Lake Ohrid Research Articles

Ostracod-based isotope record from Lake Ohrid (Balkan Peninsula) over the last 140 ka

The stable isotope composition of benthic ostracods from a deep-lake sediment core (JO2004-1) recovered from Lake Ohrid (Albania-Macedonia) was studied to investigate regional responses to climate change at the interface between the north-central European and Mediterranean climate systems. Ostracod valves are present only during interglacial intervals, during the Marine Isotope Stage (MIS) 5 and 1. The ostracod oxygen isotope values (δ 18O) quantitatively reflect changes in the oxygen isotope signal of the lake water (δ 18O L). The interpretation of this record however, is far from straight forward. δ 18O L variations throughout MIS 5/6 transition (TII), MIS 5 and MIS 1 appear to be controlled by site specific hydrological processes as shown by modern isotope hydrology. The δ 18O L trends at TII, MIS 5 and MIS 1 match the timing and the main structural feature of the major regional climate records (Corchia cave δ 18O, Iberian margin Sea Surface Temperature) suggesting that the Ohrid δ 18O L responded to global-scale climate changes, although it seems certain that the lake experienced a significant degree of evaporation and varying moisture availability. The carbon isotope signal (δ 13C) seems to respond more accurately to climate changes in agreement with other JO2004-1 proxies. δ 13C of the ostracod calcite is directly linked to the δ 13C of the dissolved inorganic carbon (DIC) in the lake, which in this case is controlled by the isotopic composition of the DIC in the incoming water and by the internal processes of the lake. High δ 13C during cold periods and low values during warm periods reflect changing vegetation cover and soil activity. These results suggest that Lake Ohrid has the potential to capture a long record of regional environment related-temperature trends during interglacial periods, particularly given the exceptional thickness of the lake sediment covering probably the entire Quaternary.

The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate

Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 14.7–6.9 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, followed by a post-Medieval loss of diversity which is consistent with cooling, but not definitive. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom accumulation data in future studies.

Native <i>Dreissena</i> freshwater mussels in the Balkans: in and out of ancient lakes

Abstract. The Balkans is a biogeographically highly diverse region and a worldwide hotspot of endemic freshwater diversity. A substantial part of this diversity is attributed to well recognized and potential ancient lakes in its southwestern part. However, despite considerable research efforts, faunal relationships among those lakes are not well understood. Therefore, genetic information from native representatives of the mussel genus Dreissena is here used to test the biogeographical zonation of the southwestern Balkans, to relate demographic changes to environmental changes, to assess the degree of eco-insularity, to reconstruct their evolutionary history, and to explore the potential of native taxa for becoming invasive. Phylogeographical and population genetic analyses indicate that most studied populations belong to two native species: D. presbensis (including the distinct genetic subgroup from Lake Ohrid, "D. stankovici") and D. blanci. In addition, the first confirmed record of invasive D. polymorpha in the southwestern Balkan is presented. The distribution of native Dreissena spp. generally coincides with the biogeographical zonations previously suggested based on fish data. However, there is disagreement on the assignment of the ancient lakes in the area to respective biogeographical regions. The data for Lake Ohrid are not conclusive. A closer biogeographical connection to lakes of the Vardar region and possibly the northern Ionian region is, however, suggested for Lake Prespa. The reconstruction of the evolutionary history of Dreissena spp. suggests that populations underwent demographic and spatial expansions in the recent past. Expansions started around 320 000–300 000 years ago in "D. stankovici", 160 000–140 000 years ago in D. blanci, and 110 000–70 000 years ago in D. presbensis. These time frames are discussed within the context of available paleogeological data for lakes Ohrid and Prespa. It is suggested that regional environmental changes may have had pronounced effects on the population histories of native Dreissena spp., though the high buffer capacity of Lake Ohrid may have lessened these effects in "D. stankovici". In addition, local events influencing individual lakes had very likely considerable effects on the demographic histories of Dreissena spp. as well. The observed patterns of immigration and emigration in and out of ancient lakes may suggest that limited gene flow enabled the survival of few isolated subpopulations and that later on eco-insularity (selective advantages of locally adopted groups) may have prevented excessive hybridization and sympatry of closely related taxa. As for the potential invasiveness of native Dreissena spp., the inferred spatial expansions are not human-mediated and all taxa still appear to be restricted to their native ranges. A concern, however, is that today D. presbensis and D. blanci also occur in artificial water bodies, and that invasive D. polymorpha has reached the area.

