Peer-reviewed publications in scientific journals for Lake Karla, Greece, its aquifer and watershed

Up to 2009

Ananiadis CI (1956) Limnological study of Lake Karla. Bull. Inst. Océanogr. 1083:1-19

Zalidis GC, Takavakoglou V, Panoras A, Bilas G, Katsavouni S (2004) Re-establishing a sustainable wetland at former Lake Karla, Greece, using Ramsar restoration guidelines. Environ. Managem. 34:875-886

ABSTRACT: Lake Karla, Greece, was almost completely drained in 1962 both to protect surrounding farmlands from flooding and to increase agricultural area. Loss of wetland functions and values resulted in environmental, social, and economic problems. A number of restoration plans were proposed to address these problems. The plan approved by the government in the early 1990s proposed construction of a 4200-ha reservoir solely to improve water storage and flood attenuation functions. However, the Ramsar Scientific and Technical Review Panel states that the primary goal of any restoration project is to create resilient and sustainable ecosystems, as measured on a human timescale, in order to improve the ecological character and enhance the socioeconomic role that the wetland plays in the watershed. This study utilizes Ramsar guidelines for sustainable restoration of Lake Karla. Eight additional restoration measures are proposed based on functional analysis of the wetland to enhance additional wetland functions and support multiple values for humans and nature.

Loukas A, Mylopoulos N, Vasiliades L (2007) A modeling system for the evaluation of water resources management strategies in Thessaly, Greece. Water Resour. Managem. 21:1673-1702

ABSTRACT: A modeling system was developed to evaluate the sustainability of water resources management strategies in the two major basins of Thessaly Region in Greece, namely the Pinios River and the Lake Karla basins. The intense and extensive agriculture of water demanding crops, such as cotton, and the absence of reasonable water resources management have lead to a remarkable water demand increase, which is usually fulfilled by the over-exploitation of groundwater resources. This unsustainable practice has deteriorated the already disturbed water balance and accelerated water resources degradation. The modeling system consists of a hydrological model, a reservoir operation model and methods for the estimation of water demands. The study area was sub-divided into sub-basins and water balance analyses were performed for each sub-basin and each control node of the system for a number of water resources management strategies. Four strategies of hydro-technical project development were coupled with two strategies of groundwater withdrawal and three water demand strategies. In total, more than 24 water management strategies were evaluated. The results showed that, under the existing water resources management, the water deficit of the Pinios River and Lake Karla basins is very large. However, the development of proposed hydro-technical projects in the Pinios River basin coupled with water demand management measures, like improvement of existing water distribution systems, change of irrigation methods, and changes of crop cultivation could alleviate the problem and lead to sustainable and ecological use of water resources in the study area.

Laspidou C, Vaina V (2009) Ecosystem modeling of sediment dynamics in the constructed wetland Carla in Central Greece. Int. J. Design Nature Ecodyn. 3:273-280

ABSTRACT: Constructed wetlands are complex dynamic ecosystems. Ecosystem-level modeling of the processes that take place in a constructed wetland is a useful tool for understanding wetland function and structure and for making predictions. We present a primary productivity model for the wetland that is currently under construction in the area of Carla in central Greece, restoring one of the most important wetlands in Europe that was drained in 1962. The model includes the area’s hydrology and geomorphology and is used to explore the role of different wetland structures and functions on the dynamics of primary producers and sediments in the constructed ecosystem, in order to provide a better understanding of the processes involved and the nutrient dynamics in these processes.

Vasiliades L, Loukas A, Patsonas G (2009) Evaluation of a statistical downscaling procedure for the estimation of climate change impacts on droughts. Nat. Haz. Earth System Sci. 9:879-894

ABSTRACT: Despite uncertainties in future climates, there is considerable evidence that there will be substantial impacts on the environment and human interests. Climate change will affect the hydrology of a region through changes in the timing, amount, and form of precipitation, evaporation and transpiration rates, and soil moisture, which in turn affect also the drought characteristics in a region. Droughts are long-term phenomena affecting large regions causing significant damages both in human lives and economic losses. The most widely used approach in regional climate impact studies is to combine the output of the General Circulation Models (GCMs) with an impact model. The outputs of Global Circulation Model CGCMa2 were applied for two socioeconomic scenarios, namely, SRES A2 and SRES B2 for the assessment of climate change impact on droughts. In this study, a statistical downscaling method has been applied for monthly precipitation. The methodology is based on multiple regression of GCM predictant variables with observed precipitation developed in an earlier paper (Loukas et al., 2008) and the application of a stochastic timeseries model for precipitation residuals simulation (white noise). The methodology was developed for historical period (1960–1990) and validated against observed monthly precipitation for period 1990–2002 in Lake Karla watershed, Thessaly, Greece. The validation indicated the accuracy of the methodology and the uncertainties propagated by the downscaling procedure in the estimation of a meteorological drought index the Standardized Precipitation Index (SPI) at multiple timescales. Subsequently, monthly precipitation and SPI were estimated for two future periods 2020–2050 and 2070–2100. The results of the present study indicate the accuracy, reliability and uncertainty of the statistical downscaling method for the assessment of climate change on hydrological, agricultural and water resources droughts. Results show that climate change will have a major impact on droughts but the uncertainty introduced is quite large and is increasing as SPI timescale increases. Larger timescales of SPI, which, are used to monitor hydrological and water resources droughts, are more sensitive to climate change than smaller timescales, which, are used to monitor meteorological and agricultural droughts. Future drought predictions should be handled with caution and their uncertainty should always be evaluated as results demonstrate.

