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Universiteti i Shkodrës “Luigj Gurakuqi”Bul. Shk., Ser. Shk. Nat., 2013. Nr. 63:

A new concept for recognizing of the eutrophication phenomenon in Lake of Shkodra

Dhimitër Dhora, Adem Bekteshi, Marash Rakaj

Faculty of Natural Sciences, University of Shkodra “Luigj Gurakuqi”, Department of Biology – Chemistry, Albania

ABSTRACT

Recognition of the phenomenon and level of eutrophication in Lake of Shkodra is done on a new concept, which is based on the recognition of the identity of the lake, feedbacks and responsible components that are involved in the dynamics of nutrients, as well as threatening factors for the development of this phenomenon.Lake of Shkodra is characterized shallow, with clear water, dominated by rooted macrophytes.Feedbacks holding in normal parameters the lake water quality are identified: the content of nutrients in the water and humic production in wetland; the content of nutrients in the water and productivity of littoral forest habitats; food chain structures that transfer phosphorus from littoral to pelagial and biogeochemical mechanisms that inhibit the recycling of phosphorus from sediments. Three main components of the ecosystem concerned with the phenomenon of eutrophication was given: wetland, macrophytes and fishes.Higher content of nutrients in littoral waters and lake botoms, as well as the abundance of macrophytes show on a normal development of the lake.The inverse saprobe-trophy relations, which has a great importance in creating of environmentally sustainable situations, were explained. Reduction of the saproby is associated with the increase of the trophy.Two factors are considered as the main causes for eutrophication of Lake of Shkodra: climatic, hydrologic and meteorological factors resulting from global warming, as well as the human factors, including the discharge of sewages and other organic materials with phosphorus (detergents); usage without criterion of chemical fertilizers in agriculture, whiches drain through karst formations

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of the lake watershed; increase of organic solid fllows from the watershed.The formulation and implementation of a long-term regional sustainable development strategy was considered as the most efficient way to eutrophication management, where the primary objectives were the protection of the main functional components, reduction of the input of nutrients and organic solid materials from the lake watershed, development of the organic agriculture and ecotourism.

Key words: eutrofication, fishes, Lake of Shkodra, macrophytes, nutrients, wetlands.

Një koncept i ri për njohjen e dukurisë së eutrofikimit në Liqenin e Shkodrës

PËRMBLEDHJE

Njohja e dukurisë dhe nivelit të eutrofikimit të Liqenit të Shkodrës bëhët me një koncept të ri, që bazohet në njohjen e identitetit të liqenit, feedback-eve dhe komponentëve pergjegjës që implikohen në dinamikat e nutrientëve, si dhe të faktorëve kërcënues per zhvillimin e kësaj dukurie. Liqeni i Shkodrës karakterizohet i cekët, me ujë të këthjelltë, i dominuar prej makrofiteve me rrënjë.Identifikohen feedback-et që mbajnë në parametrat normalë cilësinë e ujit të liqenit: përmbajtja e nutrientëve në ujë dhe prodhimi humik në wetland, përmbajtja e nutrientëve në ujë dhe prodhimtaria e habitateve pyjore të bregut, strukturat e zinxhirit ushqimor që transferojnë fosforin prej litoralit në pelagial dhe mekanizmat biogjeokimike që inhibojnë riciklimin e fosforit prej sedimentit.Jepen tre komponentët kryesorë të ekosistemit që lidhen me dukurinë e eutrofikimit: wetland-i, makrofitet dhe peshqit. Përmbajtja më e lartë e nutrientëve në ujërat e brigjeve dhe fundet e liqenit, si dhe abundanca e makrofiteve, janë shprehje të zhvillimit normal të liqenit.Shpjegohen marëdhëniet inverse saprobi-trofi, të cilat kanë rëndësi të madhe në krijimin e situatave të qëndrueshme ekologjike. Ulja e nivelit të saprobisë shoqërohet me rritjen e nivelit të trofisë. Dy faktorë konsiderohen si shkaktarët më kryesorë të eutrofikimit të Liqenit të Shkodrës: faktorët klimaterikë, hidrologjikë dhe metereologjike, prej ngrohjes globale, si dhe faktorët njerëzorë, ku përfshihen shkarkimet e ujërave të zeza dhe lëndëve të tjera organike me fosfor (detergjentëve); perdorimi pa kriter

