On the stability and resilience of the Lake of Shkodra

Transcription

1 Proceedings of the 2 nd International Conference Research and Education in the Natural Sciences, November 15-16, 2013 Shkodër Albania, Volume 1: On the stability and resilience of the Lake of Shkodra Dhimitër Dhora University of Shkodra Luigj Gurakuqi, Faculty of Natural Sciences, Department of Biology - Chemistry ABSTRACT For the first time are addressed both environmental characteristics of Shkodra Lake: stability and resilience. Lake of Shkodra is identified in one of two alternative stable state, characterizing shallow lakes, it with clean water and high abundance of submergent macrophytes. Three feedbacks that keep the water quality of the lake at normal parameters are given: the content of nutrients in the water and humic production from wetland; content of nutrients in the water and productivity of riparaian forest habitats; food chain structures that transfer phosphorus and biogeochemical mechanisms that inhibit recycling of phosphorus from sediments. Macrophytes are considered a key component of the ecosystem and a key factor of stability. They produce nutrients, serve as a link in the food chains, are more important habitats for animals, are inhibiting factors of nutrients recycling (especially phosphorus) from the sediment into the water, etc. Macrophytes are considered slow variable and as such promote resilience. Macrophytes destruction can lead to loss of resilience. While macrophytes and other key components, such as wetland, riparian forests ripariane, fish etc. are normal, intact, Shkodra Lake exhibits high resilience, face successfully the major perturbations. Factors influencing the high stability and resilience of the Lake of Shkodra are high fluctuation of the nutrients, food chains with no much links, as well as the large number of species that transfer phosphorus from the littoral to pelagial. Removing of the functional fishes group and discharging of organic pollutants can lead to loss of ecological resiliencës and consequently the loss of ecosystem stability. Development of social and ecological systems to be realized through two attributive objectives: keeping of the lake ecological resilience at high capacity, and increasing of the capacity of actors to influence resilience. Protected area status will bring more riches of species, greater functional diversity and less introduced species. Introduction With Ecological Stability we understand the ability of an ecosystem to coming back to its equilibrium position after a temporary disturbance (Gunderson 2000). As is writen in Fishbase (2013), an ecosystem is considered stable if it turns for a short time in its original state after a disturbance (resilience), presents low temporal variability (constance), or does not change dramatically despite the

2 shown disturbance (resistance). Ecological Resilience is defined as the capacity of ecosystem to absorb disturbances and implement changes without breaking the self-organizing structures, while maintaining essentially the same functions, structures, identities and feedbacks. Gunderson (2000) defines resiliencën as alternative stable state, as retention of restoration capacity in a dynamic environment; as ecological buffer that protects the system from the insufficiency of management actions. Holling (1973) introduced the word resilience in ecological literature to better understand the nonlinear dynamics of ecosystems. In the world scientific literature is written on stability and resilience of ecosystems only in these three - four decades. We don t know till today any publication on the stability and resilience of ecosystems of Albania and Skadar Lake. In this study for the first time are given considerations on stability and resilience of Lake Skadar ecosystem, their characterization, as well as the factors influencing in these ecological phenomena. Material and methods Different data, used in this work to argue our thesis on the stability and resilience of the Lake of Shkodra, are taken from publications, noted to the references. Thesis, for characterization of the stability and resiliece of the Lake of Shkodra, puted for discussion, are based in a new concept on the lake ecological valuation (Dhora et al. 2013) : the understanding of functional aspects with including of all ecosystem components. A lot of valuations and definitions are made in conformity to identity and condition of the Lake of Shkodra. Results and discussion are given according to questions. Results and discussion Identification of the alternative stable state According to Scheffer et al. (1993), Reuss et al. (2012), shallow lakes show two alternative stable states: - Turbulence stable state, with high phytoplankton abundance - Clean stable state, with high abundance of rooted macrophytes Lake Skadar, based on its characteristics (Dhora 2012), as it is written before (Dhora 2013), is identified in the second alternative, in the stable state with clean water and high abundance of rooted macrophytes. Feedbacks holding the water quality in normal parameters In Lake of Shkodra, as we wrote earlier (Dhora 2012, Dhora et al. 2013), based on Carpenter & Cottingham (1997), feedbacks holding the water quality in normal parameters are: 1. Nutrient content in water and the wetland humic production. According Wetzel (1990), Capacity Index of site for preservation of water and humic substances to be expressed with report: area of wetland / lake surface. We have calculated this index, and it is around 30%, which is considered high. 2. Nutrient content in water and the productivity of riparian forest habitats. Osborne & Kovacic (1993) has indicated the potential of nutrient input to the report: riparian area (occupied by forests) / area of meadows. When this ratio is high, the potential of the input is low. We have calculated this report, and comes around 0.3, but we have observed an increasing trend due to the increase of the riparian forests. 3. Structures of the food chain that transfer phosphorus (especially fish es) and biogeochemical