2010 - 2014

Chatzinikolaou Y, Ioannou A, Lazaridou M (2010) Intra-basin spatial approach on pollution loadestimation in a large Mediterranean river. Desalination 250:118-129

ABSTRACT: In order to find the segments of Pinios River which lack the retention capacity of the BOD and nutrient input, the difference of the estimated input and output pollution loads was compared at upstream and downstream clustered areas of a total of 73 segments. Catchment areas ranged from 1 to 11,300 km2. Emissions were always higher than the actual transport, therefore retention was assumed to take place. Specific runoff, percentage of the surface water area and the calculated input of pollution loads (BOD, P, N) varied between the different Pinios River basin catchment areas. The transport to the emission load ratio was different between large and small catchments. The rate of retention among consecutive segments revealed that four lowland segments lacked in their relative retention capacity.

Laspidou C, Kakoulidis I, Loukas A (2011) Ecosystem simulation modeling of nitrogen dynamics in the restored lake Karla in Greece. Desal. Water Treat. 33:61-67

ABSTRACT: Restored lakes are complex dynamic ecosystems. Ecosystem-level modeling of the processes that take place in a lake is a useful tool for understanding lake function and structure and for making predictions. A nitrogen dynamics model for the lake currently undergoing restoration in the area of Karla in Greece is presented. The model includes the area’s hydrology and geomorphology and is used to explore the role of different lake structures and functions on nitrogen dynamics in the restored ecosystem, in order to provide a better understanding of the processes involved in nutrient retention by the lake. Seven forms of nitrogen are included in the model: ammonium, nitrite/nitrate, organic, nitrogen stored in algae and macrophytes, and nitrogen stored in active and deep sediments. The processes of ammonification, remineralization, nitrification, denitrification and sedimentation are mathematically modeled using equations from the literature adjusted to the hydrology and special conditions of lake Karla. Results show that most of the incoming nitrogen is sequestered by the lake, while 6.7% of it gets lost in the atmosphere through denitrification. Primary producers play an important role in nitrogen cycling in the lake, while an important part of the nutrient is stored away permanently in deep sediments.

Oikonomou A, Katsiapi M, Karayanni H, Moustaka-Gouni M, Kormas KA (2012) Plankton microorganisms coinciding with two consecutive mass fishkills in a newly reconstructed lake. Scient. World J. Article no 504135

ABSTRACT: Lake Karla, Greece, was dried up in 1962 and its refilling started in 2009. We examined the Cyanobacteria and unicellular eukaryotes found during two fish kill incidents, in March and April 2010, in order to detect possible causative agents. Both microscopic and molecular (16S/18S rRNA gene diversity) identification were applied. Potentially toxic Cyanobacteria included representatives of the Planktothrix and Anabaenagroups. Known toxic eukaryotes or parasites related to fish kill events were Prymnesium parvum and Pfiesteria cf. piscicida, the latter being reported in an inland lake for the second time. Other potentially harmful microorganisms, for fish and other aquatic life, included representatives of Fungi, Mesomycetozoa, Alveolata, and Heterokontophyta (stramenopiles). In addition, Euglenophyta, Chlorophyta, and diatoms were represented by species indicative of hypertrophic conditions. The pioneers of L. Karla's plankton during the first months of its water refilling process included species that could cause the two observed fish kill events.

Sidiropoulos P, Papadimiitriou T, Stabouli Z, Loukas A, Mylopoulos N,Kagalou I (2012) Past, present and future concepts for conservation of the re-constructed Lake Karla (Thessaly-Greece). Fresen. Environ. Bullet. 21(10 A):3027-3034

ABSTRACT: Lake Karla (the ancient Lake Voiviis) occupied the lower depression plain of Thessaly region and was one of the most important wetlands in Greece until the 60's. The lake was completely drained in 1962, through a tunnel to Pagasitikos Gulf and has experienced a number of anthropogenic impacts including wetland loss, significant draw-down of the aquifer's water table leading to soil salinization, loss of ecological and aesthetic value. Restoration efforts started in the 80's, addressing to the re-establishment of a new functional reservoir and wetland. At the present time, the reservoir of the lake is almost refilled while the restoration project of the wetland is still ongoing. This study highlights the limnological history of Lake Karla along with its present ecological profile. Since the conservation of Mediterranean freshwater ecosystems requires new water management approaches considering both societal and ecosystemic needs in an integrated fashion, a critical review concerning the Karla's restoration project is discussed. Through Karla's example, as a Mediterranean climate basin, an integrated environmental approach is presented here which could also meet agricultural water demands.

Mitsoura M, Papaioannou N, Berillis P, Mente E, Kagalou I, Papadimitriou T (2013) The presence of microcystins in fish Cyprinus carpio tissues: an histopathological study. Int. Aquat. Res. 5,8

ABSTRACT: The occurrence of heavy cyanobacterial blooms has become a worldwide problem, as a consequence of eutrophication of the aquatic ecosystems; furthermore, 60% to 75% of these blooms have been found to be toxic. Microcystins (MCYSTs), the predominant toxins of cyanobacterial blooms, are associated with mortality and illness in both animals and humans. Laboratory-controlled experiments studying the effects of different microcystins on the common carp (Cyprinus carpio) have revealed various histopathological alterations. The aim of the present study is to investigate the effect of chronic or subchronic exposure of fish to microcystins under natural environmental conditions by examining the possible histopathological changes associated with a dense cyanobacterial bloom and determining the microcystin contents of fish tissues. Common carps (Ccarpio) were caught from Lake Karla (Greece), during a dense cyanobacterial bloom. The concentration of MCYSTs in the fish liver, kidney and muscle tissues was measured by enzyme-linked immunosorbent assay. The pseudogaster contents were analysed, and a histopathological examination was performed using light and electron microscopy. Severe alterations were detected in the liver and the kidney, suggesting that the toxic effects were caused by various pollutants that were particularly associated with microcystins. The histopathological findings are also discussed, taking into consideration the health conditions of the common carp as a commercial fish species. The mechanisms of expansion of the microcystins and the poisoning of aquatic organisms (e.g. fish) are not yet known in the Lake Karla ecosystem. Future research may focus on identifying the changes caused by microcystins and other factors that exert similar effects on fish tissues, as well as on establishing the overall combined effect of all these factors on fish health.

