Ecological integrity assessment in aquatic ecosystems: A multi-scale approach towards the definition of the ecological status of Mediterranean reservoirs
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2008
Autores
Sampaio, Edna Carla Janeiro Cabecinha da Câmara
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Mundialmente os sistemas aquáticos têm sido afectados por diversas pressões a larga escala, nomeadamente a intensificação agrícola e o aumento de fontes tópicas e difusas, que se sobrepõem no espaço e no tempo e têm levado à ruptura da estrutura e do funcionamento destes sistemas. Face a esta alteração global, o declínio da qualidade ambiental dos rios e respectivas albufeiras, tem sido alvo de uma crescente preocupação. Neste contexto, tem surgido uma crescente procura de novas tecnologias para a monitorização de albufeiras que permitam estabelecer prioridades de conservação, protecção e restauração, que possibilitem alcançar o estado ecológico requerido ou um bom potencial ecológico para estas massas de água fortemente modificadas. Assim, o objectivo desta tese foi o desenvolvimento de novas ferramentas assentes em análises estatísticas multivariadas e metodologias de modelação, que possibilitam a determinação do estado ecológico de albufeiras mediterrâneas, no âmbito da Directiva Quadro da Água DQA). Este trabalho pretende desenvolver metodologias integradas que captem a complexidade inerente aos ecossistemas aquáticos através de uma abordagem multi escala, de modo a compreender melhor os mecanismos locais e regionais que operam nestas massas de água. Para uma melhor compreensão das alterações ocorridas na estrutura e funcionamento das albufeiras, vários componentes destes ecossistemas foram incorporados a diferentes escalas temporais e espaciais de análise, nomeadamente, parâmetros hidromorfológicos, físicos, químicos e biológicos e ainda vários factores de perturbação (i.e., alterações dos usos do solo, variações hidrométricas e fontes de poluição tópicas e difusas). A tese foi estruturada em sete capítulos cuja análise foi suportada por extensas bases de dados, nomeadamente as séries temporais de longo-termo, referentes ao período 1996-2004, compiladas pelo Laboratório de Ambiente do Grupo Electricidade de Portugal (EDP, LABELEC). A base de dados engloba um conjunto de 34 albufeiras que se estendem por cinco regiões hidrográficas distintas (Bacias do Lima, Cávado e Ave, Douro, Mondego e Tejo). Os principais objectivos desta tese foram:
Estabelecer a tipologia e as condições de referência de cada Tipo, das albufeiras Portuguesas com fins hidroeléctricos definidos, através de uma abordagem multi escala baseada nos elementos abióticos e bióticos, nomeadamente nas comunidades fitoplânctonicas como indicadores da qualidade da água (Capítulo 2)
Determinar a importância das variáveis ambientais na estruturação da comunidade defitoplâncton nos Tipos de albufeiras estudadas a diferentes escalas espaciais (geográfica, regional e local) e temporais (estações do ano, anos) (Capítulo 3)
Determinar, como proposto pela DQA, o grau de perturbação das diversas albufeiras, ao longo do tempo, através da comparação com os locais de referência para cada um dos Tipos determinados (Capítulo 4)
Desenvolver um modelo Estocástico Dinâmico (StDM), baseado numa abordagem multi escala,para prever o estado ecológico de albufeiras Mediterrâneas face a alterações de uso do solo nas respectivas bacias hidrográficas. Neste contexto, a bacia do Douro foi utilizada para testar e validar o modelo desenvolvido (Capítulo 5), assim como avaliar a sua performance na previsão de alteração da qualidade da água de uma albufeira, nomeadamente ao nível ambiental e biológico (fitoplâncton), face a expectáveis cenários espaciais de alteração de uso do solo (Capítulo 6).
