Lake Volvi Research Articles

Assessment of Environmentally Minimum Water Level in a Mediterranean Lake Using Morphological, Hydrological and Biological Factors

Water resources management requires comprehensive and integrated approaches that jointly consider hydrological, ecological and social factors. The assessment of lakes’ environmentally minimum water level is a critical tool for the sustainable management and protection of their ecosystems. This work combines the morphological, hydrological and biological factors of a Mediterranean lake (Lake Volvi, northern Greece) to assess its environmentally minimum water level. Initially, the morphological characteristics of the lake’s bottom were analyzed, with consideration given to the protection of the lake’s ecosystem and to the need to meet the water requirements for economic activities. Then, a hydromorphological analysis was conducted, relying on the surface water inflows to the lake from its hydrological catchment and the lake’s water level -volume relationship. In addition, the water level requirements of the biological communities of macrophytes, benthic macroinvertebrates, and fish, as revealed after samplings were taken from the lake’s littoral zone, are considered. Based on the above methodologies, the environmentally minimum water level of Lake Volvi is proposed to be lowered by as much as 35.8 m from February to May and 35.3 m from June to January in order to maintain the ecological integrity of the lake and the sustainable use of its water resources. The present study establishes a foundation for informed water resource management; however, ongoing research can improve methodologies and address emerging questions, fostering advancements in sustainable water management practices.

Energy Budget, Water Quality Parameters and Primary Production Modeling in Lake Volvi in Northern Greece

A lake’s water quality and its ecosystem structure are mainly determined by heat storage change through its energy budget, dissolved oxygen, nutrients and primary productivity. A one-dimensional water quality model for lakes was used to estimate temperature, dissolved oxygen, phytoplankton (as chlorophyll-α), and inorganic and organic phosphorus. Evaporation, energy budget and surface water temperature were also computed. The results of the mathematical model simulation are presented and evaluated. Data from Lake Volvi in Central Macedonia (in northern Greece) for three successive years (2013 to 2015) were used to calibrate and recalibrate the model. The model results of water temperature, dissolved oxygen and primary productivity (Chlα) were compared with measurements for the years 2013 to 2015. The comparison showed that the predicted values of these parameters were all in good agreement with the measurements. The simulation results of water quality parameters generally exhibited the same seasonal dynamic and inter-annual variations as the measured data. The simulation results of the model application provided important information on changes in the physical, chemical and biological variables of the lake. The water temperature and heat fluxes at the water–atmosphere interface are crucial variables related to climate changes.

Status and Population Trends of Great Cormorant Phalacrocorax carbo sinensis Breeding in Greece

We analysed trends in the breeding population of Great Cormorants in Greece during the period 1988–2014 when at least 20 colonies were recorded. The number of colonies doubled over the study period reaching 14 in 2014 from seven in 1988. There was also a continuous increase in the number of nests: from 952 in 1988 to 9256 in 2014, presenting an annual change of +26.5% ± 0.05 (SD). Most of the colonies were situated in freshwater lakes, three in deltas and one on the seacoast. Nine colonies were mixed with other colonially nesting species (mostly from the Ardeidae family). Of the 14 colonies 11 were found in trees. Two colonies were situated on the ground, four in bushes, two on reed rhizome islets and one on cliff ledges. Five out of the 14 active colonies in 2014, comprising 87% of the total recorded nests, were in wetlands of low altitude (0–45 m a.s.l.). The rest were situated in mountainous wetlands at altitudes ranging from 235 to 853 m a.s.l. One colony, at Lake Kerkini, contained the majority of nests in Greece (6650, being 72% in 2014). The second largest colony, at Lake Volvi, had 900 nests, followed by the Greek part of Prespa with 625 nests (in three colonies) in 2014. The percentage of nests in newly established colonies increased after 2003, reaching its highest value (14%) in 2009. The reason for the growth in both colonies and nests over the years is attributed to the increasing availability of fish, the protection status of wetlands and the absence of disturbance. Particularly after 2002 the species increased in numbers and established colonies in new areas, which is probably related to the expanding breeding populations of the species in north-eastern European countries and a corresponding increase in wintering numbers in Greece. This needs further attention by monitoring and research.