The Late Holocene to Pleistocene tephrostratigraphic record of Lake Ohrid (Albania)

We present in this work a tephrostratigraphic record from a sediment piston core (JO 2004) from Lake Ohrid. Five tephra layers were recognised, all from explosive eruptions of southern Italy volcanoes. A multidisciplinary study was carried out, including stratigraphy, AMS 14C chronology and geochemistry. The five tephra layers were correlated with terrestrial proximal counterparts and with both marine and lacustrine tephra layers already known in the central Mediterranean area. The oldest is from Pantelleria Island (P11, 131 ka BP). Other three tephra layers are from Campanian volcanoes: X6, Campanian Ignimbrite-Y5 and SMP1-Y3 (107, 39 and 31 ka BP respectively). The youngest tephra layer corresponds to the FL eruption from Etna Volcano (3.4 ka BP). In three cases these recognitions confirm previous findings in the Balkans, while two of them were for the first time recognised in the area, with a significant enlargement of the previous assessed dispersal areas.

Diversity and dynamics of the fungal community in Lake Ohrid

Fungi are universally present in freshwater systems and are of great significance in the structural and functional organization of these ecosystems. The aim of this study was to assess the diversity of fungal communities in the ancient, oligotrophic Lake Ohrid and to investigate their spa- tial and temporal dynamics. The fungal community in Lake Ohrid consists of 36 species identified from 213 isolates. The autochthonous community is made up of 10 species belonging to the orders Saprolegniales and Peronosporales: Achlya americana, A. racemosa, Aphanomyces leavis, Dic- tyuchus monosporus, D. sterile, Pythium ultimum, Saprolegnia ferax, S. hypogina, S. monoica, and Saprolegnia sp. The allochthonous community is composed of 26 species from 15 genera of fungi. The dominant genera are Aspergillus (5 species, 13.86% of determined species), Penicillium (6 species, 16.66%), and Cladosporium and Fusarium (3 species, 8.33%). The species Kloeckera apiculata, Didiostible sp., Gliocladium roseum, and Varicosporium delicatum are identified here for the first time in freshwater ecosystems of the Balkans. Quantitative analysis of the fungal community showed that the number of propagules varied in the range of 0 to 19.5 × 10 3 l -1 . The diversity and abundance of both the autochthonous and the allochthonous fungal communities are greater in the littoral than in the pelagial zone. Our results represent the first hydromycological data for Lake Ohrid the region of Macedonia.

A comparative study of Reimeria species (Bacillariophyceae)

Abstract: A study of five Reimeria taxa was performed based on light microscopy (LM) and scanning electron microscopy (SEM). The new species Reimeria fontinalis Levkov sp. nov. from Lake Ohrid (Macedonia) was compared to similar taxa, R. sinuata (W.Gregory) Kociolek & Stoermer and R. ovata (Hustedt) Levkov & Ector stat. nov. Reimeria fontinalis is closely related to the R. sinuata complex because of its biseriate striae and the apical pore fields that do not extend onto the valve face. The main morphometric features distinguishing R. fontinalis from other species of Reimeria [R. capitata (Cleve-Euler) Levkov & Ector comb. nov. stat. nov., R. sinuata, R. uniseriata S.E.Sala, J.M.Guerrero & Ferrario] are valve outline, size and stria density. Reimeria fontinalis is widely distributed in epipsammic diatom assemblages in Lake Ohrid and surrounding springs.

