|
Lake Wigry - the lake "adopted" by International Association of Theoretical and Applied Limnology The Conservation Committee of International Association for Limnology (Societas Internationalis Limnologiae - SIL) has accepted Lake Wigry, within the Wigry National Park, as a first lake to be adopted by SIL. This decision was made during the XXVII SIL Congress in Dublin, 8-14 August 1998. Lake Wigry meets well the criteria for adoption set out by the Conservation Committee. These criteria are:
Lake Wigry and it's surroundings Lake Wigry and 41 other lakes in Wigry National Park are located in north-eastern Poland close to the Lithuanian border. The landscape of the area was shaped during the Baltic phase of the last glaciation, which reached here its maximum point about 15,000 years ago. The retreat of the glacier left water reservoirs - the elongated ribbon lakes, irregular in shape marginal lakes and rounded in shape thaw lakes, of the very diversified morphometry. In the water catchment of Lake Wigry there is Lake Hancza - the deepest lowland lake of Central Europe (depth 108 m). Despite its common geological past, the lakes of this region represent today different stages of succession in the direction of eutrophy or dystrophy (polyhumic lakes). In the area of the park there are lakes which range from oligo-mezo to advanced eutrophy. The majority of the lakes are mezo-eutrophic water bodies with calcium rich water. In the forests there are brown water, polyhumic lakes with water showing different levels of natural acidification - from very acidic (pH ca 4.0) to almost neutral. Besides the lakes there are rivers, streams, springs, and different types of wetlands. The unique variety and diversity of the habitats in the small area (150 km2) have on the European scale a high value for nature and the area's attractiveness for limnological research.
Lake Wigry is an unusual, mesotrophic lake. It consists of a few basins connected by straights which together with bays and islands divide water masses into several water regions. Each region of the lake has its own unique water depth. The shape of the lake and the lake bottom is conducive to diverse habitat conditions, in particular in trophy, thermal and oxygen conditions, and water exchange. It gives an opportunity to conduct research on the response of the species and communities to the spatial diversification of habitat conditions within one lake. The littoral of Lake Wigry is also diversified with short and long longshore bars. About 90% of the shoreline up to depth to about 1.5 m. is covered by emergent macrophytes. The dominating species are reed (Phragmites australis), reedmace (Typha angustifolia), bulrush (Schoenoplectus lacustris), and different sedges (Carex sp., Cladium mariscus). The width of the reed beds varies but usually ranges from 10 - 20 m. There are submerged plant communities in depths to 4.5 m., which cover about 13% of the lake's surface area. The species composition, biomass, and distribution of submerged macrophytes vary. Ceratophyllum demersum, Potamogeton perfoliatus, P. lucens, P.compressus, Batrachium circinatum, Fontinalis antypyretica and Chara sp dominate. Due to the reduction in water transparency some photophilous species are decreasing in number (eg. Chara sp.) while species tolerant to shade are increasing (e.g. Ceratophyllum, Fontinalis). Additionally, in some time periods in the littoral the filamentous algae (Mougeotia sp., Spirogyra sp., Stigeoclonium sp.) appeared. These algae also live below the macrophyte range. On the surface of water plants in Lake Wigry and other hard water lakes calcareous encrustations are observed. The intensity of biological decalcification of water and the role of this process in phosphorous circulation and eutrophication of the lake are unknown and require investigation. There is little known about the present species richness of the littoral macrofauna. Preliminary investigations on molluscs show the presence on this area 13 taxons of snails, 6 species of big mussels and an unknown number of species from the family Sphaeridae. In biomass the dominating species is the zebra mussel (Dreissena polymorpha). An interestingly but not sufficiently investigated invasive species of snails, Potamopyrgus antipodarum, show a large fluctuation in number. The bottom of the littoral of Lake Wigry covers sediments of diversified character. In some parts of the lake there are calcerous gyttja sediments while in other parts there are gravel, sandy, muddy or organic sediments. In the shallow water sediments and sandy beaches of Lake Wigry, J. Wiszniewski discovered in the 1920's and 1930's a community of psammon rotifers. Wiszniewski presented the results to three congresses of SIL (Amsterdam - 1932, Belgrade - 1934 and Paris - 1937). Three new genera of rotifers (Wigrella, Wierzejskiella and Myersina) and 14 new species from the other genera of rotifers were discovered. Unfortunately, nobody continued Wiszniewski's work on psammon communities. In the sublittoral, the chalky sediments frequently border the sediments having typically profundal characteristics. The response of benthic communities is unknown about such a patched distribution of sediments. Also, the benthos of the deepest places of Lake Wigry and the deeper Lake Hancza is poorly known despite the old records of the occurrence in this lake rare and relic species of crustaceans, Mysis relicta, Pallasea quadrispinosa and Pantoporeia affinis. On the shore of Lake Wigry and other lakes and rivers of the park, there is a large population of beavers (Castor fiber) saved in Poland by species protection, habitat protection, and active restitution. At present, more than 350 beavers that inhabit the park are changing the course and the water levels in small rivers and influence the structure of the shore vegetation. We can assume that the beaver population reached its maximum number. The biocenotic role of these biggest European rodents as well as beaver's ecology in overpopulated conditions is not sufficiently investigated. In ichtyofauna 32 species have been recorded. The first credible information on fish is from 1569 showing "salmon" (probably lake brown trout Salmo trutta m. lacustris), European white fish (Coregonus lavaretus), white fish (Coregonus albula), pike (Esox lucius), bream (Abramis brama), crucian carp (Carassius carassius), perch (Perca fluviatilis) and other species which occur in Lake Wigry. We can assume from the results of fish catches in the 19th century that the population of the autochtonous European white fish was surely not numerous. From the beginning of the 20th century until the end of the 1920's, the numbers of fish from the family Coregonidae dramatically dropped and were caught only occasionally. The construction of a fish hatchery in 1928 and the intensive fish stocking led to the enlargement of both the white fish and European white fish. At present, white fish is the dominating species in Lake Wigry. During the last 100 years, the composition of ichtyofauna distinctly changed because of the fishery management as well as the rising trophy of the lake. Significant is the process of decreasing share of smelt in fishery catches from 50% in the 1920's to about 15% in the mid-1970's and less than 1% at present. The park has conducted the active protection of ichtyofauna since 1994.The main direction of the protection methods are: to increase the number of predatory fish through fish stocking and prohibiting the catch of predatory fish, to reduce the number of cyprinid fish through catches and biomanipulation (increase number of predatory fish), to upkeep the present species diversity, and to restore species which became extinct (brown lake trout) or to enlarge the number of the threatened species (wels Silurus glanis). The park, which has its own fish hatchery and fisherman, can radically change the species composition and the number of fish to reach the best effects through the full protection of Lake Wigry's ecosystem. Monitoring of such large-scale biomanipulation can become a fascinating subject for scientific studies. The study of the relationship between numerous pelagic fish and zooplankton can be of great importance for understanding the ecosystem structure and functions. In particular regions of the lake the zooplankton composition is not homogeneous. To some extent, the different rate of eutrophication of these water regions can explain this phenomenon. Generally, pelagic zooplankton of Lake Wigry are average in number but are rich in species. During the summer, up to 27 species of rotifers and up to 22 species of crustaceans were recorded.
The composition of the zooplankton indicates the low trophy of the lake. In the summer at the majority of the stations the Daphnia cucullata dominates in zooplankton biomass. High species diversity of the pelagic zooplankton gives a very specific value to the lake particularly by the occurrence of relic and rare species of crustaceans like Daphnia longiremis, Eurytemora lacustris, Heterocope appendiculata and Holopedium gibberum. Lake Wigry features a large variety of Cladocera and the occurrence of many genera from this group and co-occurrence of many species of the same genus. In particular it deals with genus Daphnia, where at one station 3-5 taxa (species or subspecies) were found. Until now there were not elucidated mechanisms of niches segregation (habitat and food) of the large zooplankton species and its impact on minute zooplankton as well as the avoidance of the fish predation. It will be interesting to understand the cascade effect of such a composition of a fish community in which species that feed on zooplankton dominate and large zooplankton species commonly occur. There are unknown mechanisms that support this co-existence of predators and their prey that can provide an interesting subject for research. Threats to the aquatic ecosystems The basic threat to the water ecosystem of the park, including Lake Wigry, is eutrophication. Three years ago almost 80% of the nutrients in Lake Wigry were brought by the river Czarna Hańcza which serves as the sewage receiver from the nearby city of Suwałki (population 70,000). It also collects pollution from the catchment of the area of 170 km2. In 1985, the sewage water treatment plant was constructed and was able to manage 95% of the organic waste. But, still, the annual load with phosphorus from the catchment area was 0,68 g P*m-2 which was 4.4 times higher than the specified Vollenveider's criteria. Since 1997, the water quality radically improved due to the modernised technology of biological treatment and the introduction of chemical precipitation of surplus phosphorus compounds. The phosphorus concentration dropped ca. 40% and slowed the process of lake eutrophication. Although there is a decrease in phosphorus concentration, the transport of nutrients and other pollution by the river Czarna Hańcza still presents a threat to the lake.Other types of pollution include municipal sewage, which originates in households located in the direct water catchment, frequently on the shore of the lake. The majority of the villages around Lake Wigry lack a sewage water collection system, and seepage of the sewage to the ground and surface water occurs. It is evident from the microbiological analysis of the open water and wells. The Director of the park has been working to mobilise the local authorities to construct a local sewage treatment plant, but the process is very long, difficult, and costly. The other sources of nutrients are of lesser importance, but, of course, shouldn't be