Age, Growth, Reproduction and Fecundity of Roach Rutilus rutilus from Volvi Lake, Northern Greece

The roach, Rutilus rutilus, is a Cyprinid which is widely distributed throughout freshwater systems in Europe. It is one of the most abundant and important commercial fish species in Greece. Age, growth, reproduction and fecundity of roach were studied in Lake Volvi from 1997-1998 females had higher growth in length (L∞=277.18 mm, k=0.097) than adult males (L∞=185.60 mm, k=0.148). All males older than one year and larger than 70 mm, and all females older than two years and larger than 80 mm were sexually mature. The breeding period spanned from the end of March till mid April. Fecundity ranged from 2,036 to 31,653 eggs (mean 8,102 eggs) and relative fecundity from 76.06 to 333.94 eggs/g (mean 186.78 eggs/g). Diameter of eggs were 1.3 ± 0.07 mm and weighted 0.0011 ± 0.0002 g . The weight of eggs were independent of length and age of individuals (P>0.05), however, there was a significant relationship between weight and egg diameter (P<0.05). Absolute fecundity depended on length, weight and age of the females. The relationship between absolute fecundity and length were less obvious in the case of relative fecundity and egg size. Estimated growth was at the lower end when compared with other studies conducted elsewhere.

Integrated Water Management Approach for Adaptation to Climate Change in Highly Water Stressed Basins

Adaptation aims at increasing the resilience of natural and human systems to current and future impacts of climate change. The main objective of the current research is to introduce an innovative methodological framework which can effectively assess adaptation measures in basins with severe water deficits by coupling hydrology, climate change and management scenarios, leading to accurate decision making. In this paper, both supply and demand adaptation measures were proposed in line with various regional, national and European policies in order to improve the severe water problem of the Mygdonia basin. The overexploitation of the surface water systems (Lakes Koronia and Volvi) and groundwater resources of the Mygdonia basin during the previous decades, along with the projected decrease of the future water availability, due to climate change, accentuate the need for concerted action towards adaption to climate change. The measures include the increase of a stream diversion towards Lake Koronia, the increase of the embankment elevation at the outfall point of Lake Volvi, the restructuring of crops and their combinations. The measures were examined in terms of their sustainability and effectiveness in the short-term (2020–2050) and long-term (2050–2080) future periods under the most reliable climatic model. The results indicate that the application of demand management measures is more efficient compared to supply oriented solutions for addressing the future water deficit of the Mygdonia water system. The combination of crop restructuring and the decrease of agricultural land proved to be the most efficient and sustainable solution.

Concentration, fractionation, and ecological risk assessment of heavy metals and phosphorus in surface sediments from lakes in N. Greece.

The presence of phosphorus (P) and heavy metals (HMs) in surface sediments originating from lakes Volvi, Kerkini, and Doirani (N. Greece), as well as their fractionation patterns, wereinvestigated. No statistically significant differences in total P content were observed among the studied lakes, but notable differences were observed among sampling periods. HM contents in all lakes presented a consistent trend, i.e., Mn > Cr > Zn > Pb > Ni > Cu > Cd, while the highest concentrations were recorded in Lake Kerkini. Most of the HMs exceeded probable effect level value indicating a probable biological effect, while Ni in many cases even exceeded threshold effects level, suggesting severe toxic effects. P was dominantly bound to metal oxides, while a significant shift toward the labile fractions was observed during the spring period. The sum of potentially bioavailable HM fractions followed a downward trend of Mn > Cr > Pb > Zn > Cu > Ni > Cd for most lakes. The geoaccumulation index Igeo values of Cr, Cu, Mn, Ni, and Zn in all lakes characterized the sediments as "unpolluted," while many sediments in lakes Volvi and Kerkini were characterized as "moderately to heavily polluted" with regard to Cd. The descending order of potential ecological risk [Formula: see text] was Cd > Pb > Cu > Ni > Cr > Zn > Mn for all the studied lakes. Ni and Cr presented the highest toxic risk index values in all lake sediments. Finally, the role of mineralogical divergences among lake sediments on the contamination degree was signified.

Length-Weight relations and condition factor of roach Rutilus rutilus (Linnaeus, 1758) in Lake Volvi (Northern Greece)

Length-weight relations (LWRs) and different indices of condition factor for roach from Lake Volvi (Northern Greece) were estimated. Results showed that roach are heavier of a given length in Lake Volvi than in other areas worldwide, with females exhibited higher weight than males of the same length. Significant differences (P<0.05) of LWRs were also exhibited between sexes depending on month. CLARK condition factor peaked at the end of summer displaying no significant difference between sexes, whereas the other three estimated condition factors (Allometric, FULTON, LE CREN) peaked in winter. The estimation of different proxies of condition factor disaggregated by sex might reduce the uncertainty raised by the estimation of fish growth.

Biochemical and molecular responses of cyprinids in two Mediterranean lacustrine ecosystems: Opportunities for ecological assessment and biomonitoring

Lacustrine ecosystems have been altered by accelerating pollution, excessive nutrient and organic load, water abstraction, and are susceptible to climate change. Hence, suggesting sensitive and reliable biomarkers for early assessments of their status is of urgent need. In this study, two freshwater commercial fish species, Cyprinus carpio (carp) and Carassius gibelio (prussian carp) from two lakes (i.e. Koronia and Volvi, Northern Greece) with different anthropogenic pressures were used and a battery of biochemical and molecular biomarkers related to stress response were analyzed in fish gills and liver. In parallel, water physicochemical parameters (T, DO, pH, conductivity, salinity), BOD5 and nutrient (N-NO3, N-NO2, N-NH4, P-PO4) concentrations were measured. Results showed that Lake Koronia had higher conductivity and salinity values and N-NO2 concentrations. Levels of Heat Shock Response (HSR), MAPK phosphorylation, protein carbonylation, lipid peroxidation products, Bax/Bcl-2 ratio, ubiquitination and caspases were increased in gills and liver of both fish species sampled from Lake Koronia in relation to those of Lake Volvi. Likewise, liver lipid content was increased in both fish species sampled from Lake Koronia compared to those sampled from Lake Volvi. The results indicate and reflect the higher environmental degradation that prevails in Lake Koronia ecosystem in comparison to that of Lake Volvi. The fish species studied showed different susceptibility depending on the biomarkers examined. In addition, our results from both examined species provide insight into the mechanisms involved in acclimatization to stressful environments and support the role of the studied biomarkers as sensitive and reliable tools for ecological assessments of lake ecosystems in biomonitoring studies.

Karyotype and chromosomal characteristics of rDNA of Cobitisstrumicae Karaman, 1955 (Teleostei, Cobitidae) from Lake Volvi, Greece.

The karyotype of Greek cobitid fish Cobitisstrumicae Karaman, 1955, from Lake Volvi, Greece, a representative of one of its two major intraspecific phylogenetic lineages, was analysed by means of sequential Giemsa-staining, C-banding, silver-staining, CMA3 fluorescence banding and also by in situ hybridization (FISH) with rDNA probe. The diploid chromosome number was 2n = 50, karyotype composed of 10 pairs of metacentric to submetacentric and 15 pairs of subtelocentric to acrocentric chromosomes. The nucleolus organizer regions (NORs) as revealed by Ag- and CMA3 staining and FISH were situated in the telomeric region of the fourth submetacentric chromosome pair. The chromosomes contained very low content of C-positive heterochromatin. No heteromorphic sex chromosomes were detected. This first karyotype report for any species of lineage Bicanestrinia Băcescu, 1962 shows a simple karyotype dominated by acrocentric chromosomes and possessing single NOR-bearing chromosome pair. Cytotaxonomic implications of this finding for the taxonomy of the genus Cobitis Linnaeus, 1758 are further discussed.

