NE Greece Research Articles

Modelling net primary productivity using near real-time land cover data and soil moisture information

ABSTRACT The objective of this study is to develop a methodological approach to assess ecosystem functioning in terms of carbon uptake and sequestration. To achieve this, a model was developed to forecast Net Primary Productivity (NPP) and tested in a rural area, the Thrace region (NE Greece). Monthly net photosynthesis data from July 2015 to February 2024 was estimated using the MODerate Resolution Imaging Spectroradiometer (MODIS) Aqua MYD17A2H v061 dataset for the study area. This dataset was used as the dependent variable in an Autoregressive Integrated Moving Average (ARIMA) model. The predictive ability of monthly Land Cover (LC) and Soil Moisture (SM) data at various time lags was examined, and variables found to be significant predictors were introduced into the model as external predictors. The study found that crop areas and SM conditions exert the greatest influence on NPP, with areas containing trees exerting a lesser impact. Additionally, NPP was estimated for seven different LC and SM scenarios from March 2023 to February 2024.

A new magmatic crystallization age constraint for the Petrota gabbroic complex from the Jurassic Evros ophiolite, eastern Circum-Rhodope Belt, NE Greece

The Circum-Rhodope Belt is a major tectonic unit that frames both the Rhodope and the Serbo-Macedonian zones of the Alpine orogen in the northern Aegean region. In the eastern part of the Circum-Rhodope Belt, the supra-subduction zone Evros ophiolite is an important crustal component that spans 176 Ma to 169 Ma magmatic activity, which cooled down to 550 °C around 164 Ma according to published radiometric dating. This incomplete ophiolite contains in its upper crustal section gabbroic complexes, to- gether with massive and pillow lavas and dykes. In this contribution, in one of these gabbroic complexes, namely the Petrota gabbroic complex, a cross-cutting basalt dyke was dated to refine the timing of the gabbro crystallization and the temporal spread of the magmatic evolution for the whole complex. The basalt dyke yielded magmatic crystallization age at 164.5±0.93 Ma as derived from U-Pb zircon geochronology. This new crystallization age confirms the previous age for the Petrota gabbro crystallization at 169±2 Ma, but extends the span of the magmatic evolution within 7–8 Myr-lasting time interval (including the analytical errors) for the complex. The latter time interval is comparable in span to the magmatic evolution of another Evros ophi- olite gabbro occurrence at the town of Didymotycho in northeastern Greece.

Campanian Ignimbrite tephra reveals asynchronous vegetation responses to abrupt climate change in the eastern Mediterranean region

The timing and rate of ecosystem response to abrupt climate change is a product of numerous complex interactions between biotic and abiotic drivers. Palaeoecological studies from long sedimentary records, particularly those that span periods of dynamic climate such as the last glacial cycle, can help to contextualise ecosystem responses to climate variability through time. Detailed studies that compare proxy data from multiple sites, with high chronological precision, have the potential to ascribe mutual climate drivers, and, therefore, track spatiotemporal variability in ecosystem responses. Here, we interrogate the vegetation impact of past climate change in the eastern Mediterranean, using three sub-centennially resolved pollen archives from Greece. The widespread Campanian Ignimbrite (CI/Y-5; ca. 39.85 ka BP) tephra marker is used as an isochron to directly correlate pollen records from Ioannina (NW Greece), Tenaghi Philippon (NE Greece), and Megali Limni (NE Aegean). Our results reveal spatiotemporal variability in the timing of vegetation response in the Mediterranean to climate forcing across Heinrich Stadial 4 (40.2–38.3 ka BP), a period of known abrupt climatic change. We identify a decline in tree pollen in all three sites, likely related to the onset of enhanced regional aridity, with vegetation at Tenaghi Philippon responding prior to the CI/Y-5, in contrast to at Megali Limni and Ioannina, where much of the vegetation change occurs following tephra deposition.