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i plehërave kimike në bujqësi, që drenojnë nëpër formacionet karstike prej pellgut në liqen; shtimi i prurjeve të ngurta organike prej Pellgut Ujëmbledhës.Si rruga më efikase në menaxhimin e eutrofikimit konsiderohet for-mulimi dhe implementimi i një strategjie afatgjatë të zhvillimit të qendrueshëm rajonal, ku objektivat primare të ishin mbrojtja e kom-ponentëve kryesorë funksionalë, reduktimi i inputit të nutrientëve dhe lëndëve të ngurta organike prej Pellgut Ujëmbledhës në Liqen, zhvil-limi i bujqësisë organike dhe ekoturizmit.

Introduction

Eutrophication of the lake is a natural process, caused by the gradual accumulation of nutrients, the gradual increase productivity, and slow filling of the lake basin. Eutrophication is also called the aging of the lake. In natural conditions, it develops slowly and the development of the phenomenon is measured in geological time.As is well known, the base concept for trophic classification of lakes is nutrient enrichment and productivity. An oligotrophic lake has low nutrient concentrations and low productivity. A eutrophic lake has a high concentrations of nutrients, especially phosphorus and nitrogen, and high productivity. Mesotrophic lakes are somewhere between eutrophic and oligotrophic lakes.From the mid-twentieth century eutrophication is known as the problem of pollution in lakes of Europe and North America. Later the concept was extended further. Today 54% of lakes in Asia are eutrophic; Europe 53%; North America 48%; South America 41% and Africa 28% (WIKIPEDIA). Discharge of organic matter and agricultural chemical fertilizer rich in phosphorus and nitrogen accelerate extremely eutrophication process.The problem of eutrophication of Lake of Shkodra has long been in the public and scientific research attention. Especially during the last four or five decades, it has amassed a great number of publications on various aspects related to the content of nutrients in the waters of Lake of Shkodra, identification of the eutrophication phenomenon in different habitats based on chemical and biological indicators.In generally the data from these studies have ascertain character; in them lack the accurate and complete reply on responsible structural and functional factors of eutrophication in lake. In this overview article, for the first time, a new concept for the recognizing of the eutrophication in Lake of Shkodra was developed, which is based on the identity of the lake, feedbacks and responsible components in the

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dynamics of nutrients, as well as threatening factors for the development of this phenomenon.

Material and methods

Data on the content of nutrients in the water and sediment were taken from the literature listed at the end, especially BEKTESHI (1997, 2007, 2011).Determination of phytoplankton diversity is based on SHANNON (1948), while the index of trophy to BECK (1955).Assessment and classification of habitats is made in accordance with MedWet Habitat Description System (HECKER et al., 1996) modified by EKBY (Thessaloniki), more or less as recorded to DHORA (2005), but here are presented in a concise form.The study of the flora and vegetation is also made according to literature (RUCI 1986, KASHTA & RAKAJ 2001; DHORA 2005; DHORA & RAKAJ 2010; RAKAJ 2009; RAKAJ & KASHTA 2010, 2011), as well as to some unpublished notes.For fishes, the list published by DHORA (2012) with relevant comments is used.Fish food regime of adult species with higher abundance and market important, as well as piscivore links are obtained mainly from KOTTELAT & FREYHOF (2007), fishbase.org and RAKAJ (1995).

