Portuguese shallow eutrophic lakes: evaluation under the Water Framework Directive and possible physicochemical restoration measures
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Eutrophication has become the primary water quality issue for most of the freshwater ecosystems in the world. It is one of the most remarkable examples of the biosphere’s alterations due to agricultural and industrial activities affecting aquatic ecosystems. As eutrophication becomes frequent and many eutrophic ecosystems have difficulties in meeting the EU Water Framework Directive (WFD) criteria, the removal of phosphate gains great importance in water treatment. The objective of this study is to highlight the remediation methods that have been implemented in Portuguese eutrophic shallow lakes to accomplish the WFD requirements, particularly for the control of external loading of nutrients. However, the reduction of external nutrient loads per se often does not result in a change back to the original state, and additional internal lake restoration measures may therefore be needed to decrease the concentration of total phosphorus and increase water quality. In this context, this review paper also describes the chemical approaches available to mitigate the eutrophication of shallow freshwater ecosystems based on phosphate inactivation agents, their capacity and application methods, as well as the results that generically have been obtained. The P-inactivation agents can also be complemented with physical approaches in order to improve the treatment effectiveness. Although these remediation techniques can have significant benefits in reducing the proliferation of cyanobacterial blooms, other potential adverse ecological effects may occur. For this reason, the costs, the application strategy, the potential stressor(s) effect(s), both for human and key species, are factors that should be taken into account before its effective application.
KeywordsEutrophication Shallow eutrophic lakes Water Framework Directive Restoration measures
This work was supported by Portuguese Foundation for Science and Technology (FCT—Fundação para a Ciência e Tecnologia) through individual research grant reference SFRH/BD/48597/2008, under QREN—POPH funds, co-financed by the European Social Fund and Portuguese National Funds from MEC. CESAM is supported by FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020 (UID/AMB/50017). Finally, CIIMAR is supported by the Strategic Funding UID/Multi/04423/2013 001 through national funds provided by FCT/MEC—Foundation for Science and Technology and European Regional Development Fund (FEDER), in the framework of the program PT2020.
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Conflict of interest
All authors declare that they have no conflicts of interest.
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