Assessment of Groundwater Vulnerability to Seawater Intrusion Using GALDIT, SITE and SIVI Methods in Laspias River Coastal Aquifer System, NE Greece

This paper presents the investigation of groundwater vulnerability to seawater intrusion of the aquifer system in the coastal area of Laspias River, NE Greece, for the year 2023, by applying the GALDIT, SITE and SIVI methods, in the context of the groundwater management of the area. The relevant research works include the collection and analysis of data and information regarding the geological and geomorphological environment, as well as the hydrogeological system of the area. The calculation of the GALDIT, SITE and SIVI indices values is described, and the results from the application of the methods are presented, as well as the design of relevant groundwater vulnerability maps of the study area. This paper concludes with findings and proposals useful for the reliable assessment of the hydrogeological regime of the wider study area.

Insights into fluid evolution and Re enrichment by mineral micro-analysis and fluid inclusion constraints: Evidence from the Maronia Cu-Mo ± Re ± Au porphyry system in NE Greece

Porphyry-epithermal veins hosting Re-rich molybdenite and rheniite (ReS2) from the Maronia Cu-Mo ± Re ± Au porphyry in Thrace, NE Greece, provide new insights into the hydrothermal processes causing extreme Re enrichment. Quartz trace element chemistry (Al/Ti, Ge/Ti), Ti-in-quartz thermometry, and cathodoluminescence imaging reveal multiple quartz generations in consecutive hydrothermal quartz-sulfide veins associated with potassic, sericitic, and argillic alteration. Fluid inclusions in different quartz generations indicate that phase separation and fluid cooling are the main ore-forming processes in the porphyry stage (~ 500 – 350 °C), whereas mixing of a vapor-rich fluid with metalliferous (e.g., Pb, Zn, Au) meteoric water forms the epithermal veins (~ 280 °C). These processes are recorded by trace element ratios in pyrite that are sensitive to changes in fluid temperature (Se/Te), fluid salinity (As/Sb, Co/As), and mixing between fluids of magmatic and meteoric origin (Se/Ge). Highly variable intra-grain δ34S values in pyrite record S isotope fractionation during SO2 disproportionation and phase separation, emphasizing the importance of in situ δ34S analysis to unravel ore-forming processes. High δ34S (~ 4.5‰) values of sulfides are indicative of low SO42−/H2S fluid ratios buffered by the local host rocks and mixing of the magma-derived fluid with meteoric water. The formation of Re-rich molybdenite (~ 6600 ppm) is favored by cooling and reduction of a magma-derived, high-temperature (~400 °C), oxidized, and Re-rich fluid triggering efficient Re precipitation in early veins in the potassic alteration zone. The systematic temporal fluid evolution therefore reveals that coeval cooling and reduction of oxidized Re-rich fluids cause extreme Re enrichment at the Maronia porphyry system.

Assimilating Soil Moisture Information to Improve the Performance of SWAT Hydrological Model

The present work aims to highlight the possibility of improving model performance by assimilating soil moisture information in the calibration and validation process. The Soil and Water Assessment Tool (SWAT) within QGIS, i.e., QSWAT, was used to simulate the hydrological processes within the test basin, i.e., Vosvozis River Basin (VRB) in NE Greece. The model calibration and validation were conducted via SWAT-CUP for a four-year period from 2019 to 2022, in three different ways, i.e., using the traditional calibration process with river flow measurements, using satellite-based soil moisture only in the calibration, and finally incorporating satellite-based soil moisture datasets and calibrating using simultaneously flow and soil moisture information. All modeling approaches used the same set of input data related to topography, land cover, and soil information. This study utilized the recently released global scale daily downscaled soil moisture at 1 km from the Soil Moisture Active Passive (SMAP) mission to generate soil moisture datasets. Two performance indicators were evaluated: Nash Sutcliffe (NS) and coefficient of determination (R2). Results showed that QSWAT successfully simulated river flow in VRB with NS = 0.61 and R2 = 0.69 for the calibration process using river flow measurements at the outlet of VRB. However, comparing satellite-based soil moisture, NS and R2 were considerably lower with an average derived from the 19 subbasins (NS = 0.55, R2 = 0.66), indicating lower performance related to the simulation of soil moisture regime. Subsequently, introducing satellite-derived soil moisture as an additional parameter in the calibration process along with flow improved the acquired average soil moisture results of the 19 subbasins (NS = 0.85, R2 = 0.91), while preserving the satisfactory performance related to flow simulation (NS = 0.57, R2 = 0.66). Our work thus demonstrates how assimilating available satellite-derived soil moisture information into the SWAT model may offer considerable improvement in the description of soil moisture conditions, keeping the satisfactory performance in flow simulation.