Nikouli E, Kormas KA, Berillis P,Karayanni H, Moustaka-Gouni M (2013) Harmful and parasitic unicellular eukaryotes persist in a shallow lake under reconstruction (L. Karla, Greece).Hydrobiologia 718:73-83

ABSTRACT: The reconstructed Lake Karla, Greece, has been undergoing its water-filling period since November 2009. In this paper, we aimed at investigating whether the unicellular eukaryotes, including the toxic/parasitic ones, that have been found during mass fish kills in the lake (March–April 2010), persist during the first warm period of the lake (May, August, November 2010). Given that microscopic characterization of some of these eukaryotes is not adequate for their identification, we analysed the 18S rRNA gene diversity of plankton samples. All the found phylotypes belonged to the phyla of Mesomycetazoa, Chlorophyta, Fungi, Alveolata, Cercozoa, Cryptophyta and Stramenopiles. Some members of these groups seem to persist in Lake Karla as they have been found in early spring as well. These microscopic eukaryotes are either ichthyotoxic/parasitic (e.g. Pfiesteria sp./Pseudopfiesteria shumwayae, some Fungi, Mesomycetazoa, Lagenidium sp., Cercozoa) or indicative of hyper-eutrophic conditions (e.g. Oocystis sp., Scenedesmus spp.) and were rather abundant during the first spring–autumn period of the lake’s refilling process. These complex microscopic communities are expected to shape highly dynamic and variable food webs with the risk of repeated fish kills.

Papadimitriou Th, Katsiapi M, Kormas KA, Moustaka-Gouni M, Kagalou I (2013) Artificially-born "killer" lake: phytoplankton based water quality and microcystin affected fish in a reconstructed lake. Sci. Tot. Environ. 452-453:116-124

ABSTRACT: Lake Karla (Greece) is an example of a lake ecosystem which was dried in 1960's and now is restored, facing various anthropogenic pressures, whereas it is also listed in the network of Greek protected areas in terms of its conservation value. The objective of the present study was to determine the presence of microcystins (MCYST) in the lake water and their accumulation in tissues of the commercial fish species Cyprinus carpio, along with the highlighting of phytoplankton community and general limnological features of Lake Karla, a newly reconstructed lake, the first year of its refilling. MCYST concentrations in water and fish tissues were determined by an enzyme-linked immunosorbent assay (ELISA). Results suggest that Lake Karla has undergone a progressive cultural eutrophication with frequent cyanobacterial blooms. The most dominant species in lake's phytoplankton were Anabaenopsis elenkiniiSphaerospermopsis and Planktothrix agardhii. MCYST concentrations were detected in water samples comparable to those reported for other eutrophicated Mediterranean lakes while considerable amounts of MCYST were detected in the tissues of the species C. carpio in the following order: liver > kidney > brain > intestine > muscles. The presence of prominent cyanobacterial blooms dominated by toxic species highlights the need to undertake eutrophication control measures so as to avoid further toxicological problems.

Sidiropoulos P, Mylopoulos N, Loukas A (2013) Optimal management of an overexploited aquifer under climate change: The Lake Karla case. Water Resour. Managem. 27:1635-1649

ABSTRACT: This paper presents a study for finding the optimal management plan of an overexploited aquifer under global climate change. The study area is the aquifer of the basin of Lake Karla, located in the eastern part of Thessaly in Greece. An optimization method has been used to evaluate the optimum volume of water that can be extracted from the aquifer and the optimum position of the wells with the objective of water table rise to a desirable sustainable level, taking into consideration the climate change forcing. The modelling system consists of a series of interlinked models: a hydrological, a lake-aquifer, a reservoir operation, a groundwater, and an optimization model. The climate change forcing on precipitation and temperature has been evaluated using the outputs of Canadian Centre for Climate Model Analysis General Circulation Model (CGCMa2) and a hybrid downscaling method which combines a multiple regression (MLR) model and a timeseries model for two socioeconomic emissions scenarios. The results of this study show that climate change plays an important role, as it affects the optimum volume of the extracted groundwater and the position of the irrigation wells.

Berillis P, Papadimitriou Th, Petridou E, Kormas KA, Kagalou I (2014) Histopathological findings in the brain and liver of Carassius gibelio from a newly reconstructed lake with toxic cyanobacteria. Turkish J. Fish. Aquat. Sci. 14:213-219

Lake Karla, Greece, is a partially reconstructed lake. The lake's water filling process started in September 2009. Existing evidence based on the prevailing microorganisms and cyanotoxin levels in the lake in 2010 suggested that the lake could have a negative effect on its biota. By investigating whether Carassius gibelio individuals bear brain and liver histopathological findings, this study complements the data now available from the first year of L. Karla's reconstruction. Based on the 16S rRNA gene diversity, the potentially toxic cyanobacteria Anabaenopsis sp. and Planktothrix were shown to be present in the lake's water in May 2011. C. gibelio specimens were collected a month later. Histopathological alterations in the liver of the individuals, namely picnotic nuclei, loss of structure and hemorrhagic regions, were detected by microscopic examination. Picnotic nuclei, loss of the liver structure and hemorrhagic regions were detected. These alterations may be associated with the occurrence of cyanobacterial toxins possibly produced by the potentially toxic cyanobacterial species found in the water column. No alterations were found in the brain, probably due to the existence of the blood-brain barrier.

