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Establishing Total Phosphorus Boundaries to Support Good Ecological Status of Greek Lakes and Reservoirs in Accordance with the Water Framework Directive
(2025-11-24)
M. Zioga
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D. Kemitzoglou
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I. Zerva
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S. Katsavouni
;
I.Kagalou
Eutrophication, driven by nutrient enrichment, represents substantial anthropogenic pressure with harmful consequences for aquatic ecosystems. TheWater Framework Directive provides a structured approach to addressing this challenge as it requires European Union Member States to achieve at least good ecological status for their surface waters. The establishment of realistic nutrient boundaries, above which negative effects become pronounced, is essential to guide regulatory intervention aimed at securing long-term water sustainability in Europe. Greece is one of the Member States which should determine nutrient boundaries supporting the good ecological status of lakes. Two statistical approaches, ranged major axis regression and binomial logistic regression, were applied for setting appropriate nutrient boundaries for Greek natural lakes and reservoirs, using datasets of phytoplankton and total phosphorus concentrations, retrieved from the national monitoring program (2016–2023). The predicted boundary values for total phosphorus supporting good ecological status ranged from 32 to 76 μg/L, with stricter boundaries corresponding to deep lakes. Nutrient boundaries that reflect the environmental pressures on Greek natural lakes and reservoirs are fundamental to ensure proper design of lake management strategies.
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Spatio-temporal changes of littoral macrophytes along hydrological conditions in Yliki, a Greek lake
(2025-11-24)
E. Mavromati
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V. Giourieva
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D. Papadimos
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A. Apostolakis
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V. Tsiaoussi
Human-induced changes in hydrological conditions seem to be among the main factors affecting ecological relationships in lakes (Zhao et al., 2021). Water level fluctuation (WLF), which is often attributed to anthropogenic activities and its amplitude variations can have an impact on aquatic plant communities by altering several key environmental factors (Hill et al., 1998, Zhao et al., 2021). These fluctuations influence water depth, underwater irradiance, water quality, and dissolved oxygen levels, all of which play crucial roles in the growth and survival of macrophytes (Li et al., 2017). The interplay of these factors can significantly change the growing conditions for several macrophyte species over time. To overcome this, macrophytes have evolved to adjust gradually to periodic WLF over time, as part of their long-term evolutionary process (Zhao et al., 2021). The aims of the study are to present the results of WLF over time in Lake Yliki, study its aquatic plant community and explore the effect of WLFs on macrophytes.
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Spatio-temporal changes of littoral macrophytes along hydrological conditions in Yliki, a Greek lake (Presentation)
(2025-11-18)
E. Mavromati
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V. Giourieva
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D. Papadimos
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A. Apostolakis
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V. Tsiaoussi
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Bathymetry and morphometric analysis of Greek natural lakes through a hybrid GIS-acoustic methodology
(2025-04-03)
T. Perivolioti
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A. Apostolakis
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D. Papadimos
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V. Tsiaoussi
Homogeneous and up-to-date bathymetric information on lakes is essential to improve limnological knowledge and produce evidence-based lake monitoring, assessment methods, and river basin management plans according to Water Framework Directive (WFD). The present study focused on the production of updated bathymetric information on the main natural Greek lakes and their morphometric analysis. The aim was to address the knowledge gap by providing updated homogeneous and accurate bathymetric information for the main freshwater natural lakes of Greece as part of the National Monitoring Network of Lakes in the context of WFD. We surveyed 14 freshwater lakes in mainland Greece using a dual frequency echosounder. Using the acoustic data collected during the surveys, bathymetric digital terrain models (DTMs) were produced for each lake and used to estimate morphometric characteristics (mean/ maximum depth, volume, lake depth ratio, volume development, mean lake diameter, relative depth ratio, shoreline development factor, hypsographic curve). This analysis demonstrated the potential of the morphometric approach to generate valuable information using up-to-date bathymetric DTMs. The geospatial data derived by the present study are available through an online repository, the Greek National Monitoring Network of Lakes (http://ekbygis.biodiversity-info.gr/geoserver/web/). These data provide a valuable database for the advancement of limnological knowledge, the implementation of comprehensive monitoring programmes, and informed decision making in water resources management.