Judicial Review of Mufti Decisions Applying Islamic Family Law in Greece

Greece is a unique example of a country member of the Council of Europe that allows for the application of Sharia law by the Mufti on a select part of its citizenry: the members of the Muslim minority in Western Thrace (situated in NE Greece). However, to produce their effects, Mufti decisions need to undergo review and to be declared enforceable by the civil court. The aim of this article is to explore the relevant legal framework arranged in law 4964/2022 and presidential decree 52/2019, whereby the details of such a judicial review are set out. In particular, this article considers the prerequisite of the exequatur to religious adjudication, and then, it goes through all of the levels over which the said review extends, bringing progressively into focus the review of the scope of jurisdiction, the review of compatibility with the Constitution and the European Convention of Human Rights, and the review of some additional issues raised specifically by presidential decree 52/2019 over and above the points just mentioned. A final remark follows in connection with possible errors committed in religious adjudication—errors of law or fact—which remain beyond the reach of the review.

Wind turbine power and land cover effects on cumulative bat deaths

Wind turbines (WT) cause bird and bat mortalities which depend on the WT and landscape features. The effects of WT features and environmental variables at different spatial scales associated to bat deaths in a mountainous and forested area in Thrace, NE Greece were investigated. Initially, we sought to quantify the most lethal WT characteristic between tower height, rotor diameter and power. The scale of interaction distance between bat deaths and the land cover characteristics surrounding the WTs was quantified. A statistical model was trained and validated against bat deaths and WT, land cover, and topography features. Variance partitioning between bat deaths and the explanatory covariates was conducted. The trained model was used to predict bat deaths attributed to existing and future wind farm development in the region. Results indicated that the optimal interaction distance between WT and surrounding land cover was 5 km, the larger distance than the ones examined. WT power, natural land cover type and distance from water explained 40 %, 15 % and 11 % respectively of the total variance in bat deaths by WTs. The model predicted that operating but not surveyed WTs comprise of 377.8 % and licensed but not operating yet will contribute to 210.2 % additional deaths than the ones recorded. Results indicate that among all WT features and land cover characteristics, wind turbine power is the most significant factor associated to bat deaths. In addition, WTs located within 5 km buffer comprised of natural land cover types have substantial higher deaths. More WT power will result in more deaths. Wind turbines should not be licensed in areas where natural land cover at a radius of 5 km exceeds 50 %. These results are discussed in the climate-land use-biodiversity-energy nexus.

Advances in orchid research in East Macedonia (NE Greece) and the importance of current data in furthering our understanding of the orchids’ altitudinal requirements