Chamoglou M, Papadimitriou T, Kagalou I (2014) Key-descriptors for the functioning of a Mediterranean reservoir: The case of the new Lake Karla-Greece. Environ. Proc. 1:127-135

Mediterranean freshwater systems face the lack of water as an important threat along with other multiple stressors (e.g., eutrophication, salinization, changes in hydrology and morphology) mainly attributed to human intervention. These stressors have been maximized due to the climate variability, the progressive diminishing of freshwater availability and the topography characteristics. Lake Karla is an example of a lake ecosystem which was dried in the 1960s and now is restored, facing various anthropogenic pressures. During the last 2 years (2010–2012) a ‘new’ shallow lake was reconstructed experiencing extensive alterations associated with land use changes, hydrological flow modifications, over-enrichment of chemicals, inappropriate management of biological resources. In terms of conservation value, Lake Karla is listed in Natura 2000 sites as a protected area. The aim of the present paper is to identify the key-descriptors highlighting the function of the new system, thus providing necessary ‘tools’ for an effective management plan. A 12-month monitoring study has taken place revealing the hydrological profile, the excess of in-lake nutrient concentrations, mainly attributed to the inflows and surface runoff, thus promoting a cultural eutrophication as it is also expressed by the high chlorophyll values. Relationships between nutrients and chlorophyll-a concentrations highlight the system’s functioning. Yet, the classification of Lake Karla, as a highly modified water body, according to the Water Framework Directive, is discussed. Lake Karla serves as a paradigm on the multiple stressor effects and the complexity of biological restoration even though physical restoration has been established.

Papoutsa C, Akylas E, Hadjimitsis D (2014) Trophic state index derivation through the remote sensing of case-2 water bodies in the Mediterranean region. Open Geosci. 6:67-78

The main goal of this study is the derivation of Carlson’s Trophic State Index (TSI) through the remote sensing of four different Case-2 waters in the Mediterranean region such as Cyprus and Greece. TSISD is derived through extensive field ground campaign of Secchi Disk Depth measurements for the Asprokremmos Dam, located in Paphos District in Cyprus; Alyki Salt Lake, located in Larnaca District in Cyprus; and in Karla Lake, located in Volos District in Greece; and finally to three coastal water areas in the Limassol coastal area. Several regression models have been applied in order to develop the best regression model between the TSISD and in-band reflectance values for Landsat TM/ETM derived from spectroradiometric measurements using a GER-1500 field spectroradiometer over the main case study area in Asprokremmos Dam in Cyprus. Finally, we apply several regression models for Asprokremmos Dam for retrieving the suitable Landsat TM/ETM band or band combinations (obtained from field spectroradiometric measurements) in which TSISD can be determined. Indeed, the best regression model has been obtained by correlating ‘TSI Versus Band2/Band3’, with R2=0.89. All field TSISD and in-band reflectance values from the four different water bodies have been used to develop the best fitted model for the established TSISD Versus Band2/Band3 model. We find that the exponential regression model provides the best fitted equation over the four different water bodies.

2015 - present

Kormas KA, Meziti A, Papadimitriou T (2015) Microbiological confinement of two adjacent water wells in Lake Karla basin, Greece. Water 7:5272-5283

We analyzed the bacterial and archaeal community structure of two adjacent irrigation well waters of the Lake Karla Basin, Central Greece, in order to elucidate their connectivity or confinement by using 454 tag pyrosequencing of the 16S rRNA genes. Although considerable overlap was found at the phylum/high taxonomic level, and also at the operational taxonomic units (OTU) level, the dominant, and most likely active, prokaryotes represented by these OTUs were very different between the two wells. As expected, we found higher bacterial species richness compared to that of archaeal, and this renders Bacteria better for the study of connectivity or confinement of water wells. Some of the taxonomic groups found are amongst those found typically in the terrestrial subsurface and also those that have been recently described, enhancing the importance of the subsurface for expanding our knowledge on microbial diversity. The majority of the archaeal and several of the bacterial OTUs, including the most dominant ones in each well, were related to marine or saline environments, indicating the previously suggested persistence of fertilizer residuals in the basin’s soils.

Kungolos A, Emmanouil C, Manakou V, Darakas E (2015) Assessment of vulnerable freshwater ecosystems and various aquatic effluents by means of ecotoxicological assays. Desalin. Water Treat. 54:2120-2129

A battery of ecotoxicological assays of different trophic chain levels has been performed for water and sediment samples of two Greek vulnerable freshwater ecosystems (Karla Lake in Thessaly Region and Koronia Lake in Central Macedonia Region, respectively). These lakes, despite remediation programs, are still characterized by varied water quality. Furthermore, the quality of aquatic reservoirs aimed for human consumption as well as this of treated and untreated wastewater samples was also assessed through these bioassays. The outcome of the present research shows that condition of the studied lake ecosystems is still poor and intervention is needed for rectification of their continuous decline. Samples from treated municipal wastewater from the same regions were of medium to satisfactory quality, as measured by ecotoxicological assays. Despite causative relationships between burdened physicochemical parameters and increased toxicity, this toxicity could not always be attributed to these parameters. Results of bioassays in combination with standard physicochemical measurements of water samples may aid the integrated assessment of environmental risk arising from presence or release of these water samples in the ecosystem.

