Lake Mikri Prespa Research Articles

The Breeding colonies, population growth and breeding success of the Dalmatian pelican Pelecanus crispus in Greece: a country-wide perspective, 1967-2021

Greece holds the third larger breeding population of Dalmatian Pelican in the world. We present data about the establishment and growth, breeding performance and conservation status for all six colonies of the species in Greece for 40 years. Main features of wetlands and colonies are described. We discuss the local, regional and global natural and anthropogenic factors that may have affected colony growth. After 1982 colony surveys were carried out with various methods, adapted to the particularities of each wetland and availability of resources, and targeted estimating number of nests and number of near-fledged young via direct counting either during on-site visits or from vantage points, and recently, counts on photos taken by drones flown one or more times during breeding. Number of nests in Lake Mikri Prespa rose from ca. 100 to 1200-1500 and levelled-off. DPs from Prespa started breeding successfully in Kerkini in 2004 after placement of artificial nesting rafts. The Karla Reservoir was colonised in 2011, just two years after it started filling with water. The DP colony on Lake Chimaditis, an important stop over and feeding site, probably initiated around 2016 and continues growing. The two colonies at the western coastline have limited exchanges with those in the eastern part of the country. Amvrakikos increased and levelled off recently as conservation and management measures restricted disturbance, whilst emigrants re-established the old colony at Messolonghi in 2011 which continues to grow. The overall breeding population in Greece grew from ca 100 to over 2000 br pairs showing an annual growth rate of 7.9%. Younger colonies show high annual growth rates clearly attributed to immigration, while older colonies have growth rates less than 10%. Interacting natural and anthropogenic factors are assumed to have contributed to pelican increase in Greece the last 40 years: better legal protection status, increasingly effective protection, patrolling and conservation measures; public awareness campaigns; provision of artificial nesting structures; increased winter survival due to higher temperatures owed to climate change; less disturbance and persecution due to decline of fisheries; increasing abundance and availability of fish due to eutrophication and climate change; increasing numbers of sympatric great cormorants rendering pelican fishing more efficient; appearance of new wetlands and change of wetlands due to human intervention works.

Seasonal Shifts in Soil Microbiome Structure Are Associated with the Cultivation of the Local Runner Bean Variety around the Lake Mikri Prespa.

Leguminous crops play a key role in food production and agroecosystem sustainability. However, climate change and agricultural intensification have a significant impact on the available arable land, soil microbiome functions, and ultimately, crop productivity. The "Prespa bean" (Phaseolous coccineous L.) is an important leguminous crop for the agricultural economy of the rural areas surrounding the lake, Mikri Prespa, which is of significant ecological importance. The seasonal effects on soil microbiome structure, diversity and functions associated with the runner bean cultivation were investigated using 16S rRNA amplicon sequencing. The results indicated that the presence of the runner bean differentially shaped the soil microbial community structure. The runner bean was implicated in the recruitment of specific bacteria, by favouring or excluding specific classes or even phyla. Soil functions involved in nutrient availability and carbon metabolism, among other pathways, were associated with microbiome-plant interactions. The temporal relative abundance shifts could be explained by the impact of soil organic matter, the fertilization regime, and the equilibrium in carbon metabolic processes. This research has shown the effect of runner bean cultivation on the soil microbiome which, in future, may potentially contribute to research into sustainable agricultural productivity and the protection of soil ecosystem services.

NUTRITIVE VALUE OF RIPARIAN COMMON REED BIOMASS FOR RUMINANTS

The extensive reedbeds, especially Phragmites australis, that spread around then perimeter of the lake Mikri Prespa, a Ramsar protected lake in the northwest of Greece, serves beneficially for several human activities and wildlife needs. Nevertheless, the apparent overgrowth and removal of this vegetation is often problematic and imposes difficulties in management and increases costs. Recent research is focusing into the use of P. australis as an alternative or complementary feed for ruminants. The aim of the present study was to evaluate the nutritive value of P. australis biomass derived from the riparian vegetation as a potential animal feed. Biomass samples were collected from six different sites of the Mikri Prespa lake in two different time periods (i.e. early August and late October 2020). The samples were analyzed for macro- and trace elements, total protein, NDF, fat and nitrogen-free extracts. Location and sampling date had a significant effect on all macronutrient concentrations with significant reductions in the second sampling period. For the trace elements zinc, copper and boron higher concentrations were observed in August, while the concentration of iron increased significantly in October. Dry matter and NDF content of P. australis was particularly high, 67.08% and 46.3% respectively; while protein content was rather moderate (8.38%, August sampling) to low (5.06%, October sampling). The results show that the nutritive value of P. australis is comparable to feeds widely used in ruminant nutrition such as wheat straw or marc, indicating a potential use as an alternative or complementary coarse feed with appropriate administration or treatment.

Ridge-and-Furrow Agriculture around Lake Mikri Prespa, Greece, in a European perspective

Ridge and furrow is an archaeological pattern of ridges and troughs used in Europe, frequently associated with communal open-field farming and strip cultivation. Strip farming spread throughout Europe in the Middle Ages but appears to have only slightly penetrated southern Europe. In Greece, no areas under a ridge-and-furrow system were previously known. Working on 1945 aerial photos of Prespa, Greece, a border area around two lakes whose water levels fluctuate seasonally, we noted the presence of strip fields around the lakeshore, and subsequently identified them in the field as a ridge-and-furrow system. Using GIS, we measured the dimensions of all individual fields and collected oral histories from elderly locals. The area under strip farming was over 900 ha. Strips were straight, ca 200 m long and 10m wide, with a mean area of 2,160 m2. Wheat, rye, maize and beans were cultivated on the ridges, whilst grass in the furrows was mowed for hay. The construction and dimensions were almost identical to those seen in England. No information was found on either the origin of this system in Prespa, or connections with ‘zadruga’ or ‘chiftlik’ – other regional communal land management systems. A few adjacent areas with strip cultivations still in use were located in the two neighbouring countries sharing the lakes, and still fewer areas with ridge-and-furrow traces, particularly around lakes. By using ridge-and-furrow agriculture, local people had successfully coped with the perennial and seasonal inundation of their fields, a problem that remains unresolved and afflicts modern biodiversity conservation in the area.

Temporal trends and determinants of fish biomass in two contrasting natural lake systems: insights from a spring long-term monitoring scheme

Freshwater fish declines are triggered by a suite of anthropogenic threats, including habitat degradation, climate and land use change, biological invasions, pollution and overfishing. Robust monitoring schemes are needed to understand and detect any effects of different factors on freshwater fish abundance and to be able to predict and respond to potential stressors. Here, we used standardized biomass-per-unit-effort (BPUE) data deriving from gillnet sampling over a 34-year period in the two Prespa Lakes and determined species trends using general additive models coupled with structural change models. Furthermore, the influence of seven environmental variables was assessed for each fish species using an analytical approach based on random forests. We showed that the total annual BPUE is increasing in Lake Mikri Prespa whereas it is stable in Megali Prespa and that the relative BPUE of introduced species in the former is increasing through the years. Differences in the lakes' trophic status were reflected in species trend patterns. Random forests showed that air temperature, the introduction of the invasiveLepomis gibbosus, predation and water management played a role in shaping species biomass in Mikri Prespa whereas abiotic factors are the main drivers of biomass changes in Megali Prespa. Our results provide empirical evidence on the importance of long-term monitoring in distinguishing between direct and indirect effects of large-scale stressors on fish abundance as well as insights towards sustaining the integrity of fish communities.

Ecological Connectivity in Two Ancient Lakes: Impact Upon Planktonic Cyanobacteria and Water Quality

The ancient lakes Mikri Prespa and Megali Prespa are located in SE Europe at the transnational triangle and are globally recognized for their ecological significance. They host hundreds of flora and fauna species, and numerous types of habitat of conservational interest. They also provide a variety of ecosystem services. Over the last few decades, the two lakes have been interconnected through a surface water channel. In an attempt to explore whether such a management practice might alter the ecological properties of the two lakes, we investigated a series of community metrics for phytoplankton by emphasizing cyanobacteria. Our results demonstrate that the cyanobacterial metacommunity structure was affected by directional hydrological connectivity and high dispersal rates, and to a lesser extent, by cyanobacterial species sorting. Cyanobacterial alpha diversity was twofold in the shallow upstream Lake Mikri Prespa (Simpson index average value: 0.70) in comparison to downstream Lake Megali Prespa (Simpson index average value: 0.37). The cyanobacterial assemblage of the latter was only a strict subset of that in Mikri Prespa. Similarly, beta diversity components clearly showed a homogenization of cyanobacteria, supporting the hypothesis that water flow enhances fluvial translocation of potentially toxic and bloom-forming cyanobacteria. Degrading of the water quality in the Lake Megali Prespa in anticipation of improving that of the Lake Mikri Prespa is an issue of great concern for the Prespa lakes’ protection and conservation.

Cyanobacterial Toxic and Bioactive Peptides in Freshwater Bodies of Greece: Concentrations, Occurrence Patterns, and Implications for Human Health.

Cyanobacterial harmful algal blooms represent one of the most conspicuous waterborne microbial hazards in aquatic environments mostly due to the production of toxic secondary metabolites, mainly microcystins (MCs). Other bioactive peptides are frequently found in cyanobacterial blooms, yet their concentration and ecological relevance is still unknown. In this paper we studied the presence and concentration of cyanobacterial peptides (microcystins, anabaenopeptins, anabaenopeptilides) in 36 Greek freshwater bodies, using HPLC-DAD, ELISA, and PP1IA. Microcystins were found in more than 90% of the samples investigated, indicating that microcystin-producing strains seem to also occur in lakes without blooms. Microcystins MC-RR, MC-LR, and MC-YR were the main toxin constituents of the bloom samples. Anabaenopeptin A and B were predominant in some samples, whereas anabaenopeptolide 90A was the only peptide found in Lake Mikri Prespa. The intracellular concentrations of anabaenopeptins produced by cyanobacterial bloom populations are determined for the first time in this study; the high (>1000 µg·L−1) anabaenopeptin concentration found indicates there may be some impacts, at least on the ecology and the food web structure of the aquatic ecosystems. The maximum intracellular MC values measured in Lakes Kastoria and Pamvotis, exceeding 10,000 µg·L−1, are among the highest reported.

Mollusc biodiversity in a European ancient lake system: lakes Prespa and Mikri Prespa in the Balkans

The spatial distribution of (endemic) biodiversity in ancient and potentially ancient lakes in Europe is poorly understood. Examples include Lakes Prespa and Mikri Prespa in the Central Balkans. Utilizing information of the most species-rich taxon in these lakes, the Mollusca, we therefore attempt to statistically assess and visualize the spatial distribution of biodiversity, to analyse biogeographical patterns, and to carry out a conservation assessment. We estimate that at least 40 (sub)species (29 gastropod and 11 bivalve taxa) occur in the lakes. For both lakes combined, 37.5% of the mollusc taxa are endemic. In general, the mollusc richness in Lake Mikri Prespa is lower than in Lake Prespa and less heterogeneously distributed. The highest species richness can be seen on the western and south eastern shores of Lake Prespa. Based on the presence/absence of genera, a minimum spanning tree analysis supports the sister lake relationship of both lakes, which, in turn, are most closely related to lakes in the western Balkans and not to nearby Lake Ohrid. The IUCN red list assessment revealed (A) a tendency towards mollusc faunal change, (B) a contemporary decline and potential loss of mollusc diversity, and (C) that all endemic species are of conservation concern.

Habitat and Temporal Variation in Diet of Great Cormorant Nestlings in Greek Colonies

Abstract Diet of Great Cormorant (Phalacrocorax carbo sinensis) nestlings was studied during four consecutive breeding seasons (1999-2002) at three Greek colonies (Axios Delta, and Lakes Kerkini and Mikri Prespa) in order to assess variation and commercial value of prey. A variety of fish taxa were found in nestlings’ regurgitates in each area and season, but only one or two dominated by numbers or biomass. Black Goby (Gobius jozo), Round Sardinella (Sardinella aurita) and Twaite Shad (Alosa fallax) were the most important prey in the Axios Delta; Bleak (Alburnus alburnus), Giebel (Carassius auratus gibelio) and Roach (Rutilus rutilus) at Lake Kerkini; Chalcalburnus belvica and Giebel at Lake Mikri Prespa. Nestling diet varied both seasonally (but only at Lake Kerkini significantly so) and annually (significantly in the Axios Delta and at Lake Mikri Prespa). Temporal changes can be attributed to changes in prey availability and abundance and confirm this bird’s opportunistic behavior. Between-colonies, di...

Reproductive performance of the great cormorant (Phalacrocorax carbo sinensis) in three Greek colonies

Several breeding parameters of the great cormorant (Phalacrocorax carbo sinensis) were studied in Greece in 2001 and 2002 and were found to be generally higher at Lake Kerkini than in the other colonies. Fledging success (proportion of hatched eggs that led to fledged nestlings) was significantly higher at Lake Kerkini and in the Axios Delta in both years than at Lake Mikri Prespa in 2002. Mean fledgling production (the number of young fledged per initiated clutch) was significantly higher at Lake Kerkini than at Lake Mikri Prespa in 2002. The high fledgling production (2.15–2.75 fledglings on average in this study), the high food availability and the low initial population density allowed the total Greek breeding population to grow at a fast rate (19.0% per annum) in the 1990s. Given the scarcity of information on great cormorant nesting in Greece, basic breeding parameters are important for modelling population dynamics.

Nesting Habitat Characteristics and Breeding Performance of Dalmatian Pelicans in Lake Mikri Prespa, NW Greece

-Dalmatian Pelicans (Pelecanus crispus) in Lake Mikri Prespa nest on islands of Common Reed (Phragmites) rhizomes formed at the interface between marsh and open water and mostly ranging from 6-80 m2 in area. Nest density from 1984 to 1996 varied from 0.12 to 1.2 nests/m2. Large islands were not more densely occupied than smaller ones. Higher nest densities were observed in the second and third year that a site was used. Islands used for nesting were degraded by weather, water and use by the birds and shrank in size by 1-55% each year; thus some were abandoned and new ones colonized each year. On the average, sites were used for three years in succession, but initially larger sites were used much longer. Nest site quality was related to island rigidity and the availability of nesting material on it. Numbers of breeding pelicans at Prespa are probably limited by the availability of suitable nest sites and, especially, larger islands, since breeding success is positively correlated with the mean nesting assemblage size (number of breeding attempts/number of sites). Artificial nesting rafts are likely to be more successful the more their features comply with the above findings and the more they enhance overall colony compactness. Received 15 April 2001, accepted 18 August 2001.

Organochlorine compounds in pelicans (Pelecanus crispus and Pelecanus onocrotalus) nesting at Lake Mikri Prespa, north western Greece.

Organochlorine compounds in pelicans (Pelecanus crispus and Pelecanus onocrotalus) nesting at Lake Mikri Prespa, north western Greece.

The breeding biology of the Dalmatian Pelican Pelecanus crispus

The breeding biology of the Dalmatian Pelican Pelecanus crispus, a vulnerable bird species in the Palaearctic, has been studied for 7 years at Lake Mikri Prespa, a continental wetland and Tsoukalio lagoon, a coastal wetland within the Amvrakikos Gulf. The two colonies showed stability, with fluctuations in the number of breeding attempts each year varying by about 30% over a period of 7 years. The date of arrival at the breeding sites and the date of laying of the first egg varied between mid‐February and mid‐March. The egglaying period (including renesting) varied between 18 and 114 days between years. The annual average clutch size varied between 1.60 and 1.94 eggs per nest. The incubation period averaged 31.4 ± 1.4 days. The overall hatching success varied from 36% to 70%. Egg losses were mainly due to nest abandonment, infertile eggs and eggs rolled from the nests. The Dalmatian Pelican chicks took 11–12 weeks to fledge. Nestling mortality was very low in contrast to other species of pelican. Such a low nestling mortality explains why the breeding success each year is largely explained by the hatching success.

Planktic cyanophytes and their ecology in the shallow Lake Mikri Prespa, Greece

Cyanophytes dominated the phytoplankton of shallow Lake Mikri Prespa during the period May 1990 to September 1992 (76.5 and 52.0% of the total phytoplankton biomass in 1990–1991 and 1991–1992, respectively). Biomass peaks were observed in autumn (from 5.2 to 34.5 g m‐3) when low dissolved inorganic nitrogen, high phosphate phosphorus and low Zcu to Zmix ratio prevailed. The dominant species were Microcystis aeruginosa and M. wesenbergii. These represented 64 and 86% of the cyanophyte biomass in 1990–1991 and 1991–1992, respectively and revealed similar patterns of seasonality forming biomass peaks in late summer ‐ autumn. Small chroococcalean cyanophytes (< 2 μm) showed also similar temporal distributions. Of the filamentous cyanophytes, the most important species was Anabaena lemmermannii var. minor which formed peaks in late summer and autumn (2.6 and 1.1 g m‐3 in 1990 and 1992, respectively). Rainfall and the N:P ratio were probably the main factors influencing the seasonality of all of the filamentous cyanophytes in the lake. Cyanophytes, tended to increase at temperatures higher than 16 °C and at inorganic nitrogen concentrations lower than 100 μg 1‐‐1. The frequent mixing of the water column did not seem to prohibit the substantial increase of the group.

Species composition and seasonal cycles of phytoplankton with special reference to the nanoplankton of Lake Mikri Prespa

The phytoplankton of Lake Mikri Prespa was studied atmonthly or biweekly intervals during the period May1990–September 1992. Its species composition,consisting of a great number of cyanophytes and a verysmall number of chrysophytes and desmids, may reflectthe eutrophic character of the lake. Moreover, themean annual biomass values (15.0 and 3.2 g m−3 inthe two years, respectively) and the maximum biomass(38.1, 6.4 and 9.6 g m−3), classify Mikri Prespaas a eutrophic lake. A tendency towards adouble-peaked pattern of biomass distribution in timewith one peak in autumn, composed mainly ofcyanophytes, and another in spring made up of diatoms,was observed. This pattern contrasts with the standardpattern in eutrophic, stratified temperate lakes,which exhibit a third biomass maximum in summer. Cyanophytes were the most important group in terms ofbiomass and were dominated by the species Microcystis aeruginosa, Microcystis wesenbergii,Anabaena lemmermannii var. minor and Aphanocapsa elachista var. conferta. Diatomsconstituted the second most important group, with main representative the species Cyclotellaocellata. Cyanophytes, diatoms, chlorophytes anddinophytes revealed annual periodicity whereas theother algal groups did not show any seasonality atall. The nanoplankton constituted an important part ofalgal biomass (38.9 and 49.9% in the two years,respectively) and revealed annual periodicity withmaximum values in winter and spring, mainly composedof diatoms and cryptophytes. Low temperature,increased rainfall and high DIN concentrations seemedto be the main factors influencing the seasonality.Although the percentage contribution of nanoplanktondecreased with the increase in total biomass,justifying the classification of Lake Mikri Prespaamong the eutrophic lakes, the nanoplankton biomassdid not correlate significantly with totalphytoplankton biomass.

The Effects of the 1989/1990 Drought on the Colonial Waterbirds Nesting at Lake Mikri Prespa, Greece, with Special Emphasis on Pelicans

The Effects of the 1989/1990 Drought on the Colonial Waterbirds Nesting at Lake Mikri Prespa, Greece, with Special Emphasis on Pelicans

Feeding Ecology of the Great White Pelican (Pelecanus onocrotalus) Nesting at Lake Mikri Prespa (Northwestern Greece)

Feeding Ecology of the Great White Pelican (Pelecanus onocrotalus) Nesting at Lake Mikri Prespa (Northwestern Greece)

An economic assessment of an irrigation project affecting a Greek wetland

The marshes and wet meadows surrounding Lake Mikri Prespa, Greece, are internationally significant wetlands scheduled in the Ramsar Convention. This environment was adversely affected in the 1960s by an irrigation project and the associated drainage and roads intended to increase agricultural production and income. The anticipated project construction phase was scheduled to take two years, but took two decades. The public cost of the project was 4.4 times the initial estimate, while the irrigated area is only 41.3 percent of that planned. The adverse environmental impacts included a reduction in wetland area and the negative effects of intensive farming. An ex-post cost-benefit analysis shows that the social value of the project is negative, so that the economic losses would have been avoided by conserving the area in its natural state, quite apart from its intrinsic environmental value. However, the benefits to farmers, although less than that expected, were substantial, thus explaining the local support for the further expansion of irrigation.

Benthos of Lake Mikri Prespa (North Greece)

An extensive sampling of Lake Mikri Prespa was carried out in summer 1990, aimed at evaluating benthic abundance, recording the species involved and detecting their response to some environmental variables. Three oligochaete species are endemic to the region,Potamothrix prespaensis, Psammoryctides ochridanus variabilis andPsammoryctides ochridanus typica. The bathymetric curve of the benthos resembles that of eutrophic lakes. A great abundance ofChironomus plumosus andChaoborus flavicans occurred. Four community patterns were revealed by TWINSPAN analysis, division level two, explicitly discriminated by the influence of substrate type, depth, C/N ratio and pH. Species richness and diversity was minimal in the profundal and maximal in the shallows, whilst the equitability index was high in all site groups. Depth and bottom type were the most important variables in defining species distribution. More precisely,Chironomus plumosus, Chaoborus flavicans andPotamothix hammoniensis were ubiquitous, preferring mostly deep waters.Tanytarsus sp.,Einfeldia dissidens, Cladopelma lateralis, Tanypus punctipennis andPotamothrix prespaensis favoured shallower and less productive waters with a bottom rich in decaying plant fragments, and thePsammoryctides species showed a littoral origin and regular occurrence on gravel beds. A few species displayed a particular distribution with changes of depth, C/N ratio and pH.

Are fish introductions a threat to endemic freshwater fishes in the northern Mediterranean region?

Seventy species of exotic or transplanted fish species have been introduced into this region, 60% of them in the last 40 years. The effects of these introductions on endemic species have rarely been described. The few exceptions are: hybridization of Salmo marmoratus with Salmo trutta; the extinction of three endemic species of Phoxinellus in a Turkish lake owing to the introduction of Stizostedion lucioperca; and the spatial displacement of Aphanius in sites where Gambusia affinis occurs. A further phenomenon possibly attributable to the introduction of exotic fish is the increased turbidity in Lake Mikri Prespa following the introduction of Carassius auratus. Because of the paucity of information, the effects of introductions on endemic species remain controversial. It is therefore essential to initiate conservation action plans, for each catchment in wetland areas rich in endemic fish. An awareness campaign directed at land managers and decision-makers on the role and importance of fish in the functioning of aquatic ecosystems must also be undertaken very soon.