Zooplancton de três piscinas biológicas cujas macrófitas apresentam diferentes graus de desenvolvimento

As piscinas biológicas são pequenos lagos construídos onde são recriadas as condições ecológicas que ocorrem em ecossistemas lacustres naturais. Ao contrário das piscinas convencionais a depuração da água é realizada por filtros biológicos de macrófitas e nenhum produto químico é adicionado. À semelhança dos lagos naturais, para além das plantas aquáticas, ocorrem também organismos do fito e do zooplâncton, macro-invertebrados e alguns vertebrados, como é o caso dos anfíbios e dos répteis. Em regiões com verões secos e quentes pode ocorrer o desenvolvimento excessivo de algas filamentosas e fitoplanctónicas. Este facto leva à diminuição do valor estético e recreativo das piscinas afectadas. Uma das medidas que poderá contribuir para a resolução deste problema será criar condições que favoreçam o incremento das espécies herbívoras do zooplancton. Com este objectivo, foi caracterizada, através de amostragens realizadas em Fevereiro, Abril e Junho de 2007, a comunidade zooplanctónica de três piscinas biológicas: R, G e S cujas macrófitas apresentavam graus de desenvolvimento diferenciados

Landscape runoff, precipitation variation and reservoir limnology

Landscape runoff potential impact on reservoir limnology was indirectly evaluated by assessing the effect of precipitation variation on several water quality parameters, on Anabaena (Cyanophyta) and crustacean zooplankton abundances. The obtained results showed that total phosphorus increased with strong precipitation events whereas water transparency presented an opposite trend. Wet periods followed by long dry periods favored Anabaena dominance, which induced an accentuated decreasing on all crustacean zooplankton species abundance. Therefore, in a climate changing scenario these data are crucial to monitor and predict the effect of landscape changes on aquatic ecosystem integrity and ultimately in water quality

Plano nacional de barragens com elevado potencial hidroelectrico: dúvidas e questões

O Plano Nacional de Barragens com Elevado Potencial Hidroeléctrico (PNBEPH) foi lançado em 2007 e tem como meta atingir uma capacidade instalada hidroeléctrica nacional superior a 7000 MW em 2020, As 10 novas barragens que foram consideradas neste plano irão localizar-se cm rios que ainda possuem uma elevada integridade ecológica, De acordo com a Diretiva Quadro da Água, até 2015 as águas superficiais de todos os estados-membros deverão atingir um bom estado ecológico, Embora a Diretiva permita a criação de novas barragens os estados-membros deverão evitar tomar ações que ameacem os seus objectivos. Fazendo um balanço entre os custos da degradação do património natural/cultural, os ganhos em termos de produção hidroeléctrica, os custos de construção e de manutenção destes empreendimentos, surgem duas grandes questões: Será que a implementação do PNBEPH c uma das soluções para a resolução dos problemas energéticos ou será uma nova fonte de problemas para o país? Será que os promotores tiveram em conta o cenário de alterações climáticas, a correta minimização de impactes c a necessária alteração do paradigma energético português

Avaliação da condição actual das piscinas biológicas de Rossas, Guilhofrei e Sobradelo

No presente relatório é caracterizado o estado de três piscinas biológicas. Prstação de Serviços à Empresa Bio Piscinas - Piscinas biológicas e sistemas ecológicos de tratamento de água, Lda

Landscape runoff, precipitation variation and reservoir limnology

Landscape runoff potential impact on reservoir limnology was indirectly evaluated by assessing the effect of precipitation variation on several water quality parameters, on Anabaena (Cyanophyta) and crustacean zooplankton abundances. The obtained results showed that total phosphorus increased with strong precipitation events whereas water transparency presented an opposite trend. Wet periods followed by long dry periods favored Anabaena dominance, which induced an accentuated decreasing on all crustacean zooplankton species abundance. Therefore, in a climate changing scenario these data are crucial to monitor and predict the effect of landscape changes on aquatic ecosystem integrity and ultimately in water quality

Reservoirs: mirrors of the surrounding landscape?

To assess in what extent the environmental quality of aquatic systems reflect landscape features several water quality parameters were determined in two reservoirs. Concomitantly, the surrounding landscape was characterized and the existing potential sources of phosphorous and nitrogen runoff were identified and when possible estimated. Located in a mountainous area with negligible direct human influence, it was expected to find lower amounts of suspended organic matter and nutrients in Serra Serrada Reservoir. Water level fluctuations caused by intensive human water use, grazing and frequent land fires in the surrounding landscape can explain the unexpected high values of the mentioned parameters. In Azibo Reservoir the factors with greatest influence on water parameters seem to be allochthonous sources of nutrients originated from agriculture and grazing in the catchment area and recreational activities. However, in this particular case the potential sources of nutrients could have been minimized by the patchy structure of the surrounding landscape