Mellios N, Kofinas D, Laspidou C, Papadimitriou T (2015) Mathematical modeling of trophic state and nutrient flows of Lake Karla using the PCLake model. Environ. Proc. 2:85-100

In the present article, we simulate Lake Karla, an important natural ecosystem under restoration in Greece, operating also as a reservoir. The lake trophic state is characterized as hypertrophic with the expected negative effects on biodiversity. The simulation of Lake Karla is a significant tool in terms of understanding, predicting and managing the ecosystem. We perform simulations using PCLake, a software package for shallow lakes, which provides a full set of parameters, modeling a wide range of physical, chemical and biological variables. The model is calibrated based on the time series of six variables for year 2012 and validated using data of years 2014–2015. We present the nutrient flow dynamics for year 2012 on a trimester basis, and investigate the interrelations of nutrient cycling and trophic state, through observed variables such as phycocyanin and chlorophyll-a concentrations, Carlson Trophic State Index and ratio of Dissolved Inorganic Nitrogen to Soluble Reactive Phosphorus.

ABSTRACT: A modeling system for the stochastic simulation and management of the overexploited groundwater resources of Lake Karla Basin in Central Greece is presented. The uncertainty of the hydrogeological environment which arises from the lack of the hydraulic conductivity data and aquifer’s heterogeneity necessitates the stochastic simulation of the underlying aquifer. For the conditional stochastic simulation of hydraulic conductivity, the geostatistical approach was used generating Monte-Carlo realizations. The impact of Lake Karla (or reservoir) restoration and the accompanying projects on the aquifer, is examined through various management scenarios taking into consideration this parameter uncertainty. The target of the restoration plan is to rehabilitate aquifer’s water table. This will be achieved through shutting down a great number of irrigation wells, as the irrigation needs of cultivations will be covered by the reservoir. The project with the highest environmental impact on the aquifer is the construction of 50 water supply wells at the lakeside zone of Lake Karla. Nowadays, due to the intense agricultural cultivation, the study area faces a serious water deficit problem, which has led to the over-exploitation of non-renewable groundwater and to a dramatic drawdown of aquifer’s water table. The results of the stochastic simulation and management indicates that the operation of the new water supply wells will lead, despite the operation of the new reservoir, to a further drawdown of aquifer’s water table, and will increase the effect of parameter uncertainty on hydraulic heads estimation by groundwater model.

ABSTRACT: In this research, the sediment quality of the recently reconstructed Lake Karla (central Greece) was evaluated by monitoring the nutrient loadings and heavy metal concentrations in 16 sites during the initial period of the lake’s rehabilitation. The results indicated that lake sediments exhibited a high nutrient status as manifested by the high loadings of organic carbon (OC), total nitrogen (TN) and available phosphorus (AP). Comparison of metal (Ni, Cr, Co, Zn, Cu and Pb) levels with sediment quality guidelines showed that Ni and Cr were found in concentrations well above the PEL (probable effect level) values. No correlations were found between the nutrients and the measured heavy metals. Multivariate analysis results implied that Ni, Cr, Co, Cu and Zn were controlled by natural geological sources whereas Pb might have an anthropogenic origin. The bioavailability ratios of metals followed a decreasing order of Pb > Cu ~ Co > Zn > Ni > Cr based on results obtained by a single 0.5 M HCl leach. Total and bioavailable concentrations of metals demonstrated significant seasonal variations but trends could not be generalized for all the elements. On the contrary, the nutrients did not show significant seasonal differences indicating that the lake sediments record the history of contamination with regard to nutrient status.

Aquatic Ecosystems and specially lakes are facing a vast number of human induced problems mainly interrelated to each other, affecting ecosystems in various ways. Thus, the "response" to specific management practices is often non- linear with noted large lag time. The interpretation and prediction of physical, chemical and biological functions taking place in freshwater ecosystems have been studied until today using widely available empirical and dynamic models and multi-criteria analysis methods. Among the new and promising analytical "tools" is the Fuzzy logic (fuzzy logic models) which contributes to the investigation of complex, non-linear and uncertain hydrosystems. The purpose of this study is to investigate the eutrophication factors in a highly variable system of Lake Karla (Thessaly).

Kopasakis K, Laspidou C, Spiliotopoulos M, Kofinas D, Mellios N (2016) Numerical investigation of wind driven circulation and horizontal dispersion in the surface sayer of a re-flooded shallow lake. Environ. Proc. 3:693-710

The re-flooded lakes with unique natural and cultural values that are under threat from anthropogenic pressure, consist a very important section of fresh water resources management in the Mediterranean. Lake Karla, positioned in the eastern part of Thessaly (Greece), is an example of a lake ecosystem, which was dried in the 60s to provide additional agricultural land; its restoration was launched in 2000 under the 3rd Community Support Framework. The object of the present paper is the study of the effect of the inflows, the wind action and the Coriolis action on the water circulation and the horizontal dispersion of the lake, using a three-dimensional hydrodynamic model. A number of wind directions have been tested upon the lake’s circulation, while in addition to winds other parameters, like inflow and Coriolis force, have been accounted for. Conservative computational tracers were used to assess the rate of horizontal dispersion from various locations in Lake Karla. The simulations indicated that in the coastal strip, the direction of the current corresponded to the wind direction. The horizontal dispersion rate is higher in the central region of the lake and it is not influenced by the presence of the inflow from Pinios River and the Coriolis action. The research in this paper will be useful in determining the horizontal transport of waterborne materials in the lake body which plays a major role in determining its biochemical status.