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A Geographic Object-Based Image Approach Based on the Sentinel-2 Multispectral Instrument for Lake Aquatic Vegetation Mapping: A Complementary Tool to In Situ Monitoring
(2024-03-05)
M. Tompoulidou
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E. Karadimou
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A. Apostolakis
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V. Tsiaoussi
Aquatic vegetation is an essential component of lake ecosystems, used as a biological indicator for in situ monitoring within the Water Framework Directive. We developed a hierarchical object-based image classification model with multi-seasonal Sentinel-2 imagery and suitable spectral indices in order to map the aquatic vegetation in a Mediterranean oligotrophic/mesotrophic deep lake; we then applied the model to another lake with similar abiotic and biotic characteristics. Field data from a survey of aquatic macrophytes, undertaken on the same dates as EO data, were used within the accuracy assessment. The aquatic vegetation was discerned into three classes: emergent, floating, and submerged aquatic vegetation. Geographic object-based image analysis (GEOBIA) proved to be effective in discriminating the three classes in both study areas. Results showed high effectiveness of the classification model in terms of overall accuracy, particularly for the emergent and floating classes. In the case of submerged aquatic vegetation, challenges in their classification prompted us to establish specific criteria for their accurate detection. Overall results showed that GEOBIA based on spectral indices was suitable for mapping aquatic vegetation in oligotrophic/mesotrophic deep lakes. EO data can contribute to large-scale coverage and high-frequency monitoring requirements, being a complementary tool to in situ monitoring.
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Benthic macroinvertebrate communities in the littoral zone of Greek lakes
(Ελληνικό Κέντρο Βιοτόπων-Υγροτόπων (ΕΚΒΥ), 2023-11-22)
A. Patsia
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D. Kemitzoglou
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E. Mavromati
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V. Tsiaoussi
Greek natural lakes are discerned into three categories according to depth: very shallow lakes (GR-VSNL, mean depth< 3m), shallow lakes (GR-SNL, mean depth: 3-9 m) and deep lakes (GR-DNL, mean depth >9 m) (Kagalou et al., 2021). Lake zoobenthos is regularly examined for the classification of ecological status according to Water Framework Directive (WFD) (EU, 2000). Research objectives are to present the benthic macroinvertebrate communities in the Greek natural lakes, classify their ecological status & to investigate potential differences in benthic macroinvertebrate communities according to lake depth.
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Spatial and temporal variations of benthic macroinvertebrate communities in lake Kastoria, Nothern Greece
(2023-06-27)
A. Patsia
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D. Kemitzoglou
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E. Mavromati
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V. Tsiaoussi
Lake Kastoria, in northwestern Greece, is a shallow urban natural lake. The objectives of this study were a) to investigate spatial and temporal variations of benthic macroinvertebrate communities in Lake Kastoria and b) to assess the lake water quality with the use of a WFD-compliant national method. Samplings were undertaken at the littoral zone of the lake at 5 selected sites during spring 2017 and 2021, according to the Hellenic Lake Littoral Benthos (HeLLBI) assessment method. Non-metric multidimensional (NMDS) scaling and one-way analysis of similarity percentages were applied to visualize similarities and to identify the taxa responsible for the discrimination in benthic macroinvertebrate communities between different sampling periods, among sites and water quality classes. In total, 5569 individuals were collected and 37 taxa groups were identified. NMDS plot provided a useful display of the actual multivariate distance among samples (stress value: 0.14). Benthic invertebrate communities showed considerable spatial variation at local scale (sampling site level) except for one site but no clear temporal variation. The mean EQR value of HeLLBI showed moderate water quality of the lake. All sites showed no change in their water quality across time except for 2 sites that improved (poor to moderate and good respectively). Benthic macroinvertebrates communities at good water quality sites differed in composition and showed higher biodiversity compared to those at moderate and poor sites. Management measures should be site-adapted in Lake Kastoria and priority could be given to the conservation and restoration of the littoral zone.
