin beds of well sorted fine pumice lapilli (pumice-rich facies). Unit A is interpreted to be a phreatoplinian fall deposit. Although locally the bedforms were influenced by wind, surface water and topography. The nature and position of the pumice-rich facies suggests that the eruption style alternated between `wet' phreatoplinian and `dry' plinian during the final stages of unit A deposition.Unit B is exposed 10–19 km north of the inferred source on Kos, overlying unit A. It is a thick to very thick, internally stratified bed, dominated by ash-coated, medium and fine pumice lapilli in an ash matrix. Unit B shows a decrease in thickness and grain size and variations in bedforms downcurrent that allow definition of several different facies and laterally equivalent facies associations. Unit B ranges from being very thick, coarse and massive or wavy bedded in the closest outcrops to source, to being partly massive and partly diffusely stratified or cross-bedded in medial locations. Pinch and swell, clast-supported pumice layers are also present in medial locations. In the most distal sections, unit B is stratified or massive, and thinner and finer grained than elsewhere and dominated by thickly armoured lapilli. Unit B is interpreted to have been deposited from an unsteady, density stratified, pyroclastic density current which decelerated and progressively decreased its particle load with distance from source. Condensation of steam during outflow of the current promoted the early deposition of ash and resulted in the coarser pyroclasts being thickly ash-coated. The distribution, texture and stratigraphic position of unit B suggest that the pyroclastic density current was generated from collapse of the phreatoplinian column following a period of fluctuating discharge when the eruptive activity alternated between `wet' and `dry'. The pyroclastic density current was transitional in particle concentration between a dilute pyroclastic surge and a high particle concentration pyroclastic flow. Unidirectional bedforms in unit B suggest that the depositional boundary was commonly turbulent and in this respect did not resemble conventional pyroclastic flows. However, unit B is relatively thick and poorly sorted, and was deposited more than 19 km from source, implying that the current comprised a relatively high particle concentration and in this respect, did not resemble a typical pyroclastic surge.     

Operational Monitoring and Forecasting in the Aegean Sea: System Limitations and Forecasting Skill Evaluation

The POSEIDON system, based on a network of 11 oceanographic buoys and a system of atmospheric/oceanic models, provides real-time observations and forecasts of the marine environmental conditions in the Aegean Sea. The buoy network collects meteorological, sea state and upper-ocean physical and biochemical data. The efficiency and functionality of the various system components are being evaluated during the present pre-operational phase and discussed in this paper. The problem of bio-fouling on optical and chemical sensors is found to be a main limitation factor on the quality of data. Possible solutions to this problem as well as quality control methods that are being developed are also described. Finally, an evaluation of the numerical models is presented through the estimation of their forecasting skill for selected periods.     

Rate of sedimentation in Lake Kinneret,Israel: spatial and temporal variations

The rate of sedimentation in Lake Kinneret was measured over several years by means of sediment traps, in up to seven different locations in the lake. Gross sedimentation rates measured in the sediment traps vary from about 1·5 kg m⁻² a⁻¹ in the deepest part of the lake up to 10 kg m⁻² a⁻¹ near the mouth of the upper Jordan river. The rate of sedimentation near the Jordan's inflow is highly correlated to flow discharge in the river, while in the centre of the lake the seasonal sedimentation pattern is mainly correlated to the bloom period of Peridinium gatunense. During the bloom period of Peridinium gatunense sedimentation rates all over the lake are very similar, indicating that the Peridinium is evenly distributed in the lake. The average suspended sediment discharge of the upper Jordan river flowing into the lake is 41 000 ton a⁻¹.Copyright © 2000 John Wiley & Sons, Ltd.     

Satellite-derived variability of the Aegean Sea ecohydrodynamics

Eight years of AVHRR-derived sea surface temperature (SST) and SeaWiFS-derived surface chlorophyll (Chl) data (1998–2005) are used to investigate key processes affecting the spatial and temporal variability of the two parameters in the Aegean Sea. Seasonal mean SST and Chl maps are constructed using daily data to study seasonal dynamics whereas empirical orthogonal function (EOF) and correlational analysis is applied to the 8-day composite SST and Chl anomaly time-series in order to study the variability and co-variability of the two parameters from subseasonal to interannual time-scales. The seasonal mean fields show that Black Sea cold and chlorophyll-rich waters enter through the Dardanelles Strait and they are accumulated in the north-eastern part of the Aegean Sea, steered by the Samothraki anticyclone. Large chlorophyll concentrations are encountered in the hydrological front off the Dardanelles Strait as well as in coastal areas affected by large riverine/anthropogenic nutrient loads. The SST seasonal mean patterns reveal strong cooling that is associated with upwelling along the eastern boundary of the basin during summer due to strong northerly winds, a process which is not present in the surface chlorophyll climatology. The Chl dataset presents much stronger sub-seasonal variability than SST, with large variations in the phase and strength of the phytoplankton seasonal cycles. EOF analysis of the anomaly time-series shows that SST non-seasonal variability is controlled by synoptic weather variations and anomalies in the north–south wind-stress component regulating the summer coastal upwelling regime. Mean SST and Chl patterns, and their associated variations, are not closely linked implying that Black Sea and riverine inputs mainly control the intra-annual and interannual variability of the surface chlorophyll in the Aegean Sea rather than mixing and/or upwelling processes.     