Mylopoulos N, Sidiropoulos P (2016) A stochastic optimization framework for the restoration of an over-exploited aquifer. Hydrol. Sci. J. 61:1691-1706

ABSTRACT: This study investigates the impact of hydraulic conductivity uncertainty on the sustainable management of the aquifer of Lake Karla, Greece, using the stochastic optimization approach. The lack of surface water resources in combination with the sharp increase in irrigation needs in the basin over the last 30 years have led to an unprecedented degradation of the aquifer. In addition, the lack of data regarding hydraulic conductivity in a heterogeneous aquifer leads to hydrogeologic uncertainty. This uncertainty has to be taken into consideration when developing the optimization procedure in order to achieve the aquifer’s sustainable management. Multiple Monte Carlo realizations of this spatially-distributed parameter are generated and groundwater flow is simulated for each one of them. The main goal of the sustainable management of the ‘depleted’ aquifer of Lake Karla is two-fold: to determine the optimum volume of renewable groundwater that can be extracted, while, at the same time, restoring its water table to a historic high level. A stochastic optimization problem is therefore formulated, based on the application of the optimization method for each of the aquifer’s multiple stochastic realizations in a future period. In order to carry out this stochastic optimization procedure, a modelling system consisting of a series of interlinked models was developed. The results show that the proposed stochastic optimization framework can be a very useful tool for estimating the impact of hydraulic conductivity uncertainty on the management strategies of a depleted aquifer restoration. They also prove that the optimization process is affected more by hydraulic conductivity uncertainty than the simulation process.

Papadimitriou T, Kormas K, Dionysiou DD, Laspidou C (2016) Using H2O2 treatments for the degradationof cyanobacteria and microcystins in a shallow hypertrophic reservoir. Environ.Sci. Pollut. Res. 23:21523-21535

ABSTRACT: Toxins produced by cyanobacteria in freshwater ecosystems constitute a serious health risk worldwide for humans that may use the affected water bodies for recreation, drinking water, and/or irrigation. Cyanotoxins have also been deemed responsible for loss of animal life in many places around the world. This paper explores the effect of H2O2 treatments on cyanobacteria and microcystins in natural samples from a hypertrophic reservoir in microcosm experiments. According to the results, cyanobacteria were more easily affected by H2O2 than by other phytoplanktonic groups. This was shown by the increase in the fractions of chlorophyll-a (a proxy for phytoplankton) and chlorophyll-b (a proxy for green algae) over total phytoplankton pigments and the decrease in the fraction of phycocyanin (a proxy for cyanobacteria) over total phytoplankton pigments. Thus, while an overall increase in phytoplankton occurred, a preferential decrease in cyanobacteria was observed with H2O2 treatments over a few hours. Moreover, significant degradation of total microcystins was observed under H2O2 treatments, while more microcystins were degraded when UV radiation was used in combination with H2O2. The combination of H2O2 and ultraviolet (UV) treatment in natural samples resulted in total microcystin concentrations that were below the World Health Organization limit for safe consumption of drinking water of 1 μg/L. Although further investigation into the effects of H2O2addition on ecosystem function must be performed, our results show that the application of H2O2 could be a promising method for the degradation of microcystins in reservoirs and the reduction of public health risks related to the occurrence of harmful algal blooms.

Sidiropoulos P, Mylopoulos N, Loukas A (2016) Reservoir-aquifer combined optimization for groundwater restoration: The case of Lake Karla watershed, Greece. Wat. Util. J. 12:17-26

ABSTRACT: The implementation of environmental projects, which has been very successful when restoring degraded water resources, is by itself not enough. The optimum combined operation of artificial water resources and natural systems, plays a crucial role in achieving sustainable management. This study presents a methodology for the simulation and optimization of Lake Karla watershed groundwater use for domestic water supply and irrigation, under two constraints of groundwater restoration. This is achieved by using a coupled modeling system of artificial and natural water resources simulation and a conjunctive groundwater optimization-simulation model. The groundwater flow model simulates the operation of the alluvial phreatic aquifer under different groundwater management scenarios. The management model GWM estimates the optimum pumping rates, the number and the locations of irrigation and domestic water supply wells. Optimal pumping rates were inserted into the groundwater flow model and the hydraulic head maps of the aquifer and the volumetric budget was estimated. Four alternative management scenarios for the location of 40 water supply wells for the city of Volos have been studied and optimized. These water supply wells are part of the Lake Karla restoration project and they will be located at the southern part of the aquifer, where the greatest drawdown of the water table has been observed. The management scenarios were evaluated regarding the two environmental constraints of groundwater rehabilitation and the optimal groundwater use.

Theologou I, Kagalou I, Papadopoulou MP, Karantzalos K (2016) Multitemporal mapping of chlorophyll–α in Lake Karla from high resolution multispectral satellite data. Environ. Proc. 3:681-691

With the aquatic environments being excessively stressed by human activities, the need for monitoring critical quality parameters continuously and at large spatial scales is greater than ever. Tο this end, the goal of this study was to exploit remote sensing data for water quality estimation towards the development of a long-term monitoring protocol for aquatic systems. High resolution, multitemporal data were employed along with in-situ measurements for key water quality parameters. After establishing relations between the satellite and in-situ data, multitemporal geospatial maps of Lake Karla were produced and validated, indicating that the observed chlorophyll-α is fluctuating throughout the year. In particular, a high correlation rate (r2 > 89 %) for Chl-a was derived through a linear regression model while certain mismatches occurred due to frequent cyanobacterial blooms that were mainly observed in the quite shallow parts of the lake. Moreover, the spatiotemporal analysis revealed a gradual slight decline in average chlorophyll-α concentrations from the beginning of 2011 and onward. The lake regions which were affected the most were the shallow ones, so it is necessary to better distribute the sampling locations within the lake in order to better quantify the fluctuations of water quality parameters. By exploiting high resolution satellite imagery, the proposed methodology implements a low-cost water monitoring system which enables the frequent update of important water quality parameters of any relevant geo-database, towards the efficient development of water management plan for protection and restoration of sensitive aquatic ecosystems.

