Browsing by Author "Chícharo, Luís"
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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.
- Algal cover and sea urchin spatial distribution at Madeira Island (NE Atlantic)Publication . Alves, Filipe; Chícharo, Luís; Serrão, Ester; Abreu, A. D.This study describes sea urchin spatial distribution in relation to environmental factors, and the relationship between Diadema antillarum density and algal abundance. Twenty-three transects around Madeira Island were surveyed by scuba divers, and sea urchin density and algal cover were determined in situ. Sampling sites along these transects were characterised in terms of distance from the tide line, water depth, substratum type, bottom declivity and water turbulence. Diadema antillarum was the dominant sea urchin species. Paracentrotus lividus and Arbacia lixula occurred at shallower depths (2-6 m), contrasting with the distribution of Sphaerechinus granularis, which occurs among D. antillarum (4-20 m). Surveys found two alternative types of communities on rocky shores: 1) a community with high algal cover and low numbers of sea urchins, along the north and south-west coasts and; 2) a community with little algal cover and high densities of sea urchins, along the south-east coast. Macroalgal cover and D. antillarum densities were inversely correlated (adjusted R2=75.6%; n = 429; p< 0.05). The results showed that water turbulence was the most important factor limiting the distribution of D. antillarum on rocky substrates. We propose a multiple non-linear regression model (using backward stepwise analysis) to explain D. antillarum abundance on the rocky shores: D. antillarum/m2 (??)= 0.121 - 0.209 distance from shore (in m) (??) + 2.052 water depth (in m) (??) - 1.778 water turbulence level (??) - 0.007 water turbulence level4 (??); where ?? indicates data are square-root transformed (adjusted R2 = 60.99%; n = 454; p< 0.05).
- Alien species in the Guadiana Estuary (SE-Portugal/SW-Spain): Blackfordia virginica (Cnidaria, Hydrozoa) and Palaemon macrodactylus (Crustacea, Decapoda): potential impacts and mitigation measuresPublication . Teodosio, Maria; Leitão, Tânia; Range, Pedro; Gutierrez, Cristina; Morales, Jesus; Morais, P.; Chícharo, LuísThe cnidarian Blackfordia virginica and the adult of the caridean prawn, Palaemon macrodactylus are first recorded from the Guadiana Estuary. The habitats and environmental conditions under which these species were found are described and the potential impacts and mitigation measures for their introduction are discussed. The first observations of adults of these species were made in July 2008, at the transitional zone of the estuary (brackish area). Most samples taken in the middle-estuary were characterized by large densities of B. virginica (> 100 individuals 100 m-3), while P. macrodactylus was recorded in much smaller densities (<0.01 individuals m-2). Despite a comprehensive survey of invertebrates done between 1999 and 2003, neither of these species was previously detected in the Guadiana estuary. These observations may, therefore, coincide with the introduction of these species to the Guadiana estuary. Small planktonic crustaceans are generally described as the main food items for B. virginica. Our results show that the presence of the medusa was usually associated with a reduction of densities of all zooplanktonic organisms, including eggs of Engraulis encrasicolus. The reduction of planktonic biomass could have severe implications for organisms at upper trophic levels, such as E. encrasicolus, which use the Guadiana estuary as a nursery area and feed mostly on small planktonic crustaceans. Moreover, the potential consumption of eggs by B. virginica could potentially increase the impact on the nursery function of the estuary. The other alien species detected, P. macrodactylus, appears to be a strong invader, able to colonise a wide geographical range. It has a strong osmoregulatory capacity, and is known to inhabit a wide range of salinities, particularly if compared to similar native species (Crangon crangon and Palaemon longirostris). There is clear potential for the occurrence of competition for food between P. macrodactylus and the native prawn, due to dietary overlapping. The Guadiana estuary is under Mediterranean climate influence and is expected to be strongly impacted by climatic changes in the next decades. Other threat-factors are also present, such as increasing regulation by dams, the construction of new harbors, and increase shipping activity. It is important, therefore, to study the impact of these new invasions in this estuary and, based on the ecohydrology approach, propose mitigations measures to be applied in this system and other similar ecosystems worldwide.