Nuclear and mitochondrial DNA sequence data reveal the evolutionary history of Barbus (Cyprinidae) in the ancient lake systems of the Balkans

Freshwater fauna of ancient lakes frequently contain endemic taxa thought to have originated during the long existence of these lakes, yet uncertainties remain as to whether they represent distinct genetic lineages with respect to more widespread relatives and to the relative roles of isolation and dispersal in their evolution. Phylogenetic analyses of sequence variation at nuclear and mitochondrial genes were used to examine these issues for the freshwater fish genus Barbus in two European ancient lake systems on the Balkan Peninsula. The nuclear and mitochondrial data yielded concordant phylogeographic patterns though incomplete sorting of nuclear haplotypes between some mitochondrial clades was detected. The distributions of two currently recognized species investigated here do not match the distributions of evolutionary lineages revealed by phylogenetic analyses. The Prespa barbel, Barbus prespensis, is not endemic to the lakes Prespa as previously thought but is instead found to be widespread in the south-eastern Adriatic Sea basin, with a distribution largely corresponding to the basin of the now extinct Lake Maliq historically connected with Lake Prespa. On the other hand, a cryptic phylogenetic subdivision in a widespread species, B. rebeli, was discovered to be more distant from B. rebeli than from other Barbus species and to be endemic to the system of connected lakes Ohrid and Shkodra. The division coincides with the hydrogeographical boundary delimiting distributions of other freshwater fishes, and we suggest that this newly discovered evolutionary lineage represents a distinct species. These findings support the emerging pattern that endemic taxa have evolved not through isolation of individual lakes, but in systems of currently and historically interconnected lakes and their wider basins.

Lake Ohrid, Albania, provides an exceptional multi-proxy record of environmental changes during the last glacial–interglacial cycle

Multi-proxy analyses on core JO2004-1 recovered from Lake Ohrid (40°55.000 N, 20°40.297E, 705 m a.s.l.) provide the first environmental and climate reconstruction in a mountainous area in Southern Europe over the last 140,000 years. The response of both lacustrine and terrestrial environments to climate change has been amplified by the peculiar geomorphological and hydrological setting, with a steep altitudinal gradient in the catchment and a karstic system feeding the lake. The karstic system was active during interglacials, leading to high carbonate production in the lake, and blocked during glacials as a result of extremely cold climate conditions with permafrost in the mountains. At the Riss–Eemian transition (Termination 2) the increase in lacustrine productivity predated forest expansion by about 10,000 years. In contrast, the Late Glacial–Holocene transition (Termination 1) was characterized by the dramatic impact of the Younger Dryas, which initially prevented interglacial carbonate production and delayed its maximum until the mid-Holocene. In contrast, forest expansion was progressive, starting as early as ca. 38,000 ago. The proximity of high mountains and the probable moderating lake effect on local climate conditions promoted forest expansion, and contributed to make the surroundings of Lake Ohrid favourable to forest refugia during the last glacial, usually steppic, period. Our study of sedimentology, mineralogy, geochemistry, magnetics, palynology and isotopes illustrates the non-linear response of terrestrial and lacustrine ecosystems to similar climate events, and demonstrates the potential of Lake Ohrid as an excellent paleoclimatic archive during the Quaternary.