Results and discussion

1. The identity of Lake of Shkodra

According to SCHEFFER & VAN NES (2007) shallow eutrophic lakes exist in two alternative situations:a) The turbulent and dominated by phytoplankton. Increasing large phytoplankton and the creation of the state of turbulence is related to the recycling of nutrients, especially phosphorus from sediments into the water. This development prevents growth of rooted macrophytes.b) The clear and dominated by rooted macrophytes, including benthic multicellular algae. Massive growth of rooted macrophytes inhibits recycling of nutrients from the sediment into the water.Based on this division, we can characterize the Lake of Shkodra, quite clearly, in the alternative situation, as shallow eutrophic lake, with clear water and dominated by rooted macrophytes. To explain this definition, we give below three of the characteristics of the

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lake, taken from DHORA (2005, 2012), which relate to its stable ecological situation:- Lake of Shkodra is characterized as environment with littoral character. Shallowness and the water level oscillations make impossible the developing of vertical zone in the Lake.Lake of Shkodra is considered simply as littoral character environment. It is relatively a shallow lake, with a maximum depth of 8 meters (without cryptodepressions), located at an average 4.5 m height above sea level, and with fluctuation water level up to 3 meters.Its sediments are generally within photic zone. Shallowness and high turbulence, due to the strong wind, accelerate redox transformations of sediment, with positive direction, facilitated connections and interaction of water with sediment.- Lake of Shkodra is characterized by large macrophytes areas. Macrophytes are the most characteristic feature of the littoral and the whole water body of the lake. Macrophytes are developed from the shore to depths, ranging from emergent associations, stereotypically dominated by Phragmites australis, to associations with floating leaves, dominated by Nuphar luteum, Nymphaea alba dhe Trapa natans, further those submerging, with dominance of Myriophyllum spicatum, Ceratophyllum demersum, Potamogeton and Ranunculus aquatilis and ending to deepest associations with dominance of Vallisneria spiralis, Najas marina and Charophyta.- Lake of Shkodra represent a cryptodepression. 165 km² of bottom surface of the lake, which belongs to about 44.3% of the minimal surface of Lake of Shkodra is located below the sea level. This phenomenon characterize this lake as a rarely known cryptodepression in Europe and Globe. Cryptodepressions of the Lake of Shkodra have deeper and clean water springs in their bottom. These are mainly located along southwest coast, north and east of the lake. Littoral waters and sediment of the lake are characterized as eutrophic environments (Figure 1-4). In the warmer months, the content of phosphorus, as the most significant indicator of eutrophication, in lakeshore results in an average 0.36 mg / l, while in the sediment of the lake a few more times, whereas in littoral goes up to 20 times.

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Figure 1.Minimum and maximum concentration of total nitrogen (mg/l)

Figure 2.Minimum and maximum concentration of total phosphorus (mg/l)

Figura 3. Minimum and maximum values of chlorophyll a (mg/m3)

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Figura 4. Minimum and maximum values of transparency, estimated by Secchi Disc (m)

OLSEN (1966) believes that there are three ways by which phosphorus embedded in sediment: biologically, of metabolic processes in bacteria, phytoplankton and macrophytes; chemically by reaction with calcium, iron and aluminum; sorption, where phosphorus is fixed on the surface of solids. Saturation of oxygen in water is 70% and in our analysis has gone even higher. In particular, it is important the presence of hypolimnetic oxygen (CORNETT & RIGLER 1979, CARACO 1993), which in Lake of Shkodra is a reality, because of the small depth of water, turnover of waters etc.Oxygenated sludge surface develops a high redox potential. In these circumstances, we think that the three the possibilities of transfer of phosphorus in sediment were realized (MORTIMER 1971).Eutrophication indicator species, as was written to DHORA et al. (2012), show frequency and high dominance in lakesides. Species Nuphar luteum, particularly indicates clearly eutrophic environment in outlet of Buna River, smooth littoral in Dobraç, Gashaj in Albania and in many other localities in the Montenegrian part. The dominance of larvae of Chironomus plumosus in benthos, but according JANKOVIC (1981) 15 - 20 times more on littoral than in the open waters of the lake, was related to preferences of stagnant water, eutrophic, with sludge substrate, with plenty organic detritus rich in protein and lipids which is fed to an important part of life.We believe that high abundance of Bosmina longirostris in Lake of Shkodra (KRALJ 2011), which according to GASIOROWSKI & SZEROCZYNSKA (2004) is an indicator of eutrophication, is related to the seasonal development of phytoplankton.