Os resultados das diferentes abordagens foram consistentes na definição da tipologia das albufeiras portuguesas estudadas, assim como nos gradientes de poluição observados, que de algum modo parecem reflectir a degradação associada à conversão de áreas agro florestais em áreas ndustriais ou semi urbanas. Assim, foi possível identificar dois Tipos de massas de água com características hidromorfológicas, químicas e biológicas distintas, nomeadamente com comunidades fitoplântonicas específicas:
Tipo 1, albufeiras localizadas nos rios principais (Douro e Tejo) caracterizadas por elevadas concentrações de nutrientes e minerais. Este Tipo de albufeira “fio de água”, assemelha se muito mais a um sistema lótico do que a um sistema lêntico, apresentando tempos de residência baixos (dias), boa mistura e uma relativa elevada velocidade da corrente, nunca ou muito raramente ocorre estratificação. Em geral, situam se em áreas densamente povoadas, industriais ou agrícolas sujeitas a elevados inputs de matéria orgânica e descargas industriais.
Tipo 2, verdadeiros reservatórios, profundos e situados a altitudes elevadas. Geralmente, encontram se localizadas nos tributários e apresentam elevados tempos de residência (semanas a meses). Consequentemente, são fortemente afectados por fenómenos de estratificação.
Foi possível, determinar as comunidades fitoplânctonicas características de cada um dos Tipos de albufeiras referidos. Para ambos os tipos de sistemas regulados, foi também possível estabelecer os taxa característicos dos locais perturbados e dos locais menos perturbados ou de referência. Esta caracterização é um pré requisito essencial para o desenvolvimento de um processo de avaliação de acordo com a DQA, dado que a avaliação deve efectuar se através da comparação da composição de espécies actual com a que estaria presente em condições de referência.
Os resultados relativos à importância das escalas local e regional na estrutura e composição do fitoplâncton vieram corroborar estudos anteriores, reflectindo a importância do habitat e da paisagem nos ecossistemas lênticos. Estes resultados parecem demonstrar que o fitoplâncton pode ser um bom indicador ecológico na avaliação holística dos efeitos de pressões cumulativas ou multi escala, podendo vir a ser integrado no futuro, a nível regional ou mundial, na monitorização de albufeiras.
Relativamente ao modelo Estocástico-Dinânmico (StDM) desenvolvido, de uma maneira geral os resultados foram encorajadores dado que parecem demonstrar a consistência desta ferramenta em captar a dinâmica ambiental aleatória das métricas seleccionadas face a cenários espaciais expectáveis. Este tipo de abordagem holística pode eventualmente facilitar o ordenamento destas massas de água assim como a tomada de decisão segundo as exigências da DQA.
Globalmente, as metodologias desenvolvidas nesta tese poderão contribuir para a implementação da DQA em Portugal, especialmente na avaliação do estado ecológico, fornecendo novas ferramentas para a avaliação da integridade ecológica de sistemas lênticos, e pretende ainda contribuir para uma maior compreensão das alterações estruturais e funcionais que ocorrem nos sistemas aquáticos portugueses devido a pressões antropogénicas.
Worldwide aquatic ecosystems have been impacted by broad scale environental pressuressuch as agriculture, point and non point source pollution and land use changes overlapping in space and time, leading to the disruption of the structure and functioning of these systems. In face of this global change, declines in environmental quality of rivers respective and reservoirs are of increasing concern. This has lead to an increasing search for new technologies for the monitoring of reservoirs to establish priorities of conservation, protection and restoration to achieve the Maximun Ecological Potencial of these waterbodies in the context, the objective of this thesis was to develop new tools, supported by multivariate statistical analyses and modelling methodologies, which can be applied in assessing the ecological status of Mediterranean reservoirs, in the scope of the Water Framework Directive (WFD). This work intended to design integrated methodologies to capture the aquatic ecosystems complexity through a multi scale approach, in order to develop and understand the local and regional mechanisms that operate in reservoirs to better understand the occurring changes in the structure and functioning of this systems several ecosystem components (e.g. hydromorphological, physical, chemical and biological) and several disturbance factors (e.g. land use changes, hydrometric variations, point and non point source pollution, etc.) were