A paleoclimate record with tephrochronological age control for the last glacial-interglacial cycle from Lake Ohrid, Albania and Macedonia

Lake Ohrid is probably of Pliocene age, and the oldest extant lake in Europe. In this study climatic and environmental changes during the last glacial-interglacial cycle are reconstructed using lithological, sedimentological, geochemical and physical proxy analysis of a 15-m-long sediment succession from Lake Ohrid. A chronological framework is derived from tephrochronology and radiocarbon dating, which yields a basal age of ca. 136 ka. The succession is not continuous, however, with a hiatus between ca. 97.6 and 81.7 ka. Sediment accumulation in course of the last climatic cycle is controlled by the complex interaction of a variety of climate-controlled parameters and their impact on catchment dynamics, limnology, and hydrology of the lake. Warm interglacial and cold glacial climate conditions can be clearly distinguished from organic matter, calcite, clastic detritus and lithostratigraphic data. During interglacial periods, short-term fluctuations are recorded by abrupt variations in organic matter and calcite content, indicating climatically-induced changes in lake productivity and hydrology. During glacial periods, high variability in the contents of coarse silt to fine sand sized clastic matter is probably a function of climatically-induced changes in catchment dynamics and wind activity. In some instances tephra layers provide potential stratigraphic markers for short-lived climate perturbations. Given their widespread distribution in sites across the region, tephra analysis has the potential to provide insight into variation in the impact of climate and environmental change across the Mediterranean.

Preliminary Investigations on Odonata from the Lake Ohrid (Macedonia)

ABSTRACTThere is much information about odonates in lakes in the whole Europe. The lack of data about this group of invertebrates in the Lake Ohrid—the UNESCO natural and cultural heritage is unusual. The aim of our paper is to cover that field. Material included 17 species and 476 specimens of only adult Odonata, which was collected in June 2009 year on 21 stations of the Lake Ohrid. Such number of species is not very high and appears in low differential of phyto-littoral of the lake. The most numerous species is Enallagma cyathigerum, which is widespread and associated with nymphaeid and elodeid plant species. Such big number of individuals the species is supported by a large belt of elodeids (Potamegeton perfoliatus) occurring in the Lake Ohrid. Four odonates belong to South-European species; the other ones are widespread European species. Probably the reason is position of the Lake Ohrid in the mountains, which made climate more moderate.

Important Bird Areas in Macedonia: Sites of Global and European Importance

Important Bird Areas in Macedonia: Sites of Global and European Importance

Monogenean Trematods of Chub Leuciscus Cephalus Albus Bonaparte, 1838 from the Lake Ohrid (Macedonia)

ABSTRACTDuring the parasitological investigations on the gills of Leuciscus cephalus albus from Lake Ohrid (Macedonia), are found 4 monogenean species: Dactylogyrus sphyrna, Dactylogyrus folkmanovae, Dactylogyrus vistulae and Paradiplozoon ergensi. The total prevalence of infestation is 58,0% and the highest prevalence is of Dactylogyrus sphyrna (found in 26,0% of chubs). The average intensity of infestation is 5,50, and the highest level is that of Paradiplozoon ergensi. All monogenean species mentioned in this study represents a first record for the fishes from natural lakes in Macedonia, with the exception of Paradiplozoon ergensi, previously found in the Lake Ohrid. Among the monogenean species, found out in Lake Ohrid, the greatest pathological influence is associated with Dactylogyrus vistulae and Paradiplozoon ergensi.

Erste dendrochronologische Datierungen historischer Hölzer in Albanien

The dendrochronological investigations were conducted primarily on timber from the region of Korca in the south-east of Albania. The samples come from recent trees, from churches, secular buildings, icons and from the piles of prehistoric settlements on the shore of the Great Prespa Lake and on the Macedonian side of Lake Ohrid. The majority of the 564 samples come from conifers, in particular European Black Pine (Pinus nigra), Bosnian Pine (Pinus heldreichii), fir (Abies sp.) and in prehistoric times also juniper ( Juniperus sp.). So far it has only been possible to sample wood from deciduous trees like beech (Fagus sp.) and oak (Quercus sp.) on a much smaller scale. The samples enable us to establish median series of annual growth rings from the Neolithic (6 th millennium), middle Bronze Age (3 rd millennium), the Middle Ages and the modern era. Absolute datings are at the moment sufficient only for timber finds from the last 1000 years. So far, 219 annual growth ring series from 36 icons and seven buildings have been dated. The contribution also discusses aspects of climate history, the history of building and art, and historical forms of forest utilization. The continuation of these investigations is contributing significantly to the development of an absolute chronological framework for the region south and south-east of the Alps.

The Holocene tephrostratigraphic record of Lake Shkodra (Albania and Montenegro)

AbstractTwo cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present‐day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked‐eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under‐saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma‐Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight 14C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd.

A tephrostratigraphic record for the last glacial–interglacial cycle from Lake Ohrid, Albania and Macedonia

AbstractHere we present a tephrostratigraphic record (core Co1202) recovered from the northeastern part of Lake Ohrid (Republics of Macedonia and Albania) reaching back to Marine Isotope Stage (MIS) 6. Overall ten horizons (OT0702‐1 to OT0702‐10) containing volcanic tephra have been recognised throughout the 14.94 m long sediment succession. Four tephra layers were visible at macroscopic inspection (OT0702‐4, OT0702‐6, OT0702‐8 and OT0702‐9), while the remaining six are cryptotephras (OT0702‐1, OT0702‐2, OT0702‐3, OT0702‐5, OT0702‐7 and OT0702‐10) identified from peaks in K, Zr and Sr intensities, magnetic susceptibility measurements, and washing and sieving of the sediments. Glass shards of tephra layers and cryptotephras were analysed with respect to their major element composition, and correlated to explosive eruptions of Italian volcanoes. The stratigraphy and the major element composition of tephra layers and cryptotephras allowed the correlation of OT0702‐1 to AD 472 or AD 512 eruptions of Somma‐Vesuvius, OT0702‐2 to the FL eruption of Mount Etna, OT0702‐3 to the Mercato from Somma‐Vesuvius, OT0702‐4 to SMP1‐e/Y‐3 eruption from the Campi Flegrei caldera, OT0702‐5 to the Codola eruption (Somma‐Vesuvius or Campi Flegrei), OT0702‐6 to the Campanian Ignimbrite/Y‐5 from the Campi Flegrei caldera, OT0702‐7 to the Green Tuff/Y‐6 eruption from Pantelleria Island, OT0702‐8 to the X‐5 eruption probably originating from the Campi Flegrei caldera, OT0702‐9 to the X‐6 eruption of generic Campanian origin, and OT0702‐10 to the P‐11 eruption from Pantelleria Island. The fairly well‐known ages of these tephra layers and parent eruptions provide new data on the dispersal and deposition of these tephras and, furthermore, allow the establishment of a chronological framework for core Co1202 for a first interpretation of major sedimentological changes. Copyright © 2009 John Wiley & Sons, Ltd.

Climate controlled ostracod preservation in Lake Ohrid (Albania, Macedonia)

Lake Ohrid (Albania, Macedonia) is probably the oldest existing lake in Europe and thus of great interest for palaeo-environmental and genetic studies. Within more than 220 endemic faunal species known to live in the lake, ostracods are outstanding due to the potentially very long fossil record. They can provide geochemical information over a period exceeding the entire Quaternary and direct evidence for radiation. Here we discuss the ostracod record and the calcite concentration along a 10-m-long sediment core taken at 100 m water depth in the south-eastern, Albanian part of Lake Ohrid. Well preserved ostracod valves representing in-situ fauna only occur from 0 cm to 105 cm and from 476 cm to 933 cm core depth, corresponding to the last interglacial and the Holocene, respectively. Those periods are also characterized by high concentrations of endogen calcite. There is no significant difference in the faunal composition of the two periods separated by several tens of thousand years and we found non-calcitic ostracod remains, especially the strongly chitinised mandibles, throughout the glacial period. Therefore, we conclude that ostracods were present in the lake throughout the entire period represented by the sediment core, but with poor or lacking preservation of their calcite valves during the glacial period. Calcite precipitation and ostracod preservation were most likely inhibited by the complete interruption of Calcium supply from karsts springs, which were inactive during the glacial periods due to permafrost in large parts of the calcareous mountains.