- An analysis of the impacts of climatic variability and hydrology on the coastal fisheries, Engraulis encrasicolus and Sepia officinalis, of PortugalPublication . Ullah, Hadayet; Miguel de Sousa Leitão, Francisco; Baptista, Vânia; Chícharo, LuísThe notion that climate change may impact coastal fish production suggests a need to understand how climatic variables may influence fish catches at different time scales. Evidence suggests that the effect of climatic variability and fishing effort on landed catches (as proxy of fish abundance) may vary at the regional scale. This study aims to assess the sensibility of two commercial species with a short life cycle (Engraulis encrasicolus and Sepia officinalis) to climatic and fisheries effects across different regions of the coast of Portugal: northwestern, southwestern and southern Portugal. The effect of environmental explanatory variables, i.e. NAO index, sea surface temperature (SST), upwelling (UPW) index, river discharge, wind magnitude (WmaG), wind direction (Wdir), and fishing variables (fishing effort) on catch rates time series were studied between 1989 and 2009. The sensibility of the species studied to climatic variability differed among regions and were explained by different climatic variables. River discharge had a significant effect on catch rates of the two species, region independently. However, wind driven phenomenon and UPW were the variables that better explained the observed fishing trends across the three regions. Changes in catch rate trends among the studied regions, at a given time, were mostly associated with the reproduction periods of the species. Therefore, regional analyses will significantly contribute to a better understanding of the relationship between climate change and coastal fisheries, aiming to improve integrated coastal zone management.
- An ecohydrology model of the Guadiana Estuary (South Portugal)Publication . Wolanski, Eric; Chícharo, Luís; Teodosio, Maria; Morais, P.A 1-D ecohydrology model is proposed that integrates physical, chemical and biological processes in the Guadiana Estuary during low flow conditions and that predicts the ecosystem health as determined by the following variables: river discharge, nutrients, suspended particulate matter, phytoplankton, zooplankton, bivalves, zooplanktivorous fish and carnivorous/omnivorous fish. Low flow conditions prevail now that the Alqueva dam has been constructed. The ecological sub-model is based on the non-linear Lotka-Volterra equation. The model is successful in capturing the observations of along-river changes in these variables. It suggests that both bottom-up and top-down ecological processes control the Guadiana Estuary ecosystem health. A number of sensitivity tests show that the model is robust and can be used to predict e within likely error bounds provided by the sensitivity tests e the consequences on the estuary ecosystem health of human activities throughout the river catchment, such as the irrigation farming downstream of the Alqueva dam, reclamation of the salt marshes by urban developments, and flow regulation by the Alqueva dam. The model suggests that the estuarine ecosystem health requires transient river floods and is compromised by flow regulation by the Alqueva dam. Remedial measures are thus necessary.
- Application and demonstration of the ecohydrology approach for the sustainable functioning of the Guadiana estuary (South Portugal)Publication . Chícharo, Luís; Ben-Hamadou, Radhouan; Araújo Amaral, Ana Margarida; Range, Pedro; Mateus, Carmen; Piló, David; Marques, Rute; Morais, P.; Teodosio, MariaThe implementation of the UNESCO demosite at the Guadiana estuary represents an excellent opportunity to demonstrate how to adapt, mitigate and restore functioning of estuaries and coastal areas impacted by dams and climatic changes, using the Ecohydrology approach. Worldwide estuaries are suffering similar anthropogenic impacts that affect ecosystem functioning, biodiversity and resources. Therefore, the mesocosms experiments at the Guadiana Ecohydrology demosite constitute a collection of case studies, whose results can be used for testing solutions for the sustainable management of other estuarine systems. We applied the Ecohydrology concepts and methods to test: a) the usefulness of freshwater inflow pulses to regulate biodiversity and to control microalgal blooms , by regulating nutrient ratios and thus enhancing the bottom-up control of water quality; b) the usefulness of using the feeding ability of bivalve assemblages to control microalgal blooms (top-down control of water quality, and; c) the role of salt marsh plants (Salicornia ramosissima) to reduce excessive concentrations of nutrients and control estuarine water quality. Results show that the interplay between organisms (bivalves, plants) and hydrological factors is a key for improving water quality and sustaining biodiversity and the good ecological status of this estuarine ecosystem.
- Applying the ecohydrology approach to the Guadiana estuary and coastal areas: lessons learned from dam impacted ecosystemsPublication . Chícharo, Luís; Chicharo, AlexandraEcohydrology is a scientific concept applied to problem- solving in environmental issues. It recognises that the present practice of relying nearly exclusively on engineering fixes to solve environmental problems is failing to restore the aquatic environment to a level that can sustain the quality of life that people are demanding. Ecohydrology is based on the ability of science to quantify and explain the relationships between hy- drological processes and biotic dynamics at a catchment scale and to manipulate these processes to increase the robustness of the aquatic system and thus its ability to cope with human- induced stresses. The concept was developed by the UNESCO International Hydrologic Programme (IHP) and the Man and Biosphere Programme (MAB).