3 mechanisms (especially macrophytes) that inhibit the recycling of phosphorus from sediments. Such feedbacks can change only by the loss of the ecosystem resilience and consequently the situation can degenerate in undesirable surprises. Macrophytes - a key factor of stability, resilient slow variable Resilience loss can occur only with the changing of slowly variables. Referring to Gunderson et al. (2006) we selected such variables for the Lake of Shkodra: long term climatic factors, trophic relationships, habitat structures, nutrient production, nutrient levels in the sediment, etc. In most of these cases the macrophytes play a decisive role. Macrophytes produce nutrients, serve as a link of food chains, are the most important habitats for the animals, are inhibiting factors of the nutrient recycling (especially phosphorus) from the sediment in water etc. For Lake of Shkodra the macrophytes can be considered slow variable (with slow change), a key component of the ecosystem, which promotes resilience. Based on Vakkilainen (2005), we can argue how the submergent macrophytes modify food chain interactions and stability of the littoral ecosystem of the lake. Abundance of the submergent macrophytes and cladocera play decisive role in the littoral ecosystem stability and resistance (as a component of resilience, Holling 1973) to the nutrient increasing. If the abundance of macrophytes and cladocera decrease, phosphorus favors cyanobacteres, while nitrogen and phosphorus favor the chlorophytes and cryptophytes, as well as periphytic algae. Submergent macrophytes are protection shelter for zooplankton from the fishes. Cladocera benefits the shelter and holds the phytoplankton control. Roaches prefer cladocerian food, but when they abundanca decreased, these fishes use as an alternative the least favorite non-animal food. As long as the macrophytes, but also other key components, such as the wetland, riparian forests, fishes etc., are normal, intact, Lake of Shkodra shows the high resilience, successfully face (success is component of resilience) the major perturbations, both the floods and droughts. On the contrary, if the above components are vulnerable, then the situation gets out of control; she relocated to the human, economic, regional factors, more to the phosphoric balance of agricultural farms, to the regional development, fishing etc., and the perturbations to be translated into sustainable eutrophication symptoms. Factors that enable high stability and resilience According to Carpenter et al. (1992), in the following are treated, for the Lake of Shkodra conditions, three most important factors that influence to the stability and high resilience. 1. The high fluctuation of nutrients In the warmer seasons at Lake of Shkodra is produced a colossal biomass of aquatic macrophytes. In late of summer and autumn this biomass is decomposed and create a situation polisaprobike, with large quantities of the organic matter in decomposition. Further processes of decomposition and mineralization cause an increase of nutrients with phosphorus, nitrogen, etc. Fluctuation of the water level, from minimal to maximal, make this mass to be distributed in all lake sediment. Macrophytes developing in large areas are the main inhibition factor of the nutrient recycling, especially phosphorus, from the sediment in water. So high levels of nutrients, in water, down to low levels. This high fluktuacion of nutrient in water express the high resilience that characterizes the ecosystem. Thanks to this high resilience, Lake of Shkodra keeps the clean stable state, also in wide fluctuations of total phosphorus. 2. Food chains with non much links For argument we mention some main food chains: Phytoplankton - zooplankton - zooplanktivorous fishes piscivorous fishes Detrit - snails (detritvorous zoobenthos) - fishes piscivorous fishes