Distinct age and landscape influence on two reservoirs under the same climate

With the purpose of finding out whether different landscape occupation could affect water quality in two reservoirs of distinct age and subjected to the same climatic influence, several factors were investigated in a study lasting from January 2000 till December 2001. Total phosphorus, orthophosphate, chlorophyll a concentrations and water colour were determined monthly in winter and biweekly in summer, in two reservoirs located in the Portuguese part of River Douro catchment. Complementarily, variables such as nitrate, ammonium ion and ammonia gas, as well as water temperature, dissolved oxygen, conductivity, and transparency were measured. Trophic state of both reservoirs was assessed by computation of Carlson’s Trophic State Index. The potential allochthonous sources of phosphorus and nitrogen to both reservoirs were identified and estimated. Differences between reservoirs were found for conductivity, water temperature, transparency and water colour. According to Carlson’s Trophic State Index both reservoirs were classified as meso-eutrophic from winter to the beginning of summer, and as eutrophic from this period onwards. Intrinsic factors such as age of reservoir, organic matter inputs from decomposition of flooded terrestrial vegetation and exposure of littoral sediments to cycles of drying and wetting, as well as extrinsic factors such as grazing and frequent land fires, can explain the trophic state of S. Serrada Reservoir. Allochthonous sources of nutrients originated from agriculture and grazing in the catchment area, and recreational activities in the reservoir probably are the factors with greatest influence on Azibo Reservoir trophic state. Based upon the obtained data, management measures are suggested to prevent further eutrophication and water quality degradation in both reservoirs

What factors affect the pelagic cladocerans of the meso-eutrophic Azibo Reservoir?

The assemblage patterns of pelagic Cladocera species were investigated in a meso-eutrophic reservoir from January 2000 to December 2002. Trends of environmental factors (water temperature, conductivity, pH, and nutrient concentrations), as well as of biotic factors (availability of potentially edible phytoplankton and densities of herbivorous and carnivorous copepods) were assessed. Zooplankton community was dominated by Cladocera and Copepoda. Assemblage patterns for Cladocera were identified by performing a cluster analysis on abundance data of the dominant species: Daphnia longispina, Ceriodaphnia pulchella, Bosmina longirostris and Diaphanosoma brachyurum. In winter and spring, Daphnia was dominant. In early summer and end of autumn, Ceriodaphnia and Daphnia coexisted. During summer, Ceriodaphnia was dominant and coexisted with Diaphanosoma. Bosmina was present in low densities during the whole study period. Cladoceran populations exhibited non-synchronous peaks of abundance, evidencing different ecological optima. Temperature seemed to be the main structuring factor of this assemblage. The way biotic interactions influenced pelagic cladoceran assemblage in this reservoir was not clear and needs further research.Project Praxis XXI/C/BIA/11012/98) and a doctoral fellowship to AMG (4/5.3/PRODEP/2000).FCT - Project Praxis XXI/C/BIA/11012/98) and 4/5.3/PRODEP/200

Do distinct water chemistry, reservoir age and disturbance make any difference on phosphatase activity?

Alkaline phosphatase activity was assessed concomitantly with total phosphorus, orthophosphate and phosphomonoester concentrations in two meso-eutrophic reservoirs with distinct age and subjected to different kinds of environmental influence. Differences in conductivity, temperature and pH were found. However, during the study period alkaline phosphatase activity was similar in both reservoirs. Water colour was higher in S. Serrada Reservoir. This fact can be related to (1) reservoir age (2) high internal disturbance (3) large imputs of allochthonous detritus, resulting from the combined effect of grazing, fire and catchment slope. Despite the high water colour recorded in S. Serrada, alkaline phosphatase activity was apparently not inactivated by humic substances. Besides, the obtained results demonstrated that hydrolysis of phosphomonoesters by alkaline phosphatase was not important for orthophosphate regeneration in these reservoirs. Probably orthophosphate was always available to biota. In fact, in the experiments based on Selenastrum capricornutum Printz algal test, similar phytoplankton growth responses were obtained for different phosphorus concentrations. Thus, these results seem to indicate that phosphorus was not a limiting nutrient in either reservoir. Although phosphatase activity was significantly correlated with some phytoplankton genera in both reservoirs, no significant correlations were found between enzyme activity and chlorophyll-a. Significant correlations between phosphatase activity and crustacean zooplankton were only recorded in S. Serrada. In spite of these results there was some indication that the main source of phosphatase might have been bacteria involved in decomposition processes instead of phyto- and zooplankton taxa.FCT - PRAXIS XXI/C/BIA/11012/98 4/5.3/PRODEP/200

Efeitos da intensidade do uso da água e das práticas de gestão na limnologia de três albufeiras localizadas na bacia do Douro, NE Portugal

da idade desta albufeira (Geraldes & Boavida 2004). Peneiiiireiiiiro A separação (análise MDS) desta albufeira das outras, antes do seu esvaziamento total, deve-se ao facto de apresentar concentrações muito mais elevadas de TP e de SRP. Estes valores estão provavelmente relacionados com as práticas agrícolas que ocorrem nas zonas circundantes. Por outro lado, tanto a área da albufeira como a da sua bacia são muito pequenas. Este facto faz com que as escorrências provenientes das áreas agrícolas tenham um impacto mais acentuado na qualidade da água. Em consequência da ocorrência de um bloom de Anabaena e de Microcystis esta albufeira foi completamente esvaziada e a camada superior de sedimentos foi removida com o objectivo de reduzir a disponibilidade de nutrientes e assim, diminuir as densidades destas cianobactérias. Após o seu reenchimento as concentrações de nutrientes, como seria de esperar baixaram (e.g. Harper 1992). Os valores destes parâmetros aproximaram-se assim dos das outras albufeiras (ver análise MDS). No entanto, as densidades de Anabaena permaneceram relativamente elevadas. No que diz respeito ao zooplâncton apenas se verificou um aumento das densidades dos Rotífera à semelhança do que foi observado por outros autores em sistemas que foram também sujeitos a processos de esvaziamento/reenchimento (e.g. Crispim & Boavida 1993)