Food web modelling on the structure and functioning of a Mediterranean lentic system

Τhe ecosystem structure of a Mediterranean lentic system (Lake Volvi, Northern Greece) was assessed and quantified for the first time, using the Ecopath with Ecosim model. Biological and fisheries-related data were collected during 2014–2015 from field surveys; moreover, operational and other data concerning fisheries exploitation were assessed by interviews. The model will (a) describe the ecological structure of the lake in terms of trophic flows (b) disaggregate the impacts imposed by fishing and other factors on the food web and (c) investigate the ecosystem’s functional changes by testing the introduction of a new fish species. Lake Volvi constitutes a mature system whose food web is characterized by “bottom-up” processes, exhibiting a “good” systemic resistance to unexpected perturbations and a rather low intensity of fisheries exploitation. Simulations from 2015 to 2025 revealed that an increase in fishing effort and/or stocking with the new species will have negligible impact on the food web and will not affect negatively the fisheries resources and top megafauna. The model presented provides key ecosystem information that is lacking for most European freshwaters systems, which can be useful in assessing their ecosystem structure and in simulating the pressure of fisheries exploitation on their food web.

Multi-dimensional Interpretation of Radiomagnetotelluric and Transient Electromagnetic Data to Study Active Faults in the Mygdonian Basin, Northern Greece

The Mygdonian Basin is located about 45 km NE of the city center of Thessaloniki in northern Greece. We conducted an electromagnetic (EM) survey that covers parts of the epicenter area between Lake Volvi and Lake Langada of the local 1978 earthquake that caused structural damage in the city center of Thessaloniki. Ambient noise measurements in the basin strongly suggest a complex 3-D tectonic setting. Hence, near-surface electromagnetic measurements were carried out to map the local fault pattern in the research area. We conducted radiomagnetotelluric (RMT) and transient electromagnetic (TEM) measurements along eight profiles, giving a total number of 443 RMT and 107 TEM soundings to study the spatial electrical conductivity distribution. In this context, RMT data are used to study the shallow conductivity structure down to about 35 m, whereas the TEM data explore the conductivity distribution down to a depth of 200 m. The 1-D and 2-D interpretation of RMT and TEM data indicate a local fault pattern in the survey area that was also studied by 3-D modeling of the RMT data.

A revision of the Rutilus complex from Mediterranean Europe with description of a new genus, Sarmarutilus, and a new species, Rutilus stoumboudae (Teleostei: Cyprinidae).

By combining morphology, ecology, biology, and biogeography with the available molecular (sequence variation of the entire mitochondrial cytochrome b gene; cyt-b) and karyology data, the taxonomy of several species of the Rutilus complex inhabiting southern Europe is revised. Rutilus stoumboudae, new species, is described from Lake Volvi, Greece. It differs from Rutilus rutilus in possessing more total GR and less branched rays in both dorsal and anal fins and in its placement in the cyt-b based phylogeny of the genus. The resurrected genus Leucos Heckel, 1843 (type species Leucos aula, Bonaparte, 1841), which according to molecular data diverged from Rutilus more than 5 million years ago, during the Messinian salinity crisis, includes five species of small size, without spinous tubercles on scales and head in reproductive males, pharyngeal teeth formula 5-5, and all show a preference for still waters. Leucos aula is the Italian species endemic in the Padany-Venetian district: L. basak is widespread in Croatia, Albania, Montenegro and former Yugoslav Republic of Macedonia (FYROM); L. albus, recently described from Lake Skadar, Montenegro, is also found in rivers Moraca and Zeta (Montenegro). L. albus differs from L. basak, its closest relative, in having more scales on the LL and less anal-fin rays; L. panosi is endemic to the western-Greece district, and L. ylikiensis is endemic to lakes Yliki and Paralimni in eastern Greece (introduced in Lake Volvi). Among the nominal species examined, Rutilus karamani, R. ohridanus, R. prespensis and R. prespensis vukovici are all junior synonyms of Leucos basak. Rutilus vegariticus is definitively regarded as junior synonym for R. rutilus. Sarmarutilus n.gen. is a monotypic genus, with Sarmarutilus rubilio as the type species. According to phylogenetic data, Sarmarutilus rubilio is basal to a cluster of species that includes Leucos basak, L. albus, L. aula, L. panosi and L. ylikiensis. Sarmarutilus possibly evolved in pre-Messinian time, in the Lago Mare, entered the Mediterranean area during the Messinian Lago Mare phase of the Mediterranean Sea and survived only in the Tuscany- Latium district. This genus differs from Leucos in having large pearl organs on the central part of head and body scales in mature males and for the habitat preference, being a riverine-adapted species. It differs from Rutilus in pharyngeal teeth formula (5-5 in Sarmarutilus and 6-5 in Rutilus), size (small in Sarmarutilus and large in Rutilus) and for the preferential habitat (riverine vs. still water). Finally, lectotypes for Leucos basak, Leucos aula, and Sarmarutilus rubilio are designated.

