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- Toxicity risks linked to cyanobacteria blooms in southern Portugal reservoirsPublication . Caetano, Sandra; Reis, Margarida P.Cyanobacteria massive proliferation in freshwater ecosystems has become a relevant public health concern. The main objective of this study was to assess the toxicity risks linked to the proliferation of cyanobacteria in southern Portugal reservoirs, while alerting to the need to widen and strengthen the connection between environment and human health. This work also contributes to highlight the role of phytoplankton dynamics in the development of Cyanobacteria Hazard Algal Blooms (CyanoHABs). All addressed reservoirs revealed dominance of cyanobacteria in terms of abundance, exhibiting blooms, especially during the dry season. Following a global trend, these reservoirs exhibited CyanoHABs increase, with constant presence of toxigenic species which constitutes a threat to public health and often limits water use. From the perspective of future climate change, with expected worsening of the torrential hydrologic regime, increase in CyanoHABs occurrence is expected. Biogeographical expansion of exotic toxigenic cyanobacteria has begun in these reservoirs, also presenting public health risks, since their toxins are not regularly screened. This study includes the first notification of Cylindrospermopsis raciborskii in Alqueva reservoir, in similar abundances to those already detected by other authors in Southern Portugal reservoirs. Confirming invasive toxigenic species success in these waters. Even in oligotrophic reservoirs (Beliche), cyanobacteria prevail, indicating bottom-up factors are not always as important as assumed, whereby top-down factors must be further investigated. The development of ecological indices based on phytoplankton data should allow inderect inference about potential public health risks. Given its simplicity, the dominance index of potentially toxic cyanobacteria (PTCD) may constitute an option, when calibrated through its application to more systems. This work contributes to: (i) the understanding of cyanobacteria dynamics within phytoplankton, (ii) the acknowledgement of the hazards linked to their presence and (iii) constitutes a b
- Role of microbes in the Ria Formosa lagoonPublication . Galvão, Helena M.; Mendes, Pedro; Caetano, Sandra; Icely, John; Newton, AliceWith the development of epifluorescence microscopy and sensitive radioisotope techniques, high abundance and activity of microorganisms was observed in marine waters since 1970s and 1980s. These observations resulted in a new concept of rapid turn-over and recycling of organic matter through a ‘microbial loop’ (Azam et al., 1983; Azam, 1998). Figure 5.1 illustrates fluxes of material through the marine microbial loop. Main processes are C fixation by photosynthetic microorganisms (prokaryotic and eukaryotic) with exudation losses of Dissolved Organic Matter (DOM), which is incorporated by heterotrophic bacteria. Phagotrophic protists in turn graze both autotrophs and bacteria producing ‘sloppy feeding’ loss of DOM, which returns to the loop. DOM is remineralized by all microorganisms into Dissolved Inorganic Nutrients (DIN), which are taken up by autotrophic and heterotrophic microorganisms.
- 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.