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In warmer seasons, but especially in the spring and fall, when nutrients are higher in water content, especially of lakesides, as was written to DHORA et al. (2012), increased phytoplankton and its species indicates environments more alfa-mesotrophe, or even eutrophe, but the situation improved by other factors, such as the transfer of phosphorus in sediment, increase of water level, consumption of phytoplankton by added biomass of zooplankton etc.

2. Feedbacks that keep the nutrients in waters of Lake Skadar in normal parameters

Referring for the analogy to CARPENTER & COTTINGHAM (1997), feedbacks that keep in normal settings water quality parameters in Lake of Shkodra are: -The content of nutrients in the water and humic production in wetland. Humic production was dedicated to the wetland. As is known, in the warmer seasons, when the water level drops significantly, in littoral waters of the lake and surrounding basin swamps are developed luxuriant vegetation macrophytes. Macrophytes constitute the main source of nutrients.- The content of nutrients in the water and productivity of riparian forest habitats. Along shallow littoral of the lake is whole forest area, composed mainly of willows, poplar, ash, etc. They have a limiting ecological role in the development of macrophytes in areas where do shade. - Food chain structures that transfer phosphorus from littoral to pelagial and biogeochemical mechanisms that inhibit recycling of phosphorus from sediment. Among the transferred structures of nutrients, as the most important we can consider the fishes.

3. Key components of the ecosystem of the Lake of Shkodra

Looking at the whole of the nutrients dynamics we can appreciate that key components of the Lake of Shkodra are wetland, macrophytes and fishes.

WetlandLake of Shkodra represents a large-scale habitat, interesting, unique and very complex. These features are related mainly to water regime, which varies according to the seasons, with the fluctuation of water levels. The Lake of

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Shkodra that is characterized as shallow, develop the fluctuations more on the surface than in depth. This causes during the warm season, especially in the north, but and east and southeast, the developing of a large marshy area.Lake of Shkodra consists of three systems of habitats.a) Lacustrin system, that includes two subsystems habitats. Limnetic subsystem includes habitats constantly flooded of the water surfaces: class with muddy substrata and the class of vegetation, which can be various. Littoral subsystem comprises several habitats classes: water surfaces that may have different substrata, continuously or seasonally flooded; class without vegetation, with various sediments, continuously or seasonally flooded; class with different rooted vegetation, continuously or seasonally flooded (especially in north, east and southeast littoral ,where these habitats are widespread); emergent vegetation class, with different water regime.b) System palustrine (marshy surfaces created by the withdrawal of lake water in warmer seasons, occured especially in the north, east and southeast) includes several habitats classes: class of water surfaces with different substrata, constantly or seasonally flooded; non vegetated class with different substarta, constantly or seasonally flooded; class with different rooted vegetation, constantly or seasonally flooded; emergent vegetation class (these are most palustrine surfaces with persistent vegetation) with very different water regime; class of shrub vegetation, mainly deciduous, with very different water regime (where, muddy and rocky shorelines, but not very developed); deciduous forest vegetation class, with different water regime (particularly occured in northern, eastern and southeastern part of lake).c) Riverin system has two subsystems: alternate subsystem (habitats in outlet of streams, as Përroi i Thatë and others) non vegetated, rocky or sandy, or seasonal flooded from time to time, as well as permanent subsystem (such as the beginning of Buna River from the lake). This subsystem has four classes of habitats: the surface of the water, with different substrata, constantly flooded; non-vegetated, with different substrata, constantly flooded; with different vegetation, constantly flooded; emergent vegetation, not persistent, with different water regime.Report wetland area / lake area expressed index of site-s capacity to hold water and humic substances (WETZEL 1990). As we said, the lake water fluctuations was developed more on the surface than in depth and this increase amounts to 170% of the minimum area of the lake, This phenomenon happens in seasons with a maximum precipitation. With increasing temperature and decreasing precipitation, a soft marshy area next to the lake was developed,

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that maximally up to 30% of the surface of the lake, but in the warmer months down more. However, the value of this index could be considered high for the Lake of Shkodra.