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Mediterranean temporary ponds (habitat type 3170*) in the South Aegean Archipelago islands (Greece): filling the gaps
(2023-06-27)
E. Karadimou
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D. Kemitzoglou
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V. Tsiaoussi
Mediterranean temporary ponds (3170*, Directive 92/43/EEC) are scattered in the South Aegean islands (Greece). Their importance for biodiversity is great; they host plant and animal species depending exclusively or to a large extent on water, and form special habitats which act as "life refuges". At the same time, they support the agricultural activities of the local residents and provide multiple benefits. In this study, we focus on the identification, delineation and mapping of the Mediterranean temporary ponds, the description of the composition of their vegetation, their structure and functions, assessment of their conservation degree and recognition of the pressures they face. The 3170* habitat type was identified, recorded and studied in 42 locations, on 10 islands. Our results indicate that, in the South Aegean, despite the adverse climatic conditions, several small temporary ponds are preserved. They have a high degree of diversity in terms of their ecological, morphological and physico-chemical features. These are often natural wetlands with a high diversity of plant species, but in several cases, humans have artificially modified their abiotic, and hence biotic, characteristics. Most temporary ponds are altered under the pressure of long-term use of water, mainly in cultivations and grazing. Excavation, embankment and road openings bring about further degradation. In places undergoing tourist development, these risks increase. Strengthening their protection efforts, especially under the pressure of change in the climatic conditions, is essential for the conservation of Mediterranean temporary ponds.
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Does littoral substrate affect macroinvertebrate assemblages in Mediterranean lakes?
(2023-06-09)
E. Mavromati
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D. Kemitzoglou
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V. Tsiaoussi
The objective of this study was to investigate the effects of substrate type in macroinvertebrate assemblages in Mediterranean lakes. Samplings have taken place in the littoral zone of 21 lakes in Greece, between 2015 and 2018. We compared benthic macroinvertebrate assemblages among three substrate types of their littoral zones; sandy, covered with macrophytes and stony substrate. Benthic macroinvertebrate assemblages at sites with extended macrophyte cover differed only slightly in composition and abundance from the ones found in stony and sandy substrates. Coenagrionidae were indicative of sites covered with macrophytes and Oligochaeta and Erpobdellidae were representative of stony substrates. The type of substrate proved to be a statistically significant factor influencing the number of benthic macroinvertebrate taxa, the relative abundance of Oligochaeta and the relative abundance of Odonata. In the context of designing site-adapted management measures, priority could be given to the conservation and restoration of aquatic vegetation in lake littoral zones, which host rich macroinvertebrate assemblages with abundant taxa of Odonata.
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A new WFD—compliant littoral macroinvertebrate index for monitoring and assessment of Mediterranean lakes (HeLLBI)
(2021-10-25)
E. Mavromati
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D. Kemitzoglou
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V. Tsiaoussi
benthic macroinvertebrates is presented in this paper for classification of Greek natural lakes, in compliance with the requirements of Water Framework Directive (WFD). The method was developed based on the collection of littoral benthic invertebrate fauna and environmental data from 109 sampling sites in 21 natural lakes of the Greek National Water Monitoring Network. We focused the analysis on the effects of shore morphological alterations and eutrophication to the littoral invertebrate fauna, identified to family level, except oligochaetes, which were identified as a class, and more particularly to taxonomic composition and abundance, to taxa sensitivity,and to richness/diversity. Three metrics were included in the multimeric index: the relative abundance of Odonata classes, the Average Score per Taxon, and the Simpson’s diversity index. The metrics were converted to ecological quality ratios and ecological class boundaries were defined. The final multimetric index HeLLBI is expressed as an arithmetic average of normalized ecological quality ratios of the above metrics and a final score was assigned to each lake. Pressureresponse relationships of HeLLBI scores were statistically tested for morphological alterations, expressed as percentage of artificial shoreline, and eutrophication, expressed as total phosphorus. The HeLLBI scores correspond to ecological classes, according to WFD, and sampling sites with different ecological status contained distinct biological communities; those at high status where more diverse and with sensitive taxa and as the water quality deteriorated, macroinvertebrate assemblages consisted of fewer and more tolerant to degradation taxa. The HeLLBI method gave a reliable assessment of littoral benthic invertebrate fauna of Greek natural lakes and could be a useful tool for the classification of ecological status of other Mediterranean lakes.

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