Scientific Collaboration on Past Speciation Conditions in Lake Ohrid—SCOPSCO Workshop Report

Scientific Collaboration on Past Speciation Conditions in Lake Ohrid—SCOPSCO Workshop Report

Biodiversity of Macrophyte Vegetation from Lake Prespa, Lake Ohrid and Lake Skadar

ABSTRACTLake Prespa, Lake Ohrid and Lake Skadar are the biggest lakes in the Balkan Peninsula. By reason of continuous existence and relatively stable ecological conditions millions years those lakes have a unique collection of flora and fauna.In this paper is presented biodiversity of macrophyte vegetation from Lake Prespa, Lake Ohrid and Lake Skadar. In those three lakes macrophyte vegetation is distributed in zones (belts). The biodiversity of macrophytes is different in those lakes and it is in direct dependence of different altitudes, lakes surfaces and lakes depths.

Biodiversity of Ichthyofauna from Lake Prespa, Lake Ohrid and Lake Skadar

ABSTRACTLake Prespa, Lake Ohrid, and Lake Skadar are the biggest lakes in the Balkan Peninsula.In this paper are presented the researches of the fish populations qualitative composition in Lake Prespa, Lake Ohrid and Lake Skadar. In those three lakes as result of negative anthropogenic impact there are changes in fish biodiversity (with more presence of alochtonous species). In this way, unfortunately autochthones populations of fishes (which are rich by endemic and relict species) are endangered.By reason of inserting news species, the fish populations are endangered, especially the populations of particular zoographically significant species. So, it is necessary to proceed the procedure to their inserting in the Red list of endangered species.The abundance of the fish populations in the three biggest lakes in the Balkan Peninsula is in dependence from of their different altitudes, surfaces and depths. Also, the qualitative composition of the fish populations in those lakes depend from the different physic-chemical conditions, biological communities (phytoplankton, zooplankton, bottom fauna), and especially from the macrophyte vegetation.

Monogenean Trematods—Parasites of Some Cyprinid Fishes from Lakes Ohrid and Prespa (Macedonia)

ABSTRACTDuring parasitological investigations of the gills of 3 cyprinid species from lakes from the Adriatic river basin of Macedonia (Lake Ohrid and Lake Prespa), 7 monogenean species were found: in Chondrostoma nasus we found: Dactylogyrus elegantis, D. vistulae and Paradiplozoon homoion homoion, in Alburnus alburnus we found Dactylogyrus alatus f. typica, Dactylogyrus minor, Diplozoon paradoxum and Paradiplozoon alburni, in Alburnoides bipunctatus we found Dactylogyrus alatus f. typica and Paradiplozoon alburni. Prevalence in Chondrostoma nasus ohridanus is 50,0%, in Chondrostoma nasus prespensis is 41,59% (in total Chondrostoma nasus - 41,88%), in Alburnus alburnus ohridanus is 47,75%, in Alburnus alburnus prespensis is 41,38% % (in total Alburnus alburnus - 44,95%), in Alburnoides bipunctatus ohridanus is 35,14%), in Alburnoides bipunctatus prespensis is 11,54% (in total Alburnoides bipunctatus - 29,0%). The most frequent monogeneans found in the fishes from both lakes are: Dactylogyrus alatus f. typica (established in 17,62% of all examined fishes) and Dactylogyrus minor (established in 16,31% of all fishes). Dactylogyrus alatus f. typica, D. minor, Diplozoon paradoxum and Paradiplozoon alburni represents a first record for the parasite fauna of fishes in Macedonia. The greatest pathological influence is associated with the monogeneans: Dactylogyrus vistulae, Paradiplozoon homoion homoion, Paradiplozoon alburn and Diplozoon paradoxum.