4 Plants - herbivorous fishes piscivorous fishes 3. A lot of species that transfer the phosphorus from the littoral to pelagial There are several thousands of tons of biomass containing phosphorus and other nutrients that is used as the food and transfered to the pelagial waters. Main role in transfer plays the fish component. Optic of the socio-ecological resilience Social resilience is the ability of human groups or communities to face with the stresses and trouble, arising from social, political and environmental transformations (Adger 2000). In this publication we treat only the social resilience, related to the environmental problems, namely socio-ecological resilience. Based on Janssen & Carpenter (1999), the dynamic of the lake can change in response to the management or surprises of the nature. In our publications (Dhora 2012 Dhora et al., 2012, 2013) are addressed the changes from floods, droughts etc. which are faced when the responsible components are intact, in consequence the ecosystem enjoys high resilience. The dynamic of the lake can also change in response to the management. We have got to Folk (2005) two factors, with management character, affecting more to the loss of the resilience of Lake of Shkodra: 1. Removing of the functional group. This can especially say for the fishes community, which may change due to poor management of fisheries, which brings destruction of structures, worsening of situations of fish populations. We think that the situation of the fish community is on the eve of the functional incapacity, and for many populations to the collapse. Low resources and threatened species show resilience weakness. 2. Unloading of organic pollutants, which currently, for the Lake of Shkodra, is the main cause of eutrophication. Also, the flow of organic solids, coming into the lake due to lack of antierozion investments and changes in land use of the Lake Watershed, stressing by Carpenter et al. (1997), are contributing to this phenomenon. These issues are addressed widely in recent studies (Dhora et al., 2012, 2013). If these two factors will continue for a long time, then we can face with the loss of the ecological resilience and in consequence of the ecosystem stability, and in the resulting with undesirable surprises in the socio-ecological systems. Gallaher (2007) wrote that in the context of global change, reconciliation between the economic development and environmental conservation, is today a growing call. He observe that, in the developing countries and rural areas, short-term economic needs take precedence over long-term environmental interests and this opinion he argues with the deforestation, overexploitation of resources, loss of biodiversity in many ecosystems and landscapes etc. Sustainable development as a concept was developed in the 80s in order to link the economic development and poverty alleviation with the environmental protection. The main objective of the management strategy of the Lake of Shkodra should be the development of social and ecological systems in the desired trajectory. Regarding this we can formulate two atributore objectives: the maintaining of the ecological lake resilience in high capacity, as well as the social adaptability, increasing of the stakeholders capacity to influence resilience. Differently, the ecological resilience to be determined by the feedback between the decision human making and ecological processes. The status of the protected area, which Lake of Shkodra enjoys on both sides, protects the ecological resilience of ecosystem. From this status, the lake profits higher species richness, greater functional diversity, less of introduced species. Gallaher (2007) emphasize that ecotourism can provide sustainable development in the developing countries and rural areas. It calls for a new concept of tourism, incorporating the theory of social-