High-quality data on species distribution and knowledge of species ecology are necessary pre-requisites for their effective conservation. In the European Union, a network of protected areas called the “Natura 2000 network” was set up to conserve the most valuable and threatened species. The Natura 2000 network was supposed to improve rare species conservation, but has it? In this paper, an analysis of data collected from 1 × 1 km grids on the distribution of orchids in East Macedonia (NE Greece) in two consecutive periods of time (before and after 2010), revealed the degree to which a larger data set (including both periods instead of only one) improved our knowledge of the distributions of species and whether the Natura 2000 network can be used as a basis for the conservation of the orchid flora in this area. When the data for the first period and cumulative data for both periods were compared, orchid species richness and density were very similar. However, comparison of the two datasets showed that more orchid taxa were recorded per grid in the first than the second period. However, based on the surveys in the second period, the knowledge on orchid distribution increased significantly. In particular, ten orchid taxa were recorded for the first time in East Macedonia during the second period and significantly more (54.79 % of the total number of species) were recorded. This resulted in a better understanding of their altitudinal requirements. It also confirmed that most of the orchid-rich grid cells in East Macedonia overlap with the Natura 2000 network, which highlights importance of Natura 2000 for orchid conservation.

Assessing Groundwater Evolution with a Combined Approach of Hydrogeochemical Modelling and Data Analysis: Application to the Rhodope Coastal Aquifer (NE Greece)

Assessing the hydrogeochemical evolution of groundwater is a challenging task, which is further exacerbated when considering the multiple geogenic and anthropogenic impacts that affect its quality and the hydraulic interactions between different aquifer bodies. This study combined hydrogeochemical modelling and data analysis to assess this complex hydrogeological regime. Before modelling, the groundwater samples were clustered using a multivariate statistical method (hierarchical cluster analysis (HCA)). Then, the Geochemist Workbench (GWB) software was applied to model the hydrogeochemical groundwater evolution, including the dominant ion exchange process, and to explain the changes in groundwater chemistry towards its flow. The input data consisted of five key parameters from seventy-seven sampling points collected in two periods (accounting for the start and the end of the irrigation period). A data analytical approach based on the optimal mixing ratios between the interacting groundwater systems and recharge inputs was also performed as part of the methodological approach. It revealed a progressively temporal-dependent behaviour of the aquifer system during the irrigation period, resulting in seasonal changes in the hydrodynamic conditions and depletion of the upper aquifer layers. Specifically, the aquifer system was confirmed to undergo cation exchange as the dominant geochemical process that increases calcium concentrations. The complex hydrogeological regime was further evaluated by assessing the mixing ratios of the different aquifer layers. Hence, the aquifer system (bulk samples) was mixed with the irrigation water by 71% and 97% and with the lateral recharge by 76% and 29% for the beginning and at the end of the irrigation period, respectively. Overall, the joint assessments were confirmed by the hydrogeochemical status of the end-members and the modelling approach and explained the sequential changes in groundwater chemistry due to the dominant ion-exchange process and the mixing of different water bodies. The proposed methodological approach proved that it could be used as an exploratory and preliminary method for capturing the temporal dynamics in complex groundwater systems and supporting groundwater resource management.

Nd–Sr–Pb isotopes systematics of the Jurassic Evros ophiolite, eastern Circum-Rhodope Belt, NE Greece

AbstractWe report on the isotopic compositions of the Jurassic supra-subduction zone Evros ophiolite mafic rocks exposed in the eastern Circum-Rhodope Belt of northeastern Greece. These mafic units consist of low-Ti gabbroic and basaltic rocks, whose Nd–Sr–Pb isotopes are compatible with dominant mantle-derived MORB component mixed with a detectable amount of crustal material and/or sediment invoved in their melt source in the subduction zone. These isotopic features are consistent with an intra-oceanic arc origin of the mafic ophiolite rocks, and the Evros ophiolite Nd and Pb isotopes are comparable to those of the counterpart mafic rocks from the Mandritsa unit in Bulgaria.

Use of Edible, Medicinal, and Aromatic Plants in Various Health Disorders: A Cross-Sectional Evaluation among Inhabitants in the Area of Thrace, North-Eastern Greece.

