Effects of Anthropogenic Influences on the Trophic State, Land Uses and Aquatic Vegetation in a Shallow Mediterranean Lake: Implications for Restoration (original) (raw)
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Hydrobiologia, 2007
Land cover and land use changes affect ecological landscape functions and processes. Land use changes mainly caused by human activities, is a common reason for wetlands degradation worldwide. Lake Stymfalia, located at Peloponnese, southern Greece, is an ancient wetland with a great ecological value. Lake Stymfalia has been severely degraded and transformed during the past 60 years due to agricultural activities in the surrounding areas and watercourses alterations. In this context, we investigated the land cover/ use changes and the role of the reed beds in the terrestrialization process of this shallow wetland. This particular effort utilized remotely sensed data and Geographical Information Systems (GIS) techniques to estimate land use alterations for the period 1945-1996. Patch related landscape indices were generated to analyze impacts on landscape features. Spatial and thematic information concerning the surface area and the major land cover types of the lake for years 1945, 1960, 1972, 1987, 1992, and 1996 was obtained from aerial photographs and land surveys of the area, and was stored in the GIS database. The 1996 map was ground verified, corrected and updated to 2004 conditions. From the spatio-temporal analysis of the stored data, a permanent decrease of the open water surface has been observed between the years 1945 and 1996. The results indicated that the reed beds expanded dramatically, increasing by 89.3%, and is the predominant aquatic vegetation of the whole wetland. Open water areas and wet meadows decreased by 53.7 and 96.5% respectively. Landscape analyses and, in particular, the use of selected landscape metrics, proved useful for detecting and quantitatively characterising dynamic ecological processes. As land cover/use analysis of the wetland has shown much serious environmental degradation, conservation measures should be undertaken urgently.
Journal of Environmental Management, 2008
Lake Pamvotis is a shallow Mediterranean lake located in Western Greece near the city of Ioannina. The lake has been recognized as an internationally important conservation site under European Community legislation due to its rich biodiversity. However, during the last three decades the trophic status of the lake has changed as a result of anthropogenic activity (among others irrigation and domestic sewage discharge), resulting in serious problems. Here we present data about the long-term development in eutrophication of Lake Pamvotis. Water samples were collected and analyzed (water temperature, pH, dissolved oxygen, nutrients, chlorophyll-a) during three monitoring periods: 1985-1989, 1998-1999, 2004-2005. The high nutrient concentrations in the lake water during the three monitoring periods, as well as its eutrophic to hypertrophic status reflect the degree of impact anthropogenic activity has had on the lake. Commencement of a restoration plan in 1995-1996, involving sewage diversion, led to a reduction in external nutrient load and consequently to lower in-lake nutrients and Chlorophyll-a concentrations. Orthophosphate concentration decreased by about 87%, nitrates fell below 1.20 mg/l, whilst the total reduction of inorganic N compounds showed a weaker downward trend, fluctuating between 0.39 and 1.24 mg N/l with an average value of 0.76 mg N/l. However, after a short-term recovery the eutrophic status of the lake remains eight years later (2004)(2005), suggesting the importance of the internal loading process and the absence of the top-down effect of fish. This study provides evidence for the need of greater restoration efforts utilized in Mediterranean shallow lakes. r
Land Use Changes Do Not Rapidly Change the Trophic State of a Deep Lake. Amvrakia Lake, Greece
Journal of Environmental Protection, 2013
The study of physicochemical and biological parameters can assess the trend of a lake's trophic state. A trophic state index (TSI) was used to assess eutrophication of Lake Amvrakia. Total phosphorus and chlorophyll concentrations that recorded were generally at the same level with those recorded in previous years, a fact which indicates that lake's trophic state did not change. But in the past ten years, agricultural uses have been modified by almost 25% of the catchment area, because of the major reduction of tobacco cultivation. One year of monthly monitoring, in nine sampling stations can report this result. Even if the catchment is small and the agricultural areas are the 47% of the basin, the water quality of the lake did not change. The trophic state is stable probably because the lake is deep monomictic, and seasonally anoxic. For this reason internal phosphorus contribution is very important in the deep hypolimnion. 429 Figure 2. Monthly variation of temperature in Lake Amvrakia (2007-2008) from the station A5.
Environmental Processes
The national monitoring network of waters in Greece, in the context of Water Framework Directive (WFD), comprises 50 lake water bodies, both natural and artificial. The aims of the study are: (i) to present the pressures resulting from land cover and population density at river basin level; and (ii) to link catchment area features with physicochemical results from the first period of WFD monitoring. Land cover, population data in the catchment and physicochemical parameters were the main variables used in order to assess the lakes of the Greek WFD monitoring network. Intensive agriculture and urbanization, described as population density, proved to be the main pressure of severe impacted lakes as they were both highly associated with total phosphorus. Principal Components Analysis was used to position the Greek lakes along physical and chemical attributes, such as secchi depth, total phosphorus and ion concentrations and separate them according to their water quality. Clear reservoirs and natural lakes with high secchi depth were separated from more impacted ones with low secchi depth revealing a gradient of eutrophication, the most crucial anthropogenic pressure in Greece and in the Mediterranean area. The sustainable management of Greek lakes requires mitigation measures at a catchment scale, in order to regulate land uses, as well as site specific measures when needed.
Environmental impacts on Greek wetlands
Wetlands, 1997
This study identified the possible impact of anthropogenic activities on the ecological character of Greek wetlands. The objectives of this project were a) to record the anthropogenic activities that caused change in a wetland's ecological character and assess their intensity for each wetland site and b) to identify the most significant environmental impact on each type of Greek wetland. Nineteen factors of degradation (intensive human activities) were identified and grouped in one of the impact categories according to their most significant direct impact. These degradation factors were grouped into four categories for impact evaluation: change in water regime, depletion of wetland resources, change in water quality, and loss of wetland area.
Assessing the Ecological Water Level: The Case of Four Mediterranean Lakes
Water, 2020
The ecological water regime in lake water bodies refers to the water levels that enable the fulfillment of the ecosystem’s multiple functions. Therefore, assessing the ecological water regime necessitates the consideration of hydrological, economic, social, and ecological factors. The present research is focused on the assessment of the ecological water level of four Mediterranean natural lake ecosystems, considering their morphological and biological features. Initially, suggestions on the ecological water regime of the studied lakes were made based on an analysis of the lakes’ morphometry. Further, the ecological and biological requirements of the present fish fauna and aquatic macrophytic vegetation were considered. For the latter, mapping was conducted by extensive sampling according to international standards, in order to assess macrophyte composition, abundance, and chorology, as well as species sensitivity to water level fluctuations. The above guided the proposals on the opt...
Evaluating Impact of Land Use and Land Cover Change under Climate Change on a Lake System
Persistent pressures that relate to nonstationary climate variations and land use/cover changes (LULCC) keep affecting water resources and their associated environmental services with increasing impact trends worldwide. Lake Marmara, located in Gediz River Basin in Western Turkey, is already considered among the environmentally degraded water resources while counted with a priority wetland due to historical habitats and ecosystem functions. The region is remarkably threatened to its extinction under the combined impacts of both climate and LULCC related concerns. While intensive agricultural practices around the region deplete the lake's inflow sources, low levels of the lake water provide breeding ground for various algae types and cause eutrophication and related massive fish population decreases, in a way restricting local communities' access to fundamental ecosystem services for their survivability. The study investigates the effects of LULCC in the example of Lake Marma...
pan-ol.lublin.pl
The presented investigations were carried out within an agricultural landscape in the Wielkopolska Region. Their goal was to analyse changes in aquatic plant communities of various ecosystems (a lake, peat pits, a drainage ditch) during the last thirty-year period. The study showed that in the 1970s 18 plant communities occurred in the water column of the investigated ecosystems. That number decreased by 4 over the last thirty years. 9 plant associations disappeared. Eight among them are endangered in the Wielkopolska Region. The communities that disappeared preferred mostly slightly eutrophicated waters. They belonged to communities threatened with extinction as a result of increasing human pressure. On the other hand, the new associations are indicators of a high nutrient level in waters and nearly all of them belong nowadays to frequently occurring in aquatic environments of the studied area.