New Fisheries-related data from the Mediterranean Sea (April 2014)

As part of its policy, Mediterranean Marine Science started from 2014 to publish a new series of collective article with fisheries-related data from the Mediterranean Sea. In this first collective article we present length frequencies and weight-length relationships for the northern brown shrimp Farfantepenaeus aztecus in the eastern Mediterranean, length-weight relationships for 10 fish species in the North Aegean Sea, the feeding habits for 11 sparid fishes in the North Aegean Sea, a review of the existing literature on the feeding and reproduction of common carp Cyprinus carpio in Anatolia (Turkey) and mouth dimensions and the relationships between mouth area and length for seven freshwater fishes from Lake Volvi (Northern Greece).

Part I: Temporal and spatial distribution of multiclass pesticide residues in lake waters of Northern Greece: application of an optimized SPE-UPLC-MS/MS pretreatment and analytical method

The present work describes the application of an analytical procedure, utilizing ultra performance liquid chromatography (UPLC) coupled with mass spectrometry instrumentation, for the determination of 253 multiclass pesticides, classified in six different groups. Solid phase extraction was applied for the isolation and pre-concentration of target compounds in water samples. Surface waters of the lakes located in Northern Greece (Volvi, Doirani, and Kerkini), were collected in two time periods (fall/winter 2010 and spring/summer 2011) and analyzed, applying the developed analytical methods. Spatial distribution of detected pesticides was visualized using interpolation methods and geographical information systems (GIS). Pesticides with maximum concentrations were amitrole, propoxur, simazine, chlorpyrifos, carbendazim, triazophos, disulfoton-sulfone, pyridaben, sebuthylazine, terbuthylazine, atrazine, atrazine-desethyl, bensulfuron-methyl, metobromuron, metribuzin, rotenone, pyriproxyfen, and rimsulfuron. In Lake Kerkini, mainly carbamates and triazines were determined at elevated concentrations, near the coastal point of the NW side of the lake. Seasonal variations were strong among the applied pesticide classes and determined concentrations, indicating the contribution of pesticide application patterns and rainfall. Lake Doirani exhibited organophosphate pesticides at higher concentrations mainly at coastal points, while triazines emerged as the main pollutant during spring sampling. Lake Volvi exhibited the highest pesticide concentrations, mostly triazines and ureas at the central part of the lake. The occurrence of extreme values and nonconstant seasonal variations indicated that the concentrations were increased disproportionately during the second sampling, as a result of the varying contribution of pollution sources right after the application period. In all cases, the total concentration of pesticides increased during the second sampling period.