Background: Medicinal and aromatical plants (MAPs) have been historically used as traditional remedies in many cultures in Europe and globally. The aim of this study was to evaluate the use of MAPs in various health disorders in association to dietary habits and other lifestyle factors among residents in Thrace, NE Greece. Methods: Data were collected through anonymous and voluntary responses to a structured online questionnaire, via convenience (snowball) sampling. Results: The 561 responders (age: 39.7 ± 11.6 y) were mostly female (59.7%), with higher education (69.8%), working as state or private employees (55.4%), and having low/medium income (77.1%). Overall, more than 70% were using MAPs in various symptoms and common health disorders, such as chamomile against common cold and the flu. More than 20 different MAPs were being used in smaller frequencies against various conditions. Key contributing factors to the consumption of MAPs were sex (female over male), employment (employed vs. unemployed), education (higher education vs. lower) and higher Body Mass Index (overweight and obese vs. normal), while consumption of fruit, fish, and vegetables was mainly associated with the use of MAPs as common items of diet and in health disorders. Conclusions: The use of MAPs as part of the diet and as traditional remedy is present in the examined population, while particular choices seem to be affected by sociodemographic and lifestyle factors.

Geothermal resources assessment using temperature–depth relationships in the fault-controlled hydrothermal system of Aristino-Traianoupolis area, Northern Greece

Aristino-Traianoupolis area hosts one of the most significant water-dominated low-temperature geothermal fields in Greece. It is located on the southwestern uplifted margin of the Tertiary Evros Delta molassic basin, 10 km east of the town of Alexandroupolis (Thrace, NE Greece). The upper hydrothermal system of the Aristino Geothermal Field (AGF), one of the most promising in continental Greece, contains fluids with temperatures ranging from 51 to 99 °C, within a series of overlapping aquifers at very low depths (100–430 m). The main geothermal anomaly for temperatures higher than 90 °C covers an area of 6 km2, to a maximum prospected depth of 500 m below ground surface. The scattered regional anomaly exceeds 50 km2 and is characterized by excessively high and abruptly changing thermal gradient (42 to 450 °C/km) and heat flow (80–800 mW/m2), that are both typical of a fault-controlled hydrothermal system. Since 1993, the AGF has undergone non-systematic geothermal investigation, with emphasis on low-depth (100–500 m) drilling. This paper provides, for the first time, a synthetic and detailed evaluation of all available temperature data gathered in the last 25 years. The steady-state temperature logs reveal the dominant role of conduction for the upper geothermal system, accompanied, in most cases, by rapidly changing and abnormally high thermal gradients (100–450 °C/km), triggered, most probably, by a deeper system of higher temperature. This hypothesis is also supported by the applied chemical geothermometers, which suggest initial fluid temperatures at 140–150 °C, the hydrochemical characteristics of the fluids hosted in the deeper and most promising investigated reservoir (ignimbrite) of the upper system, and the extrapolated temperatures from the conductive temperature–depth profiles. The lower widespread medium enthalpy hydrothermal system should extend at depths 500–1000 m within volcanics and the expected Eocene limestones and basal clastic series of the Tertiary sequence that have filled the basin. Nevertheless, these assumptions need to be verified by appropriate investigations and new drillings at depths greater than 600–700 m, which would confirm the presence of a productive medium enthalpy reservoir.

Assessment of a Coastal Aquifer in the Framework of Conjunctive Use of Surface Water and Groundwater—The Case of the River Nestos Western Delta, NE Greece

This paper presents research regarding the assessment of the hydrogeological system of the River Nestos Western Delta, NE Greece, during the period of 2019. The procedure included the collection and analysis of relevant hydrological and hydrogeological data concerning the aquifer system of the study area. Specifically, groundwater level measurements and sampling were carried out in a monitoring well network in the shallow unconfined and the deep confined aquifers of the study area, respectively; and surface water sampling was conducted from the River Nestos at selected locations in each of the main drainage canals, as well as in lagoons of the study area; followed by analysis and processing of the relevant chemical analyses results. Finally, piezometric, hydrochemical maps and diagrams were constructed to augment the evaluation of results and the assessment of the system. The present study contributes to the development and management of water resources in the River Nestos Delta area by providing insight into the hydrodynamic and hydrochemical status of the system based on comprehensive contemporary data that can support and justify the compilation of realistic measurements. The conjunctive management of the surface and groundwater in the study area can improve the quantitative and qualitative characteristics of the water. The water level in piezometric maps varies from −4 m up to 16 m for both time periods (May 2019 and October 2019). Moreover, the maximum values of EC are 2700 μS/cm and 2390 μS/cm for the confined and unconfined aquifer systems, respectively. The maximum values of Cl− concentrations are 573.89 mg/L for the confined aquifer system and 514.73 mg/L for the unconfined aquifer system for both time periods (May 2019 and October 2019).