ignored. Agricultural impact is low because of the small amount of arable land in the direct catchment (18%) and its extensive character. The park is protected against intensification of agriculture by legal regulations, which prohibit the development of mass animal production, use of manure in the fields, and pesticide and fertiliser distribution, by aeroplane. Activity of the Hydrobiological Station at the Lake Wigry Intensive investigation of Lake Wigry and the other water areas in the Suwałki region started in 1920 by setting up of the Hydrobiological Station. The research activity of the Station, managed by Dr Alfred Lityński, contributed greatly to the European limnology until 1939. Even now, the range, complexity, and intensity of the research conducted continue to be impressive. The scientific workers of the Station and its visitors published about 100 research papers on hydrography, hydrochemistry, phytoplankton, zooplankton, bottom fauna, vegetation, fish and other groups of water organisms of Lake Wigry. In more than 200 other papers there are records on Lake Wigry. At this time the unique nature value of Lake Wigry and surrounding waters were documented. It includes information about relic, endemic and rare animal species and it initiated the development and implementation of its protective status as a nature reserve. The published scientific information allows today comparable studies to be conducted. The Hydrobiological Station played a very important role as a school of limnology and as a working place for visiting scientists, including prominent foreign limnologists. The guests of the Station among others were A.Thienemann, P.I.Eglit, B.Hayneman, E.Naumann, B.Schröder and J. Zavrel. In the summers the Station provided limnological courses for students who would later become famous Polish limnologists. Today, the Station is known as the 'cradle' of Polish hydrobiology. Dr Alfred Litynski brought great input into the development of limnology. In 1921, world famous limnologists Einar Naumann and August Thienemann invited him to work for the preparation of the first International Limnological Congress which took place in 1922 in Kiel. Dr Lityński played an active part in Societas Internationalis Theoreticae et Applicatae Limnologiae and worked in organisation committees of the next Congresses in Innsbruck and Rome. In the Stockholm Congress, he received a medal Pro limnologia optime merito for his scientific achievements. One of the very important works of Lityński, besides the original hydrobiological papers, was the writing of the first Polish limnology handbook. He started the publication of the first hydrobiological periodicals of which the longest surviving periodical is the "Archives of Hydrobiology and Fisheries" from 1926 - 1939 and then called "Polish Archives of Hydrobiology" after World War II. The outbreak of World War II halted the activity at the Hydrobiological Station and its work has never been resumed. The death of top limnologists among others, Lityński, Wiszniewski and Z. Koźmiński, destruction of laboratory and field equipment, and the shift of importance to the Mazurian Lakeland resulted in the inability to restart the work at the Station. The building of the former Station became the property of Wigry National Park, and will be turned into a museum for the park's water ecosystems and past activity of the Hydrobiological Station. Organisation and conditions of scientific work at Lake Wigry Wigry National Park has its own scientific department, which carries on investigations and co-operates with many scientists and scientific institutions. The park possesses means of transportation (cars, boats), tools for fish catches, precise sonic meter with recorder of echograms, GPS receivers, microscopes, multiparameter probes, field spectrophotometer, dryer, and other laboratory equipment. Data is collected and entered into specific computer programs (databases, GIS applications). The park's laboratory provides physical and chemical water analysis and biological sample analysis. Guestrooms are available in the park's headquarters, and groups of scientists can find lodging in the Scientific & Education Centre located directly on the shore of Lake Wigry. The research department has its own library, but also has access to professional literature due to co-operation with the library of the Institute of Ecology in Dziekanów Leśny which contains ecological and limnological periodicals, including an archive. It is essential that for some kind of research (i.e. water chemistry or zooplankton) there are historical data from a few periods, started in the 1920's and 1930's. It gives them the opportunity for interesting comparable studies. The water research is only a part of the duties of the research department and is related mainly with the monitoring observations and measurements. At present the Park co-operates with the following scientific institutions regarding water research:
Co-operation with these scientific centres contributes to knowledge of chosen groups of organisms or chosen processes. The increase in scientists and research is necessary to conduct investigations in order to combine and understand the most important natural processes within the lakes' ecosystem. A long-term research program is being prepared in which the results will be utilised in the development of a future management plan for the park. Co-operation with SIL - implementation of the Lake Adoption Project The "adoption" program, proposed by the Conservation Committee, comprises several activities:
Such co-operation with SIL could provide the stimulus to revive the limnological research on the Lake Wigry complex and help in preservation of it's unique, nature values. Wigry National Park
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||