MacrophytesIn Lake of Shkodra are found 240 species of plants, of whiches 61 hydrophytes and 179 herbaceous species of different moisted environments. 22 of them are single trees and shrubs or woody spots of willows, white poplar, alder, narrow-leafed ash, tamarix, chaste tree or invasive false indigo.From 61 aquatic species (hydrophytes), 17 species are floating on the water surface, while 45 species are immersed in water (submergent), or terminal parts immersed in water and the upper part of the plant above the water (emergent).Macrophytes of the lake belong to 4 taxonomic groups of plants: 10 species are algae (Characeae), 1 moss, and about 8 species are horsetails and ferns, others are flowering plants (Angiosperma), 113 Monocotyledons and 106 Dicotyledonous.Species with greater frequency and cover in wetland or damp areas and lake waters are: Schoenoplectus lacustris, Phragmites australis, Typha sp. div., Sparganium erectum, Potamogeton perfoliatus, Potamogeton lucens, Potamogeton crispus, Ceratophyllum demersum, Miryophyllum spicatum, Nuphar lutea, Nymphaea alba, Trapa natans, Valisneria spiralis, Najas marina, Najas minor, Ranunculus trichophyllus, Gratiola officinalis, Sagittaria sagittifolia, Fontinalis antipyretica.Plant species of wetland and lake water belonging to these groups in biological life forms:1. Hydrophytes - plants with leaves over water or under water, including 4 subgroupsa. Hydrochemicryptophytes - underwater plants as Vallisneria,b. Hydrogeophytes - rooted plants with leaves on water (Nymphaea, Nuphar, Nymphoides), c. Hydroterophytes – non-rooted plants with leaves on water (Lemna, Spyrodela, Utricularia)d. Hydrochamaophytes - rooted plants with underwater leaves (Potamogeton, Najas, Groenlandia, Zanichelia),2. Hygrophytes or Helophytes - hemicryptophytes or wetland plants, such as marshes plants (Typha, Sparganium, Sagittaria, Alisma, Butomus, Hydrocotile, Ranunculus)3. Geophytes - bulb plants (Leucojum, Iris, Orchis, Gladiola, Serapias),

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4. Fanerophytes - tree, shrub or herbaceous flowers that emerge in height over 2 meters (Populus, Salix, Alnus, Fraxinus, Tamarix, Vitex, Arundo). This group includes three distinct subgroups:a. Liane - plants that cling on other trees (Periploca graeca, Vitis sylvestris, Solanum dulcamara, Humulus lupulus, Clematis viticella),b. Epiphyte or lithophyte – non-parasitic plants that grow on trees or on stones (lichens, mosses),c. Holoparasitic - parasitic plants completely dependent on the host organism (Orobancha),5. Hemicryptophytes - perennial herbaceous plants of moderately wet soils to dry (Phragmites, Schoenus, Eleocharis, Juncus, Carex),6. Terophytes - annual plants of wet lands (Cyperus, Pycreus, Fimbristylis).Subtropical climate, karsts terrain, mostly flat character of the lake, shallowness and diversity of habitats (lake, littoral, swamp, rivers, springs, etc.), have created very favorable conditions for a great development of macrophytes vegetation, particularly the herbaceous. Because of the nature of the littoral, the vegetation is more developed in the north-eastern, eastern and south-eastern part of the lake.Along lakeshore or wet soils, seasonally flooded, dominate emergent plant communities with high stem (Phragmites, Scirpus, Typha, Sparganium, Cyperus, Carex), that together with the community of floating plants (Nuphar, Nymphea, Trapa) growing in marshy area and shallow waters constitute the major biomass and productivity of the lake.In open waters up to the depth of 3.5 - 4 meters grows a submergent macrophytes community with short stem (Najas marina, Vallisneria spiralis, Ceratophyllum demersum, Myriophyllum spicatum, Potamogeton sp., Chara, Nitellopsis etc.) that often create the underwater meadows (aquatic beds). We know recently 47 of aquatic and marshy plant associations, published mostly by LAKUŠIĆ & PAVLOVIC (1981) etc, which are arranged, listed and presented by DHORA (2005).Report riparian area, occupied by forests / meadows, influence in reducing of the input of nutrients (OSBORNE & KOVACIC 1993). Based in some data maps and publications, we have estimated that this ratio is about 0.2. We believe that this report will be increased because of increasing the littoral forest areas. This phenomenon we consider as a positive development.