- Are submarine groundwater discharges affecting the structure and physiological status of rocky intertidal communities?Publication . Piló, David; Barbosa, Ana B.; Teodosio, Maria; Encarnação, J.; Miguel de Sousa Leitão, Francisco; Range, Pedro; Krug, Lilian; Cruz, J.; Chícharo, LuísThis study evaluated the impacts of submarine groundwater discharges (SGD) on a rocky intertidal community of South Portugal, during April-November 2011. Chlorophyll-a concentration was higher at the SGD site in respect to the Reference site. Epibenthic community structure differed between sites, with an increase in Chthamalus spp. and a decrease in macroalgae coverage at the SGD site. The abundance and body size of Mytilus galloprovincialis were consistently higher at the SGD site. During mid-spring, under potentially higher SGD and less favorable conditions for coastal phytoplankton, the ecophysiological condition of M. galloprovincialis and G. umbilicalis was also higher at the SGD site. These beneficial effects on filter-feeders and herbivores probably resulted from local increases in prey availability, supported by SGD-driven nutrient inputs. Conversely, P. depressa was not favoured by SGD, probably due to a lower dependency on algae as food. The analysis of epibenthic community structure and ecophysiological condition represents a promising approach to disentangle the ecological impacts of SGD on intertidal ecosystems.
- Are tidal lagoons ecologically relevant to larval recruitment of small pelagic fish? An approach using nutritional condition and growth ratePublication . Chicharo, Maria Alexandra; Araújo Amaral, Ana Margarida; Faria, Ana Margarida da Silva; Morais, R.; Mendes, C.; Piló, David; Ben-Hamadou, Radhouan; Chícharo, LuísThere are numerous studies dealing with larvae of Small Pelagic Fish (SPF), but only a few have actually addressed advanced larval phases. Temperate coastal lagoons are particularly understudied, due to the absence of standard method to capture advanced larval fish in these near shore shallow habitats. Accordingly, this study aims to describe abundances, nutritional condition and in situ growth of postflexion (SPF) from the Ria Formosa, a tidal coastal lagoon in southern Portugal. The nutritional condition and in situ growth were determined through cohort analysis and standardized RNA:DNA ratio (sRD), complemented with feeding incidence (gut content) and fatty acids (FAs, trophic biomarkers) of postflexion larvae sampled sequentially with light traps, from spring 2005 to summer 2006. Simultaneously, environmental parameters such as water temperature, salinity, dissolved oxygen and chlorophyll a were measured. Post-larvae of SPF were captured through the year in important numbers. The dominant species were Sardina pilchardus (50.7%), Engraulis encrasicolus and Atherina presbyter (11.4%). These results are distinct from those based on adult/juvenile surveys or early planktonic phases in the Ria Formosa where clupeiformes were occasionally reported. Sardines were captured mainly in winter, spring and early summer and anchovies mainly during summer and autumn. Sand smelt, a resident species, was present throughout the year. In the early summer, the three species were present and during this period some diet overlapping occurred, the feeding incidence of the clupeiformes was very low, but atherinids always exhibited full guts reflecting the different gut morphology or indicating different lifecycle strategies. The bulk of the diet was mollusks, crustaceans and appendicularians, for sand smelts, sardines and anchovies, respectively. The results of FA analyses showed some contribution of phytoplankton to SPF in the area. All SPF exhibited higher condition (sRD) and growth rates in summer, which are explained by the adequate temperature and higher planktonic productivity. This is especially relevant because the successful development of postflexion larvae in these nursery areas largely determines the successful recruitment to adult fish populations.
- Calcification, growth and mortality of juvenile clams Ruditapes decussatus under increased pCO(2) and reduced pH: variable responses to ocean acidification at local scales?Publication . Range, Pedro; Chicharo, Alexandra Maria; Ben-Hamadou, Radhouan; Piló, David; Matias, Domitília; Joaquim, Sandra; Oliveira, A. P.; Chícharo, LuísWe investigated the effects of ocean acidification on juvenile clams Ruditapes decussatus (average shell length 10.24 mm) in a controlled CO2 perturbation experiment. The carbonate chemistry of seawater was manipulated by diffusing pure CO2, to attain two reduced pH levels (by −0.4 and −0.7 pH units), which were compared to unmanipulated seawater. After 75 days we found no differences among pH treatments in terms of net calcification, size or weight of the clams. The naturally elevated total alkalinity of local seawater probably contributed to buffer the effects of increased pCO2 and reduced pH. Marine organisms may, therefore, show diverse responses to ocean acidification at local scales, particularly in coastal, estuarine and transitional waters, where the physical–chemical characteristics of seawater are most variable. Mortality was significantly reduced in the acidified treatments. This trend was probably related to the occurrence of spontaneous spawning events in the control and intermediate acidification treatments. Spawning, which was unexpected due to the small size of the clams, was not observed for the pH −0.7 treatment, suggesting that the increased survival under acidified conditions may have been associated with a delay in the reproductive cycle of the clams. Future research about the impacts of ocean acidification on marine biodiversity should be extended to other types of biological and ecological processes, apart from biological calcification.