incorporated, at different spatial and temporal scales of analysis the thesis was structured into seven chapters based in the analysis of extensive data bases, namely long term data bases collected in the field by the Laboratory of Environmental and Applied Chemistry (LABELEC) managed by the Portuguese Electricity Group (EDP), in five different Portuguese hydrographic regions (Lima, Cavado and Ave, Douro, Mondego and Tagus catchment), through a period of nine years (1996 to 2004) the major objectives of this thesis were: To establish the typology and the Type-specific reference condition of the portuguese Hydroelectric reservoirs based on biotic and abiotic quality elements, namely phytoplankton as Water quality indicator, through a multi scale approach. To determine the importance of environmental variables at different spatial (geographical,Regional and local) and time scales (seasons, years) on the phytoplankton community structure of the studied reservoirs Types. To determine, overtime, the degree of impairment ofthese reservoirs by contrasting it with a reference site, as proposed by the WFD. To develop a modeling multi scale approach, based on an holistic Stochastic Dynamic Methodology (StDM), in order to predict the ecological status tendencies in Mediterranean reservoirs as a response to land use changes in the respective watersheds. Therefore, the Douro’s basin was used to test and validate the StDM model, as well as evaluate the StDM performance in capturing how expected changes at land use level scenarios will alter the Reservoir water quality, namely at physicochemical and phytoplankton levels. The results of the different approaches were consistent in the typology defined for the Portuguese reservoirs, as well as in the observed pollution gradients, which in some extend reflected the degradation associated to the conversion of the agroforestry areas into industrialized and semi Urban areas. Therefore, it was possible to identify two types of dammed water bodies which were characterized by different hydromorphological features, water chemistry characteristics and by a specific phytoplankton taxa composition: Type 1 represents lowland reservoirs located in the main rivers (Douro and Tagus) characterized by higher concentrations of nutrients and water mineral content. This “riverine reservoirs”, resemble more a river than a lake, with short hydraulic retention times, good mixing and relative high water velocities, never or rarely affected by stratification phenomena. In general, is located in densely populated, industrialized or agricultural areas, receiving high inputs of organic matter and industrial discharge. Type 2 represents deeper high altitude “artificial lake reservoirs”, largely located in tributaries, with a high residence time, with longer water storage and release cycles operating under seasonal influence, strongly affected by stratification phenomena.It was possible to assign characteristic phytoplankton taxa assemblages to each type of reservoir. For Both regulated systems types, was also possible to establish he characteristic taxa of disturbed and Less or non disturbed sites. Such ascription is an essential prerequisite for the development of an Assessment procedure according to the WFD, where the assessment should be done by comparing The actual species composition to the one that would be present under reference conditions. Our findings of the importance of local and regional scale factors on phytoplankton community structure lend support to earlier studies, reflecting the importance of habitat and large scale (landscape) factors on reservoir ecosystems and demonstrate that Phytoplankton could be a good ecological indicator for multi scale and cumulative disturbance effects with a view to integrate future Worldwide monitoring in reservoirs. Regarding the developed modelling multi scale approach (StDM), the overall results were encouraging since they seem to demonstrate the tool reliability in capturing the stochastic environmental dynamics of the selected metrics facing spatial explicit scenarios. The ultimate goal of this approach was to couple monitoring assessment and the described modeling techniques to ease management and decision making regarding the requirements of the WFD. Overall, the methodologies presented in this thesis could contribute to the implementation of the WFD in Portugal, with regard specifically to the evaluation of the ecological status, providing new Tools for the ecological integrity assessment of lentic waters, and pretend to contribute to a larger Understanding of the structural and functional human induced alterations that occur in Portuguese aquatic ecosystems.