FishesLatest list of fish species of Lake of Shkodra is published by DHORA (2012).

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The list of fishes of Lake of Shkodra contains 52 species. Cyprinidae family includes 25 species, i.e. 48% of the total species, a fact that characterizes this lake as deeply ciprinid. Salmonidae family ranks second with 9 species, or 17.3% of the total number of species of the lake.Of the general number of 52 species, 35, or 67.3.6% are considered native species, among them the important market species Cyprinus carpio, Alburnus scoranza, Scardinius knezevici as well as two species of genus Rutilus. While 16 species or 30.8% are allochtone and of these 9 are introduced by human, through restocking over the past 3 - 4 decades. All of these fishes was slowly decreased because of lack of restocking since the 1990s, while only prussian carp, Carassius gibelio is completely adapted to living in the lake. Last two or three decades is added allochtone species Perca fluviatilis and now is considered as one of important market fish.Other 8 species are migrating to the sea, and among them Mugil cephalus, Liza ramado, Anguilla anguilla and migration Alosa agone.The transfer of nutrients from the littoral to pelagial are realized from fishes and this phenomenon is related to their food spectrum.Complex lake fish food regime is characterized by a structure herbivore - detritus. The most important plant species for the fishes food are those of the genus Potamogeton, Myriophyllum, Ceratophyllum, Vallisneria etc. From our study on the food spectrum we can to mention the herbivore fish species of the Lake of Shkodra: Cyprinus carpio, Scardinius knezevici, Carassius gibelio, species of genius Rutilus (as optional herbivore) etc. Detritus, produced by macrophytes serves as the basis for food of fish species, as Mugil cephalus, Liza ramado, Carassius gibelio, Chondrostoma nassus, Squalius platyceps, as well as invertebrate benthic food base, which are food for Cyprinus carpio, Carassius gibelio, Anguilla anguilla, Squalius platyceps and juvenile forms of the different species, which may be mentioned Perca fluviatilis etc. Finally add that several species are planktivore and most important mention Alburnus scoranza, and some other piscivore, which can highlight Anguilla anguilla, Squalius platyceps, Perca fluviatilis, non-migratory Alosa agone, trout (Salmonidae) etc.

4. Seasonal eutrophication in Lake of Shkodra - regular succession

In late summer, under minimum conditions of water and maximum of temperature, macrophytes biomass begins to be decomposed.Decomposition of organic matter to ammonium and sulfur continues in littoral

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during autumn, creating a quite heavy saprobic situation. The saproby is the decomposition of organic substances. It is influenced by many indicators, especially oxygen and invertebrate animal community composition.The situation improved with the increase of water level of the lake in the early months of rainfall. Decomposed biomass are dissolved in lake sediment and move toward the Buna River and the sea.Decomposition continues in the water up in simple substances containing phosphorus, nitrogen, etc. Thus, in the waters of the lake, particularly of littoral and sediment, content of nutrients, especially those containing phosphorus, as the main indicator of eutrophication, are increased. In terms of the Lake of Shkodra, where the sources of organic matter are internal (macrophytes), the equilibrium is reached between saproby and trophy, so is reduced the level of saproby, but increased the level of trophy (of nutrients in the water). Inverse saproby - trophy relations are of great importance in creating environmentally sustainable situations.In terms of the presence of hypolimnetic oxygen, phosphorus passes from the water in sediment through three possibilities, as described above. Nutrients of the sediment are used for the development of macrophytes and invertebrates of the next year. Macrophytes are the main recycling inhibitor of nutrients from sediment to the water.