Controls on spatial and temporal variations in sand delivery to salmonid spawning riffles

Fine sediment infiltration into gravel interstices is known to be detrimental to incubating salmonid embryos. Infiltration into spawning riffles can show large spatial variations at the scale of a morphological unit and over time, with significant implications for embryo survival. Furthermore, some process‐based infiltration studies, and incubation‐to‐emergence models assume that fines are delivered to redds via suspension rather than bedload. This process‐based 12‐month study examined spatial patterns of predominantly sand infiltration into gravels in an upland trout stream, using infiltration baskets. An assessment of Rouse numbers for infiltrated sand indicated that it was transported predominantly as bedload at flow peaks. Clear temporal and spatial patterns existed, with highest rates of infiltration strongly associated with higher discharges (r² = 0.7, p < .05). Seasonal variations in the delivery of different grain sizes were also a feature, with enhanced contributions of 0.5–2 mm sediment during elevated winter flows and 0.125–0.5 mm sediment during spring and summer; the latter is potentially harmful to the later stages of embryo incubation. Clear spatial patterns were also evident across riffles, with highest rates of infiltration tending to occur in areas of lower relative roughness—the areas competent to transport sand for longer periods. Incubation‐to‐emergence models should take into consideration spatial patterns of fine sediment dynamics at the pool–riffle scale, to improve prediction.     

Consistency of wave power at a location in the coastal waters of central eastern Arabian Sea

Ocean Dynamics - Wave energy assessment at a regional scale is required for planning installation of wave energy converters. Based on continuously measured wave data at 14-m water depth in the...     

Quantifying temporal variations in water resources of a vulnerable middle eastern transboundary aquifer system

Freshwater resources in the arid Arabian Peninsula, especially transboundary aquifers shared by Saudi Arabia, Jordan, and Iraq, are of critical environmental and geopolitical significance. Monthly Gravity Recovery and Climate Experiment (GRACE) satellite‐derived gravity field solutions acquired over the expansive Saq transboundary aquifer system were analysed and spatiotemporally correlated with relevant land surface model outputs, remote sensing observations, and field data to quantify temporal variations in regional water resources and to identify the controlling factors affecting these resources. Our results show substantial GRACE‐derived terrestrial water storage (TWS) and groundwater storage (GWS) depletion rates of ?9.05 ± 0.25 mm/year (?4.84 ± 0.13 km³/year) and ?6.52 ± 0.29 mm/year (?3.49 ± 0.15 km³/year), respectively. The rapid decline is attributed to both climatic and anthropogenic factors; observed TWS depletion is partially related to a decline in regional rainfall, while GWS depletions are highly correlated with increasing groundwater extraction for irrigation and observed water level declines in regional supply wells.     

Isotopic temporal and spatial variations of tropical rivers in Thailand reflect monsoon precipitation signals

Stable isotopic compositions (δ¹⁸O and d-excess) from 25 rivers in Thailand were analysed monthly during 2013–2015. Results indicated that monsoon precipitation fundamentally influences the river isotopes. The overland flow supplied from monsoon precipitation and human-altered flow regimes produces considerable isotopic variability. Spatial and temporal variations were observed among four principal geographical regions. The seasonality of monsoon precipitation in mountainous Thailand produced large variations in isotopic compositions because most rainfall occurred during the southwest monsoon, and dry conditions prevailed during the northeast monsoon. The northern and northeastern regions are mountainous, highland areas. Low δ¹⁸O values were found in these regions, likely because of altitude effects on precipitation. Conversely, monsoonal precipitation continually supplies rivers in southern Thailand all year round, producing higher and more consistent δ¹⁸O values than in the other regions. The Chao Phraya plain in the central region experienced enrichment of δ¹⁸O river runoff related to evaporation in irrigation systems. Larger catchment areas and longer residence times resulted in more pronounced evaporation effects, producing lower values of d-excess and local river water line slopes compared with precipitation. The isotopic differences between river waters and precipitation were utilized to determine river recharge elevations and water transit time. The methods presented here can be used to explore hydrological interactions in other tropical river basins.     

Long-term variations in the granulometric composition and spatial distribution of bottom sediments in the Northern Caspian Sea

Granulometric analysis was carried out for bottom sediment of the Northern Caspian Sea sampled in 2001. The results of analysis were used to map the spatial distribution of different types of bottom sediments and evaluate their areas. To identify the changes that have taken place in the granulometric composition and spatial distribution of bottom sediments in a transgression period, the obtained materials were compared with data of the previous survey. The main factors of sediments dynamics are shown to be higher continental runoff and sea transgression.     

Seismic properties in the eastern part of the South Aegean volcanic arc

The South Aegean active volcanic arc lies along the 150-km seismic isodepth of a Benioffzone and consists in andesitic, dacitic and rhyolitic volcanoes of an orogenic calc-alkaline type. In the eastern part of the arc there are two main volcanic sites in the Nisyros and Kos islands. High shallow and intermediate depth seismic activity occurs in this volcanic area. Seismological data concerning the 1911–1980 period have been used to investigate seismic properties in that area. Two, distinct regions with different seismotectonic features have been defined. The internal region (Nisyros active volcano and its proximity) is characterized by a shallow, thin seismogenetic layer with abnormally highb-value, locally concentrated stresses, low seismicity and highly heterogeneous structure. These features are probably due to a magmatic body intruded in shallow depths within the crust. The possibility of magma formation in the upper surface of the descending slab or within the upper mantle wedge overlying this slab in the Nisyros-Kos area is herein discussed. On the contrary, the remaining (external) region, including the non-active volcanic island of Kos, is characterized by normal for tectonic shocksb-value, thick seismogenetic layer and high seismicity. It seems that in this region there is not a magmatic intrusion at least in shallow depths within the crust.