Physical Activity, Body Mass Index (BMI) and Abdominal Obesity of Pre-Adolescent Children in the Region of Thrace, NE Greece, in Relation to Socio-Demographic Characteristics.

This study aimed to explore the prevalence of overweight, obesity, and abdominal obesity, and define predictive factors of their occurrence among pre-adolescents in the region of Thrace, NE Greece. A secondary aim was to record physical activity at different times (schooldays, weekends, holidays) and explore associations with characteristics such as gender, overweight and obesity, and socio-demographic conditions. A cross-sectional study was conducted involving children aged 11–12 years. Participating children were measured for height, weight, and waist circumference, and their parents answered a questionnaire. In total, 1929 children were included. Prevalence of overweight was 31.5%, prevalence of obesity 17%, and only 1% of children were underweight. Abdominal obesity was detected in 20.3% of the sample. Overweight and obesity were more frequent in males, who also had higher mean values of Body Mass Index-for-age z-scores (BMIaz) and Waist-to-Height ratio (WtHR). Obesity rates were higher among those not participating in physical activities; however, no significant difference was observed between normal-weight, overweight and obese children in the time spent for organized athletic activities or free play. Logistic regression analysis showed that the probability for overweight/obesity was higher in boys (OR = 1.39, 95% CI = 1.16–1.66) and lower in children whose fathers had a higher educational level (OR = 0.75, 95% CI = 0.60–0.93). The probability for abdominal obesity was also higher in boys (OR = 1.37, 95% CI = 1.10–1.72) and lower in children participating at least one hour/day in an organized physical activity (compared to those with no physical activity (OR = 0.66, 95% CI = 0.51–0.85), and whose father was exercising at least 1–2 times/week (OR = 0.76, 95% CI = 0.591–0.98). In conclusion, the prevalence of overweight and obesity among pre-adolescents in NE Greece was estimated at 48.5%. This is associated with the male gender and not participating in physical activities. The educational level and exercise habits of the father (but not of the mother) affect the probability of obesity and abdominal obesity, respectively.

Comparison between Calculation and Measurement of Total Sediment Load: Application to Streams of NE Greece

Sediment transport and stream discharge are two of the natural procedures which affect the hydromorphological profile of a watercourse. Measurements of water discharge, bed load transport rate and suspended sediment concentration were conducted in Kosynthos River and Kimmeria Torrent –two intermittent streams– in north-eastern Greece. The total sediment concentration was calculated, in both streams, by means of various nonlinear regression equations and by means of the formulas of Yang, after calibrating the coefficients of the formulas. In the computations according to the Yang formulas, two different states were examined regarding the incipient motion: one considering and one disregarding the critical conditions. The results obtained from Yang’s multiple regression-derived equations had a better fit compared to the original equations and were acceptable in both cases. Ultimately, two counterparts of Yang’s stream sediment transport formulas were constructed and made available to the readership. The comparison between the calculated and measured total sediment concentrations was achieved by means of several statistical criteria. The results indicate that the modified formulas of Yang can be successfully used for the determination of the total sediment concentration in Kosynthos River and Kimmeria Torrent.