5. Threatening phenomena of the eutrophication in Lake of Shkodra

A. Eutrophication from extreme fluctuations of water levels.If the water level goes beyond acceptable parameters, minimal or maximal, then the whole ecosystem or its components, are made hypersensitives and consequently the developments are fragmented from the system and tend to go towards the ecological degradation.a) When the water level goes over the maximum acceptable parametersIn situations of maximal fllow of Drin and Moraça rivers, forced discharge of water from hydropower dams gates up to 7,500 m³ / sec and more, as well as the inability to sea water removal, was caused flooding in the lowland region of hydrological system of the Lake of Shkodra – Buna River - Drin River, with major ecological and social consequences.We think that the large water flows have been associated with the large inflows of organic solids, much more than in normal situations. These large inflows have been the reason for the increase of aquatic macrophytes in these last years, but in subsequent years are stabilized in optimal situations. As we mentioned

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above, the components of the lake, participating in the dynamics of nutrients of the Lake of Shkodra have high potential and have faced relatively well the difficulties of ecological situations of floodings, that to be eventually occured.b) When the water level goes below the minimum acceptable parameters.This situation may arise due to prolonged drought, limitation summer water discharges from power plants etc. This situation has dominated in recent years. Reducing beyond reasonable threshold water level is also considered destructive phenomenon. Due to the reduction of the water level would increase the temperature, which would again lead to a eutrophicated situation.Control components in the lake have remained intact, indicating that this difficult situation, with the first alternative, is faced with success. We think that the data of VIZI (1997) on the increasing of macrophytes in Vucko Blato, on both sides of Moraça and Humsko Zaliv, also different opinions on increasing of macrophyte surfaces in the Albanian part of the lake, especially at the beginning of Buna River, can be interpreted as a result of the strong influence of these unusual phenomena.

B. Cultural eutrophicationOne of the main sources of nutrients is colossal solid flows due to erosion. According to KOVAC et al. (2011) Lake of Shkodra basin is estimated as surface with potential and actual erosion risk.In this basin, always according to these authors, has a quite favorable base for erosion: on limestone are structure with high erodibility and erosivity, terrains are generally steep or very steep, and plant cover is downward. It is estimated that over 74% of the watershed lands have high potential risk of erosion, as well as 85% of the lands have current moderate risk of erosion.The destruction of forests is another major cause of erosion. Forest in the catchment area, compared to 100 years ago, has come down significantly.Planty solid flows, coming through flowing water in the lake, are rich in organic matter, which constitute an additional source of nutrients in the lake. These solid flows are today growing because of the increased erosion.Another source of nutrients are fertilizers rich in phosphorus and nitrogen, which are used in agriculture and drain from watershed to lake. Lake of Shkodra watershed should be considered agricultural, especially because of the large agricultural area in the field plains Zeta-Shkodra. Currently, though this area is not used intensively and completely, the chemical fertilizers are used in large quantities. It is anticipated that the use of chemical fertilizers to grow in the future, because the chemical agriculture will be developed