Worldwide aquatic ecosystems have been impacted by broad scale environental pressuressuch as agriculture, point and non point source pollution and land use changes overlapping in space and time, leading to the disruption of the structure and functioning of these systems. In face of this global change, declines in environmental quality of rivers respective and reservoirs are of increasing concern. This has lead to an increasing search for new technologies for the monitoring of reservoirs to establish priorities of conservation, protection and restoration to achieve the Maximun Ecological Potencial of these waterbodies in the context, the objective of this thesis was to develop new tools, supported by multivariate statistical analyses and modelling methodologies, which can be applied in assessing the ecological status of Mediterranean reservoirs, in the scope of the Water Framework Directive (WFD). This work intended to design integrated methodologies to capture the aquatic ecosystems complexity through a multi scale approach, in order to develop and understand the local and regional mechanisms that operate in reservoirs to better understand the occurring changes in the structure and functioning of this systems several ecosystem components (e.g. hydromorphological, physical, chemical and biological) and several disturbance factors (e.g. land use changes, hydrometric variations, point and non point source pollution, etc.) were incorporated, at different spatial and temporal scales of analysis the thesis was structured into seven chapters based in the analysis of extensive data bases, namely long term data bases collected in the field by the Laboratory of Environmental and Applied Chemistry (LABELEC) managed by the Portuguese Electricity Group (EDP), in five different Portuguese hydrographic regions (Lima, Cavado and Ave, Douro, Mondego and Tagus catchment), through a period of nine years (1996 to 2004) the major objectives of this thesis were: To establish the typology and the Type-specific reference condition of the portuguese Hydroelectric reservoirs based on biotic and abiotic quality elements, namely phytoplankton as Water quality indicator, through a multi scale approach. To determine the importance of environmental variables at different spatial (geographical,Regional and local) and time scales (seasons, years) on the phytoplankton community structure of the studied reservoirs Types. To determine, overtime, the degree of impairment ofthese reservoirs by contrasting it with a reference site, as proposed by the WFD. To develop a modeling multi scale approach, based on an holistic Stochastic Dynamic Methodology (StDM), in order to predict the ecological status tendencies in Mediterranean reservoirs as a response to land use changes in the respective watersheds. Therefore, the Douro’s basin was used to test and validate the StDM model, as well as evaluate the StDM performance in capturing how expected changes at land use level scenarios will alter the Reservoir water quality, namely at physicochemical and phytoplankton levels. The results of the different approaches were consistent in the typology defined for the Portuguese reservoirs, as well as in the observed pollution gradients, which in some extend reflected the degradation associated to the conversion of the agroforestry areas into industrialized and semi Urban areas. Therefore, it was possible to identify two types of dammed water bodies which were characterized by different hydromorphological features, water chemistry characteristics and by a specific phytoplankton taxa composition: Type 1 represents lowland reservoirs located in the main rivers (Douro and Tagus) characterized by higher concentrations of nutrients and water mineral content. This “riverine reservoirs”, resemble more a river than a lake, with short hydraulic retention times, good mixing and relative high water velocities, never or rarely affected by stratification phenomena. In general, is located in densely populated, industrialized or agricultural areas, receiving high inputs of organic matter and industrial discharge. Type 2 represents deeper high altitude “artificial lake reservoirs”, largely located in tributaries, with a high residence time, with longer water storage and release cycles operating under seasonal influence, strongly affected by stratification phenomena.It was possible to assign characteristic phytoplankton taxa assemblages to each type of reservoir. For Both regulated systems types, was also possible to establish he characteristic taxa of disturbed and Less or non disturbed sites. Such ascription is an essential prerequisite for the development of an Assessment procedure according to the WFD, where the assessment should be done by comparing The actual species composition to the one that would be present under reference conditions. Our findings of the importance of local and regional scale factors on phytoplankton community structure lend support to earlier studies, reflecting the importance of habitat and large scale (landscape) factors on reservoir ecosystems and demonstrate that Phytoplankton could be a good ecological indicator for multi scale and cumulative disturbance effects with a view to integrate future Worldwide monitoring in reservoirs. Regarding the developed modelling multi scale approach (StDM), the overall results were encouraging since they seem to demonstrate the tool reliability in capturing the stochastic environmental dynamics of the selected metrics facing spatial explicit scenarios. The ultimate goal of this approach was to couple monitoring assessment and the described modeling techniques to ease management and decision making regarding the requirements of the WFD. Overall, the methodologies presented in this thesis could contribute to the implementation of the WFD in Portugal, with regard specifically to the evaluation of the ecological status, providing new Tools for the ecological integrity assessment of lentic waters, and pretend to contribute to a larger Understanding of the structural and functional human induced alterations that occur in Portuguese aquatic ecosystems.
Descrição
Tese de Doutoramento em Ciências do Ambiente
Palavras-chave
Reservatórios (Albufeiras) , Ecossistemas - - Condições ecológicas , Análise multivariada , Directiva Quadro de Água (DQA) , Reservoirs , Ecological condition , Multivariate analysis , Water Framework Directive