Browsing by Author "Reis, Margarida P."
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- Cyanobacteria blooms in natural waters in Southern Portugal: a water management perspectivePublication . Galvão, Helena M.; Reis, Margarida P.; Valério, Elisabete; Domingues, Rita; Costa, Cristina; Lourenço, Dulce; Condinho, S.; Miguel, Rute; Barbosa, Ana B.; Gago, Conceição; Faria, Natália; Paulino, Sérgio; Pereira, PauloThis synthesis of 3 studies from 2 regions of southern Portugal (Alentejo and Algarve) was part of a workshop focusing on cyanobacteria held at the SAME 10. The first study monitored impacts of the large Alqueva dam on the Guadiana estuary since 1996, revealing changes in sediment load, nutrient regime and phytoplankton succession. Prior to dam construction, dense cyanobacterial blooms occurred in the upper estuary during summer and fall. After dam construction, chlorophyll concentration, phytoplankton diversity and abundances of cyanobacteria decreased, contrary to predictions. Mycrocystins remained at low levels in the seston and undetectable in water samples, except during summer 2003 when the particulate fraction contained 1 μg l–1, while chlorophyll concentrations and abundances of potentially toxic cyanobacteria remained low. Algarve reservoirs studied since 2001 revealed differences in phytoplankton dynamics. In the western mesotrophic reservoirs (Bravura and Funcho), 40 to 50% of surface samples contained cyanobacterial concentrations of ≥2000 cells ml–1, while over 80% of samples from the eastern oligotrophic reservoirs (Odeleite and Beliche) exceeded this value. Spring blooms were dominated by Oscillatoriales in Odeleite and Beliche and by Chroococcales in Bravura and Funcho. Bloom composition seemed to depend on water temperature and management strategies, while toxin concentrations reflected the increased biomass of toxic species. Finally, phytoplankton communities and microcystin production in 5 Alentejo freshwater reservoirs were studied from May to December 2005 and April to July 2006. Cyanobacterial blooms occurred, with varying intensities, not only during summer but also occasionally in winter. Microcystins were detected in 23% of the samples (n = 51), but without correlation with cyanobacterial biomass. Although Microcystis aeruginosa seemed to be the major producer of microcystins, other potentially toxic species were found. In summary, the varying pattern of cyanobacterial bloom occurrence and toxicity requires a systematic approach to monitoring programs for adequate risk assessment.
- Ecological tools for the management of cyanobacteria blooms in the Guadiana River watershed, Southwest IberiaPublication . Galvão, Helena M.; Reis, Margarida P.; Domingues, Rita B.; Caetano, Sandra; Mesquita, Sandra; Barbosa, Ana B.; Costa, Cristina; Vilchez, Carlos; Ribau Teixeira, MargaridaStrong water demand for irrigation, energy and drinking water production is responsible for an increasingly regulation of freshwater flow patterns and watersheds. In this context, the construction of dams allows water storage but seriously restricts freshwater flow downstream. Due to scarcity of freshwater resources, reservoir water management often promotes high hydraulic residence. This may cause strong impacts on biological components of aquatic ecosystems, influencing the development of cyanobacteria blooms and aggravating their harmful impacts.
- Modelação da qualidade microbiológica da água na Ria FormosaPublication . Venâncio, A.; Brito, Alberto M.; Martins, Flávio Augusto Bastos da Cruz; Reis, Margarida P.Este estudo integra-se numa avaliação hidrodinâmica e monitorização microbiológica da qualidade da água da Ria Formosa. A monitorização foi implementada pela DRAOT Algarve com a colaboração da EST, da FCMA e do IST. A metodologia utilizada consiste na aplicação de um modelo matemático para simulação das variáveis hidrodinâmicas e da qualidade da água. Utilizam-se como traçadores os coliformes fecais (CF), considerados indicadores de contaminação fecal pelo Dec-Lei 236/98 de 1 de Agosto, relativo à qualidade de águas do litoral e salobras para fins aquícolas- águas conquícolas. As águas da ria são usadas para cultura de diversas espécies conquícolas de bivalves. Estes são organismos que filtram e retêm no seu interior material particulado existente em suspensão na água tais como os CF entre outros microorganismos presentes na água. Para avaliar a concentração de coliformes nos bivalves e gastrópodes foi desenvolvido um modelo que simula a bioacumulação desta propriedade por parte do bivalve. Da sua aplicação permite classificar a Ria em várias classes conforme o estabelecido no Dec. Lei nº 293/98 de 18 de Setembro.