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much more than the organic agriculture. Lake, affecting especially from an agricultural watershed, increases the nutrient content. This phenomenon is dependent on the time of use and drainage to the lake of fertilizers. We believe that the nitrogen is increased to the lake from this source more in the spring, and is decreased in the summer, when is increased phosphorus.Another source of nutrients is discharge of wastewater directly into the lake. Wastewaters are a major source of pollution with organic matter that are decomposed increasing the level of water saproby, particularly of littorals. Must of cities and other inhabiting areas of the watershed of Lake of Shkodra, including Podgorica, Cetinje and Niksic, discharge their wastewater directly into the main affluent of the lake, in Moraca river. Wastewater of Shkodra city currently discharged at Ura e Bahçalleku on the River Drin, but the flood of 2010-s in Shkodra showed that those, by the Buna reverse flow, got to the lake.In some cases, for major reasons, discharge is carried in the meadows of the lake, probably in outflow of Buna river from the lake. Should be taken into account also small towns like Koplik, Bajza, Tuzi, Virpazar, etc., are steadily increase and that, in the absence of treatment process, will discharge no small quantities of sewage into the lake.Another source of nutrients with phosphorus content are detergents that income into the lake mainly by waters.As can be seen the phenomenon of cultural eutrophication in Lake of Shkodra is mainly related to poor management of the watershed.Present situation of the Lake of Shkodra is problematic, but not ireparable. Of a serious engagement, especially of responsible factors and actors, to decrease the cultural eutrophication by the reducing of the nutrient inputs from surrounding areas into the lake, the situations, that we believe that are reversible, will be stabilized.

Conclusions

For the first time is formulated a new concept for recognizing of eutrophication in Lake of Shkodra, which is based on the identity of the lake, feedbacks and responsible components in the dynamics of nutrients, as well as threatening factors for the development of this phenomenon.All data indicate that the waters of the Lake of Shkodra are oligotrophic. Higher indicators of nutrients content, particularly of phosphorus, in the littoral waters and bottom of the lake, macrophytes development and the presence of several biological indicators of eutrophication in these habitats, are indicative of the normal development of the lake. They are related to decay and chemical

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transformations of a colossal aquatic macrophytes mass, with the great deal of detritus created in the upper sediment layer, with high abundance of bacteria, periphyton and many other living creatures.Feedbacks that control water quality, as well as responsible components show high potential, stability and resistance.Nutrients are produced by rooted macrophytes of wetland. Should be evaluated keeping in normal parameters of the raport between wetland’s surface that produce nutrients and the lake surface. Observed trend of increase of forests in littoral may be considered as a positive development to prevent eutrophication.Rotting on the littoral of the biomass is accompanied by the creation of a saprobe situation which is related to the development of eutrophic situation.The transfer of nutrients from the littoral to pelagial is mainly realized by fishes. For this main functional component of the lake is required to be implemented management measures that ensure sustainable development of the fish community and fishing.Nutrients that are transferred from water in the sediment will be used for the development of macrophytes and invertebrates next year. Macrophytes are the main inhibitors of the nutrients recycling in the water.Maintaining of the water quality in normal parameters to be also favored by lake hydrological characteristics, where we distinguish the seasonal water level fluctuation and cryptodepressions, with no small water flow.In our opinion, the eutrophication phenomenon in Lake of Shkodra is not the result of long-term developments, but of cyclical character ones. Seasonal eutrophication is considered a seasonal normal development, a regular succession, that determine the ecosystem existence.Two factors may be considered as the main eutrophication causes of Lake of Shkodra:a) Climatic, hydrologic and meteorological factors of global warming.Data and opinions belong to specific areas or specific hydrological and meteorological conditions.Development of the macrophytes vegetation identified last years was related to the low level of water in the summer due to prolonged drought and consequently the increase of water temperature.On the other hand increase of organic solids flows in flood times, favored this phenomenon of erosion due to the deforestation and lack of anti-erosion investment, has brought in subsequent years increased aquatic vegetation.b) The human factors, including discharge of sewage and other organic materials with phosphorus (detergents); out criterion usage of chemical fertilizers, which drain through karst formations from watershed to the lake;

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massive deforestations and lack of anti-erosion measures in the watershed of Lake of Shkodra, all influence in increase of organic solid fllows.Best way to manage the eutrophication is to be formulated and implemented a long-term strategy of sustainable regional development, where as primary objectives to be identified the protection of the main functional components (wetland, macrophytes, littoral forests and fishes), reduction of nutrients input from the watershed to the lake, development of organic agriculture and ecotourism.

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WIKIPEDIA, the free encyclopedia: http://www.docstoc.com/docs/6129339/eutrophication