Part II: temporal and spatial distribution of multiclass pesticide residues in lake sediments of northern Greece: application of an optimized MAE-LC-MS/MS pretreatment and analytical method

The development and application of an analytical methodology for the pretreatment and determination of 253 multiclass pesticides, in lake sediment samples, using liquid chromatography coupled with mass spectrometry (LC-MS/MS) are described in this work. Sediments of lakes Volvi, Doirani, and Kerkini, located in northern Greece, were collected in two-time periods (fall/winter 2010 and spring/summer 2011) and analyzed, applying the developed analytical methodology. Microwave-assisted extraction (MAE) was applied to extract the pesticide residues from lake sediment samples. Analytical results were stored, categorized, and visualized using geographical information systems, in order to assess and observe spatial and temporal variations of the pollution. Main pesticides that were detected included the following: amitrole, tebuconazole, phoxim, diniconazole, sethoxydim, temephos, tetrachlorvinphos, pendimethalin, boscalid, disulfoton sulfone, lenacil, propiconazole, cycloxydim, pyridaben, and terbuthylazine. Amitrole, diniconazole, and tebuconazole were found to be common in all three lakes. Lakes Kerkini and Doirani exhibited increased concentrations during the first sampling period (winter 2010) with predominant pesticide classes, triazines/triazoles and organophosphates. Pollution is mainly located near the populated villages of the lakes and the nearby cultivations. During the second sampling period, pesticide concentrations appear lower and located in sediments near the center of the lake. Lake Volvi exhibits increased pesticide concentrations during the second sampling period, temporal and spatial variations and different pesticide profile pattern. Increased pollution occurs near the center of the lake during the first sampling period, mainly comprised by triazines/triazoles and organophosphates. During the second sampling period, the majority of the sediment samples demonstrated a different pesticide profile dominated by unclassified pesticides and triazines/triazoles. Mineralogical analysis of the samples demonstrates that sediments are mainly composed of clay, mud, and sand particles, and they present spatial variations. Near the center of the lakes, sediments appear to be more fine-grained with higher clay content and are more likely to adsorb pesticides.

Water resources management in the watershed of Volvi Lake

The decrease of available water resources, the water quality degradation as well as the rapid increase of population combined with the growth of human activities, impose today the development of a science that concerns the Management of Water Resources. Lake Volvi faces a lot of problems, the most important being the water level drop, which is mostly due to the big quantities of water flowing through to Rihios River and to the wrong management of irrigation water. The study area of the present research consists of the watershed of Lake Volvi, situated in Northern Greece, 39 km away from the city of Thessaloniki. The objective of this study is the estimation of the water balance of the hydrologic basin of Lake Volvi with a Corporate Management program, using Visual Fortran and the creation of scenarios for better management of the water resources of the region. Lake Volvi is situated next to Lake Koronia, both of them belonging to a wider region that forms the geological basin of Mygdonia. Lake Volvi is the recipient of the water draining from Lake Koronia. The water that drains from Lake Volvi is discharged into the gulf of Strymonikos through Rihios River. Firstly, a close analysis is attempted for the estimation of the water balance of the entire hydrologic basin of Lake Volvi with the method of Turc, which is used widely throughout the world. Next, in order to simulate the lake, an administrative model is used, written in Visual Fortran. A rational management of the hydrological elements of the region is attempted with the creation of four alternative scenarios. After the execution of the Corporate Management program, the results show that the main problem for Lake Volvi is the water leaking to Rihios River. Moreover, the research also shows that it is important to reduce the water used for irrigation. As a final result, it is an imperative need to develop water resources management plans for the restoration of the entire region.

The threat of alluviation of lakes resulting from torrents (case study: lake volvi, north greece)

Lakes or natural reservoirs are usually formed by the water supplied by torrents runoff. Furthermore, runoff, according to the torrential environment that forms the watershed (climate, geology, vegetation and relief) is usually associated with debris fl ow. As a result, many lakes and reservoirs are undergoing an alluviation process which leads to an important reduction of their total capacity. In fact, long-term process of torrents may threaten their existence. Lakes and reservoirs have an important role since the impounding water is used for multi purposes such as municipal supply, irrigation and recreation. Often, lakes form wetlands that are really important and are protected by national or international treaties. In this paper, the methodology we use involve the analysis of torrential environment (potential) of the lake Volvi watershed. Moreover, the mean annual sediment yield calculated according to Gavrilovic method so as to assess the risk of alluviation. Also, Kronfellner‐Kraus method used in order to take under consideration the sediment that can fl ow into the lake after an extraordinary fl ood event. Finally, fl ood control works proposed so as minimize the threat of alluviation. The present study shows that the torrential environment (potential) is rather moderate, although during intense rainfalls great volume of water and

Genetic monitoring and effects of stocking practices on small Cyprinus carpio populations

The ability to detect genetic differences both in space and time is crucial for conserving genetic variation. It can reveal genetic diversity and genetic composition changes of declining native populations that are supported through stocking with captive bred individuals. The present study was designed to analyse the temporal stability of a declining common carp (Cyprinus carpio) population from Lake Volvi (North Greece). Polymorphism was evaluated using seven microsatellite loci at two sampling time points (separated by 12 years). The genetic variability of four additional populations (from two rivers and two lakes) in Northern Greece was also investigated for comparison. Heterozygosity values (0.692–0.868) and allelic richness (8.530–11.148) were high for all studied populations and comparable to other European populations. However, the analysis of temporal common carp samples from Lake Volvi revealed a significant change in their genetic composition and admixture analysis demonstrated significant introgression of stocked individuals into the native population. Both temporal and point estimate methods revealed low effective size (Ne = 61–171.3) for this population, possibly a result of an ancient genetic bottleneck that led to population decline and/or recent anthropogenic interventions. This low Ne has rendered the native population vulnerable to alteration of its genetic composition. Our study demonstrates that enhancement programs should be applied cautiously, especially for small populations. Moreover, it underlines the need for temporal analyses, which may contribute to the evaluation of previous management policies and to future decision making.

Genetic characterization of common carp (Cyprinus carpio) populations from Greece using mitochondrial DNA sequences

Wild common carp from two lakes and two rivers in Greece were genetically characterized with sequencing analysis of two mitochondrial DNA segments: cytochrome b (1119 bp) and D-loop (646 bp). A total of 9 variable singleton sites and 7 unique haplotypes were detected. A common haplotype was found in three out of the four populations examined, which seems to be the ancestral one and represents the European origin of common carp from Greece. This haplotype could be also justified by the introductions reported with individuals belonging to the Central European race, into many natural habitats in Greece. Limited genetic variation — in Evros and Aliakmonas populations — could be due to bottleneck effects and small effective population sizes, whereas the different haplotypes found in Lake Volvi could represent different common carp stocks. Values of sequence divergence among Greek haplotypes ranged from 0.0006 to 0.0023. The Neighbour-Joining (NJ) phylogenetic tree constructed based on the combined sequences, reveals that the populations of common carp from Greece belong to the European group of populations — which is highly divergent from the South East-Asia cluster — and to the subspecies Cyprinus carpio carpio.

Assessment of the Quality Characteristics of Two Lakes (Koronia and Volvi) of N. Greece

Quality parameters from 17 sampling stations from Lake Koronia and 18 from Lake Volvi were determined during sampling period of one year. Physicochemical parameters (pH, conductivity, DO) did not show remarkable differences neither between sampling sites nor between sampling periods. Nutrient concentrations (nitrogen and phosphorus compounds) were higher in lake Koronia than in Volvi showing relatively small temporal and spatial variations. As far as heavy metals in sediments, lake Koronia is considerably more polluted than Volvi lake especially with the metals Fe, Mn, Zn, Pb and Cd. The mean total concentrations of metals in lake Koronia decrease in the order Mn > Zn > Cr > Pb > Cu > Fe > Cd. The mean total concentrations of metals in lake Volvi decrease in the order Mn > Zn > Cr > Cu > Pb > Fe > Cd.