5 ecological systems, investigation of the ecotourism through the lens of the social-ecological resilience. It is important to test the characteristics of ecotourism that cause different levels of the resilience. Testing According to options given to Lars (2007), we can considerate Shkodra Lake area with problems of a developing country, as relatively protected area, management with problems, overexploitation of fish resources, constructions in the protected area etc. Conclusions Lake Skadar clearly is identified as a shallow lake, in stable state with clean water and high abundance of submergent macrophytes. Feedbacks that keep the lake water quality in normal parameters, high nutrient fluctuation, as well as macrophytes, wetland, riparian forests, fishes and a lot of species that transfer phosphorus from the littoral to pelagial, food chains with not much links are factors that condition high stability and resilience of the Lake of Shkodra. Therefore the main objective of ecosystem management plans should be maintained intact. On the contrary, their destruction can lead to loss of the ecological resilience and in conseguence of the ecosystem stability. In management plans of the Lake of Shkodra should be included two atributory objectives relating to the development of social and ecological systems: maintaining of the ecological lake resilience in high capacity, as well as the social adaptability growth, increasing of the stakeholders capacity to influence resilience. Hopefully that the treatments on resilience and stability will contribute to diagnose and manage of Lake of Shkodra on a more scientific base. References ADGER, W. N. 2000: Social and ecological resilience: are they related? Progress in Human Geography 24, 3: CARPENTER, S. R., KRAFT, C. E., WRIGHT, R., HE, X., SORANNO, P. A. & HODGSON, J. R. 1992: Resilience and resistance of a Lake phosphorus cycle before and after food web manipulation. The American Naturalist, Vol. 140, No. 5: CARPENTER, S. R. & COTTINGHAM, K. L. 1997: Resilience and restoration of lakes. Conservation Ecology (online), 1 (1): 2. DHORA, DH. 2012: Liqeni i Shkodrës Camaj-Pipa. 130 fq. DHORA, DH., BEKTESHI, A. & RAKAJ, M. 2012: Investigation of Skadar/Shkodra Lake eutrophication level. Project financed by World Bank. Pp. 63. DHORA, DH., BEKTESHI, A. & RAKAJ, M. 2013: A new concept for recognizing of the eutrophication phenomenon in Lake of Shkodra. Buletin Shkencor i USh :Luigj Gurakuqi:, Nr. 63, Seria e Shkencave të Natyrës. FISHBASE 2013:

6 FOLKE, C., CARPENTER, S., WALKER, B., SCHEFFER, M., ELMQVIST, T., GUNDERSON, L. & HOLLING, C. S. 2005: Regime shifts, resilience, and biodiversity in ecosystem management. Annual Review of Ecology, Evolution, and Systematics, Vol. 35: (Volume publication date December 2004) GALLAHER, J. 2007: Ecotourism's Contribution to the Social-ecological Resilience of Protected Areas and Local Communities: A Comparative Analysis of Rural, Dryland Ecotourism in Costa Rica and Kansas. Catchment and Lake Research, LARS (2007). GUNDERSON, L. 2000: Ecological resilience - in theory and application. Annual Review of Ecology and Systematics, Vol. 31: (Volume publication date November 2000). GUNDERSON, L. H., CARPENTER, S. R., FOLKE, C., OLSSON, P. & PETERSON, G. D. 2006: Water RATs (resilience, adaptability, and transformability) in lake and wetland social-ecological systems. Ecology and Society 11(1): 16. [online] URL: HOLLING, C. S. 1973: Resilience and stability of ecological systems. Annual Review of Ecology and Systematics, 4: JANSSEN, M. A. & CARPENTER, S. R Managing the Resilience of Lakes: A multi-agent modeling approach. Conservation Ecology 3(2): LARS 2007: Catchment and Lake Research, 194 OSBORNE, L. L. & KOVACIC, D. A. 1993: Riparian vegetated buffer strips in water-quality restoration and stream management. Freshwater Biology, Volume 29, Issue 2: REUSS, L. M., ZIMMER, K. D., HERWIG, B. R. & HANSON, M. A. 2012: Stability of alternative stable states in shallow lakes. SCHEFER, M., HOSPER, S. H., MEIJER, M.-L., MOSS, B. & JEPPESEN, E. 1993: Alternative equilibria in shallow lakes. Trends in Ecology and Evolution 8: SCHEFFER, M. & EGBERT, H. V. N. 2007: Shallow lakes theory revisited: various alternative regimes driven by climate, nutrients, depth and lake size. Hydrobiologia, 584: VAKKILAINEN, K. 2005: Submerged macrophytes modify food web interactions and stability of lake littoral ecosystems. Academic dissertation in environmental ecology. University of Helsinki. WETZEL, R. G. 1990: Detritus, macrophytes and nutrient cycling in lakes. Mem. Ist. Ital. Idrobiol., 47: