Key-Descriptors for the Functioning of a Mediterranean Reservoir: The Case of the New Lake Karla-Greece

Abstract

Mediterranean freshwater systems face the lack of water as an important threat along with other multiple stressors (e.g., eutrophication, salinization, changes in hydrology and morphology) mainly attributed to human intervention. These stressors have been maximized due to the climate variability, the progressive diminishing of freshwater availability and the topography characteristics. Lake Karla is an example of a lake ecosystem which was dried in the 1960s and now is restored, facing various anthropogenic pressures. During the last 2 years (2010-2012) a 'new' shallow lake was reconstructed experiencing extensive alterations associated with land use changes, hydrological flow modifications, over-enrichment of chemicals, inappropriate management of biological resources. In terms of conservation value, Lake Karla is listed in Natura 2000 sites as a protected area. The aim of the present paper is to identify the key-descriptors highlighting the function of the new system, thus providing necessary 'tools' for an effective management plan. A 12-month monitoring study has taken place revealing the hydrological profile, the excess of in-lake nutrient concentrations, mainly attributed to the inflows and surface runoff, thus promoting a cultural eutrophication as it is also expressed by the high chlorophyll values. Relationships between nutrients and chlorophyll-a concentrations highlight the system's functioning. Yet, the classification of Lake Karla, as a highly modified water body, according to the Water Framework Directive, is discussed. Lake Karla serves as a paradigm on the multiple stressor effects and the complexity of biological restoration even though physical restoration has been established.