ABSTRACT: The effects of climate change on meteorology, hydrology and ecology have become a priority area for research and for water management. It is crucial to identify, simulate, evaluate and, finally, adopt water resources management strategies to overturn the impacts of climate change. This paper is dealing with the assessment of climate change impacts on the availability of water resources and the water demands and the evaluation of water resources management strategies in the Lake Karla watershed, central Greece and it is a contribution to the “HYDROMENTOR” research project. The outputs of the Canadian Centre for Climate Modelling Analysis Global Circulation Model CGCM3 were downscaled using a statistical hybrid method to estimate monthly precipitation and temperature time series for present and future climate periods. The analysis was conducted for two future periods 2030–2050 and 2080–2100 and three SRES scenarios (A2, A1B and B1). The surface water and groundwater have been simulated for present and future climate periods using a modelling system, which includes coupled hydrologic models. Two operational strategies of hydro-technical project development are coupled with three water demand strategies. Overall, eight water management strategies are evaluated for present climate conditions and twenty four water management strategies for future climate conditions have been evaluated. The results show that, under the existing water resources management, the water deficit of Lake Karla watershed is large and it is expected to become critical in the future, even though the impact of climate change on the meteorological parameters is very moderate.

Ellina G, Papaschinopoulos G, Papadopoulos BK (2017) Fuzzy inference systems: selection of the most appropriate fuzzy implication from available lake water quality statistical data. Environ. Proc. 4:923-935

ABSTRACT: To this day, models such as empirical and dynamic, along with the multi-criteria analysis methods, have helped us towards the very understanding and estimation of all the functions (physical, chemical, biological) existing in freshwater ecosystems. The rich and variable system of the Greek lake Karla is a perfect candidate for our study and its purpose, which is to investigate the factors responsible for eutrophication (water temperature, nitrates, total phosphorus, secchi depth, chlorophyll-a) using fuzzy logic. In fuzzy logic, where the proposition can take any value in the close interval [0,1], there are infinite numbers of fuzzy implications which can be used; hence, a method of selecting the most appropriate implication is required. In this paper, we propose a method of evaluating fuzzy implications using available statistical data. The choice of the appropriate implication is based on the deviation of the true value of the fuzzy implication from the real values, as described by the statistical data.

Gkelis S, Panou M, Chronis I, Zervou S-K, Christophoridis C, Manolidi K, Ntislidou C, Triantis TM, Kaloudis T, Hiskia A, Kagalou I, Lazaridou M (2017) Monitoring a newly re-born patient: water quality and cyanotoxin occurrence in a reconstructed shallow Mediterranean lake. Adv. Oceanogr. Limnol. 8:33-51

Lake Karla (Central Greece) is a unique example - at European scale - of a shallow lake ecosystem that was dried in the 1960s and in 2009 started to be restored. The lake is listed in the network of the Greek protected areas as it is considered a vital aquatic ecosystem, in terms of biodiversity. It has, however, already been adversely affected by both agricultural and industrial land uses in the surrounding area, leading to eutrophication and shifting algal community towards bloom-forming toxic cyanobacterial species. After repeated heavy-blooms, cyanotoxin occurrence and mass fish kills, the local ecosystem management authority has implemented a water quality monitoring program (July 2013 - July 2015) to assess environmental pressures and the response of aquatic biota in the lake. Microscopic, immunological, and molecular techniques combined with physico-chemical parameters, complemented by liquid chromatography tandem mass spectrometry (LC-MS/MS), were used to monitor cyanobacteria blooms and the associated cyanotoxin production from three different sites in Lake Karla and from the adjacent Kalamaki Reservoir. Water quality was also assessed by the structure of benthic invertebrate community on the sediment. Cyanobacteria were the main phytoplankton component, representing more than 70% of the total phytoplankton abundance; dominant taxa belonged to Cylindrospermopsis raciborskiiLimnothrix redekeiAnabaenopsis elenkinii, and Microcystis spp. Euglenophytes (Euglena), diatoms (Nitzschia), and chlorophytes (Scenedesmus) were also important phytoplankton constituents. LC-MS/MS confirmed the co-occurrence of microcystins, cylindrospermopsin, saxitoxin, neo-saxitoxin and anatoxin-a. The occurrence of cyanotoxins in relation to the persistent and dominant cyanobacteria and the impact of cyanobacterial harmful algal blooms on the newly constructed lake along with the land uses and the emergent mitigation measures are discussed.

Laspidou C, Kofinas D, Mellios N, Latinopoulos D, Papadimitriou T (2017) Investigation of factors affecting the trophic state of a shallow Mediterranean reconstructed lake. Ecol. Engineer. 103:154-163

ABSTRACT: In this article, we focus on shallow sub-tropical lakes and study the factors that determine their trophic state and food web structure. We use the model PCLake to simulate lake nutrient dynamics and investigate key factors causing eutrophication, such as in-lake nutrient cycling, long residence time and low depths. Modeling results are validated in a reconstructed lake that is also used as a reservoir located in central Greece. Various operational scenarios and their effect on lake trophic state are explored. A climate change scenario is also presented, showcasing its influence on lake nutrient dynamics and food web structure. Our results confirm that lake residence time, lake depth and nutrient inflows are the factors that determine the lake trophic state, while climate change seems to slightly intensify the mechanisms that establish lake eutrophic conditions.

Levizou E, Statiris G, Papadimitriou Th, Laspidou CS, Kormas KA (2017) Lettuce facing microcystins-rich irrigation water at different developmental stages: effects on plant performance and microcystins bioaccumulation. Ecotoxicol. Environ. Safety 143:193-200

ABSTRACT: This study investigated the microcystins (MCs)-rich irrigation water effect on lettuce of different developmental stages, i.e. during a two months period, covering the whole period from seed germination to harvest at marketable size of the plant. We followed four lettuce plant groups receiving MCs-rich water (1.81μgl-1 of dissolved MCs), originating from the Karla Reservoir, central Greece: 1) from seeds, 2) the cotyledon, 3) two true leaves and 4) four true leaves stages, all of which were compared to control plants that received tap water. Lettuce growth, photosynthetic performance, biochemical and mineral characteristics, as well as MCs accumulation in leaves, roots and soil were measured. The overall performance of lettuce at various developmental stages pointed to increased tolerance since growth showed minor alterations and non-enzymatic antioxidants remained unaffected. Plants receiving MCs-rich water from the seed stage exhibited higher photosynthetic capacity, chlorophylls and leaf nitrogen content. Nevertheless, considerable MCs accumulation in various plant tissues occurred. The earlier in their development lettuce plants started receiving MCs-rich water, the more MCs they accumulated: roots and leaves of plants exposed to MCs-rich water from seeds and cotyledons stage exhibited doubled MCs concentrations compared to respective tissues of the 4 Leaves group. Furthermore, roots accumulated significantly higher MCs amounts than leaves of the same plant group. Concerning human health risk, the Estimated Daily Intake values (EDI) of Seed and Cotyledon groups leaves exceeded Tolerable Daily Intake (TDI) by a factor of 6, while 2 Leaves and 4 Leaves groups exceeded TDI by a factor of 4.4 and 2.4 respectively. Our results indicate that irrigation of lettuce with MCs-rich water may constitute a serious public health risk, especially when contaminated water is received from the very early developmental stages (seed and cotyledon). Finally, results obtained for the tolerant lettuce indicate that MCs bioaccumulation in edible tissues is not necessarily coupled with phytotoxic effects.

ABSTRACT: In this paper, the restoration of Lake Karla's ecosystem is studied through the evaluation of its current status. Lake Karla was one of the most important wetlands of Greece with many benefits not only to biodiversity preservation, to water balance of the watershed, but also to local economy in terms of fisheries. Its drainage, in 1962, created a lot of environmental problems and led to the local economy shrinking. After its refilling, the newly re-established water body is considered a vital aquatic ecosystem since it is listed in the network of Natura 2000. The monitoring results, the pressures and their causes that affected the restoration effort are presented. The assessment of the water quality is achieved by evaluating the results of the monitoring and fieldwork programs that Management Body of Eco-development Area of Lake Karla has performed during the last four years funded by the European Union. The results indicate strong eutrophication along with threats to biodiversity. The delay of implementation of Lake Karla reconstruction project, the decline from the proposed Environmental Terms and the lack of environmental policy are the most important causes of pressures.

Papadimitriou T, Katsiapi M, Vlachopoulos K, Christopoulos A, Laspidou C, Moustaka-Gouni M, Kormas KA (2018) Cyanotoxins as the “common suspects” for the Dalmatian pelican (Pelecanus crispus) deaths in a Mediterranean reconstructed reservoir. Environ. Pollut. 234:779-787

ABSTRACT: Toxic cyanobacterial blooms have been implicated for their negative consequences on many terrestrial and aquatic organisms. Water birds belong to the most common members of the freshwater food chains and are most likely to be affected by the consumption of toxic cyanobacteria as food. However, the contribution of cyanotoxins in bird mortalities is under-studied. The aim of the study was to investigate the likely role of cyanotoxins in a mass mortality event of the Dalmatian pelican (Pelecanus crispus) in the Karla Reservoir, in Greece. Water, scum, tissues and stomach content of dead birds were examined for the presence of microcystins, cylindrospermopsins and saxitoxins by an enzyme-linked immunosorbent assay. High abundances of potential toxic cyanobacterial species and significant concentrations of cyanotoxins were recorded in the reservoir water. All examined tissues and stomach content of the Dalmatian pelicans contained significant concentrations of microcystins and saxitoxins. Cylindrospermopsin concentrations were detected in all tissues except from the brain. Our results suggest that cyanotoxins are a plausible cause for this bird mass mortality episode in the Karla Reservoir.

Bobori DC, Ntislidou C, Petriki O, Chronis I, Kagalou I, Lazaridou M (2018) Macroinvertebrate and fish communities in the watershed of a re-constructed Mediterranean water body: link to the ecological potential. Environ. Monitor. Assess. 190,106

ABSTRACT: The role of benthic macroinvertebrate and fish communities for assessing the ecological quality of an artificial re-constructed, after 50 years of dryness, Mediterranean water body (Karla Reservoir, Greece) is presented. Moreover, we provide knowledge on the structure of the biological communities and their functioning role, for inspiring feature actions that will contribute to biodiversity protection and ecosystem services. Water (physicochemical parameters), benthic macroinvertebrates, and fish were monitored during a 2-year survey (2013–2015) in Karla and Kalamaki reservoirs and the inflowing ditches. A clear temporal pattern was evident for all sampling stations studied, differentiating the low- and high-flow period samples as to their physicochemical parameters. Redundancy analysis (RDA) revealed NO3-N, total nitrogen and total dissolved phosphorous as the most significant environmental parameters in explaining benthic invertebrate variance in ditches. Generally, tolerant to organic pollution macroinvertebrate taxa were abundant in ditches and reservoirs, while the fish fauna in Karla was composed almost exclusively of planktivorous and invertivorous species. Macroinvertebrate (GLBiI) and fish (GLFI) indices classified the ecological quality of Karla Reservoir as “poor” while ditches were classified as “bad” according to HESY-2. The anthropogenic pressures applied in the catchment and the benefits of improving water quality are discussed in the context of the implementation of Water Framework Directive 2000/60/EC for introducing sustainable management plans, taking into account some ecological restoration principles.

Last updated: 06 Feb. 2018