Abstract
In water management plans, all human impacts on the aquatic environment are quantified and evaluated. For this purpose, lake-related assessment methods of watersheds are needed. The aim of this study is to present the environmental condition along the watershed–lake continuum of Lake Baratz, located in the northeastern part of Sardinia. We provide a method to evaluate the impact of a small watershed area on the trophic state of this ancient Mediterranean natural lake. This study demonstrates the potentialities of coupling simple land structure-based models with empirical ones, allowing one to hierarchize, interpret, and predict the relationships among the watershed ecological unity and lake trophic conditions at multiple spatial and temporal scales. It also demonstrates how the impact of single and interacting nutrient stressors can have a different impact on the trophic status which, in particular, applies to autotrophs, constituting a key response in the ecosystem. We suggest that the stressor hierarchy should be considered as a way of prioritizing actions in the cost-effective implementation of conservation and management plans.
Highlights
Eutrophication has widely increased in inland waters worldwide over the past 50 years.Anthropogenic nutrient enrichment has been identified as the major cause for both observed elevated inorganic or organic nutrient concentrations and modified nutrient ratios [1,2].The main sources are the discharge of point wastewaters from urban, industrial, and zootechnical agglomeration and non-point pollution from intensive agricultural practices [3]
We evaluated the hypothesis of how the deterioration of the water quality and ecological integrity in the ancient Mediterranean natural Lake Baratz due to eutrophication is the result of watershed degradation from land use intensification
The analysis focused on evaluation of the land cover, using techniques of classification to generate polygons by clipping the shape of the most recent land use map [40], which was obtained by automatic classification of digital images of a medium spatial resolution (1:25,000)
Summary
Eutrophication has widely increased in inland waters worldwide over the past 50 years.Anthropogenic nutrient enrichment has been identified as the major cause for both observed elevated inorganic or organic nutrient concentrations and modified nutrient ratios [1,2].The main sources are the discharge of point wastewaters from urban, industrial, and zootechnical agglomeration and non-point pollution from intensive agricultural practices [3]. As an intermediate category causing nutrient pollution, overflows from urban septic and wastewater treatment plant systems and road or track runoff can be named [4]. The first observable effect concerns a significant increase in primary productivity and autotrophic biomass that cannot be efficiently controlled by consumers. The excess organic substance enters the detritus pathway, in which bacterial remineralization leads to oxygen depletion. This process feeds itself when, in addition to anoxic stress, toxic secondary products such as ammonia and hydrogen sulphide are generated, which further impair heterotrophs in the entire trophic web, generating anomalous changes in abundance and a reduction in diversity [2,6,7]. Cyanobacteria are most often responsible for the production and release of toxins following extensive blooms and are of great concern [8]
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