Hybrid Fuzzy Multi-Criteria Analysis for Selecting Discrete Preferable Groundwater Recharge Sites

This study proposes a hybrid fuzzy multi-criteria methodology for the selection of the most preferable site for applying managed aquifer recharge (MAR) systems by utilizing floodwaters. The use of MAR can increase water resources for later water utilization in case of drought. In this multi-criteria problem, seven recharge sites are under consideration, based on nine criteria, aiming to make a final list of their relative ranking. A fuzzy analytic hierarchy process (FAHP) based on the logarithmic fuzzy preference programming (LFFP) method is used to determine the weights of criteria. LFFP is an optimization-based method that produces a priority vector from a fuzzy pairwise comparison matrix. Furthermore, fuzzy inference systems (FIS) based on the Mamdani approach are used to estimate the rating of each alternative with respect to the criterion examined, and then the final evaluation of the alternatives is obtained. A FIS is a fuzzy if–then rule-based system where the experts’ qualitative knowledge is translated into numerical reasoning for each individual criterion. The proposed methodology is applied in the aquifer system of the agricultural plain located to the southeast of the city of Xanthi in the Prefecture of Xanthi, NE Greece.

The vascular flora of damp meadows and mires in W Rhodopi (NE Greece)

The vascular flora of damp meadows and mires in W Rhodopi (NE Greece)

The role of Natura 2000 network in protecting the orchid flora of East Macedonia (NE Greece)

East Macedonia (northeast Greece) is a relatively small part of Greece, where a considerable number of orchid taxa occurs. Some of these orchids can only be found there and this fact makes the specific area of Greece unique. In this study, an up-to date database of orchid records was used to assess the effectiveness of the existing Natura 2000 network. Specifically, the effectiveness of the Natura 2000 network was evaluated by identifying the number of orchids whose distribution is overlapping to a lesser or greater extent with the network, which chorological categories are included/excluded from it, and whether the rare and threatened orchid taxa are adequately distributed within that. Out of the 73 orchid taxa recorded in East Macedonia so far, 14 taxa are exclusively distributed outside the Natura 2000 network. Specifically, the Natura 2000 network is not overlapped with a number of Balkan and Mediterranean orchid taxa, which are only sparsely found in East Macedonia. Moreover, most of the orchid taxa that have been classified in the threat categories of the IUCN are distributed within the Natura 2000 network of East Macedonia, and specifically, some of the most threatened ones are almost exclusively distributed within that network. Consequently, although the Natura 2000 network is not congruent with the distribution of a number of species of southern origin, which are widely distributed elsewhere in Greece, it can conserve important floristic elements of Greece, which are orchid taxa of northern or central European origin.

Impact of River Damming on Downstream Hydrology and Hydrochemistry: The Case of Lower Nestos River Catchment (NE. Greece)

In this paper, a series of field surveys were carried out along the Nestos River watershed (NE Greece) to assess the influence of two hydropower dams (Thissavros and Platanovrisi) upon the hydrology, hydrochemistry and nutrients stoichiometry of the river. Results showed that Nestos hydrology, downstream of the reservoirs, is entirely governed by the man-induced hydropower-driven dam retention/release policy. Dams’ operation increased the retention of dissolved inorganic nitrogen (DIN) and total suspended solids (TSS) significantly, affecting their downstream fluxes, even under water release regime. On the contrary, dams’ construction and operation did not seem to influence the downstream fluxes of dissolved inorganic phosphorus (DIP) and silica (DSi), although these elements also depended on the releasing policy. DIN retention, combined with the dependence of DIP to the water level of Thissavros, resulted in alteration of the N:P ratio at the downstream part. Almost all nutrients were stored at the bottom layer of Thissavros reservoir, especially under the summer stratification regime. Platanovrisi reservoir acts as a buffer zone between Thissavros and the Nestos downstream part. Anoxic conditions in the reservoirs favour the transformation of nitrates into ammonia and the remineralization of phosphorus from sediments, creating a degraded environment for freshwater fauna.