Browsing by Author "Condinho, S."
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- Adenylic-derived indices and reburying time as indicators of the effects of dredging-induced stress on the clam Spisula solidaPublication . Teodosio, Maria; Araújo Amaral, Ana Margarida; Condinho, S.; Alves, Filipe; Regala, J.; Gaspar, M.; Chícharo, LuísLittle attention has been given to the behavioural and physiological effects of dredging on clams. The response of the clam Spisula solida under stress imposed by dredging activity is analysed in terms of reburial time and two acute indices: AEC (adenylic energetic charge) and ATP per milligram dry weight. Stress on undersized (<25 mm) S. solida, due to habitat disturbance by dredging itself and subsequent aerial exposure was measured with in situ studies during September 1999 at Vilamoura, a bivalve sandy ground, off the southern coast of Portugal. The study showed significant increases in reburial time and a decrease in adenylic-derived indices of stressed bivalves compared with in situ control bivalves monitored by SCUBA divers. It was concluded that the stress caused by dredging affects the behavioural and physiological responses of S. solida. Moreover, the reburial time is an easy and valuable indicator of stress levels in the studied clam.
- Chronic effects of dredging-induced stress on the clam (Spisula solida): nucleic acid and lipid compositionPublication . Chicharo, Alexandra; Chícharo, Luís; Araújo Amaral, Ana Margarida; Condinho, S.; Gaspar, M.Responses of the clam Spisula solida to stress imposed by dredging were analyzed in terms of changes in chronic indices of biochemical conditions (RNA/DNA ratio and neutral/polar (N/P) lipid ratio). Cumulative stress on undersized (<25 mm) S. solida from repeated habitat disturbance by dredging was simulated in the laboratory and measured with in situ studies off the southern coast of Portugal, in April and July 1999. Laboratory simulations on undersized bivalves indicated decreases in RNA/DNA and N/P lipid ratios. Responses were sublethal; however, even though survival was not directly threatened, decreases in condition suggest that bivalves are more susceptible to predation when they have been left in the seabed after the dredging activity. Moreover, the in situ study revealed that this effect could be especially critical during spawning.
- 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.