Browsing by Author "Range, Pedro"
Now showing 1 - 10 of 23
Results Per Page
Sort Options
- 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.
- 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.
- 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.
- 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.
- Effects of inter-annual freshwater inflow shifts on the community structure of estuarine decapodsPublication . Encarnação, João; Leitão, Tânia; Morais, P.; Piló, David; Range, Pedro; Chícharo, Luís; Chicharo, AlexandraThe objective of this study was to evaluate how inter-annual changes in freshwater inputs have affected the decapod assemblages in the Guadiana estuary. Three major areas in the estuary were sampled during the summer, in 2001 (high inflow year and before the filling of the Alqueva dam), in 2002 (low inflow and after filling of the Alqueva dam), and in 2008 and 2009 (low inflow and after consolidation of the impacts of the Alqueva dam). A significant increase in total decapod densities was recorded for the entire estuary, but especially in the upper estuary, after the closure of the dam in 2002. Changes in salinity, turbidity and temperature, which were mainly due to changes in freshwater input and climatic influence (North Atlantic Oscillation index), had an important influence on the structure of the decapod crustacean assemblages. The major conclusions of the study were that, following the construction of the Alqueva dam and regularization of the freshwater inflow, the decapod crustacean community in the Guadiana estuary changed and a shift of the dominant decapod species to upper zones of the estuary happened. These changes, and the presence of the non-native Palaemon macrodactylus in 2008 and 2009, further enhance the importance of estuarine monitoring studies to improve ecologists’ knowledge on distinguishing and understanding natural changes and anthropogenic impacts in the ecosystem.
- Effects of sea-water acidification on fertilization and larval development of the oyster Crassostrea gigasPublication . Barros, P.; Sobral, P.; Range, Pedro; Chícharo, Luís; Matias, DomitíliaOceans face a serious change to their natural biogeochemical cycle due to the rapid absorption of CO2 generated by human activities. Ocean acidification is the common term used to describe the decrease of seawater pH caused by the absorption of atmospheric CO2. To evaluate the effects of ocean acidification, we focused on the larval stage of bivalves, which produce a fragile calcareous skeletal structure, very sensitive to changes in seawater chemistry. In this context, we investigated sperm motility, fertilization rate and larval viability (survival, growth and abnormalities) of the Pacific oyster, Crassostrea gigas, a commercially important bivalve, in a controlled CO2 perturbation experiment. The carbonate chemistry of seawater was manipulated by diffusing pure CO2, to attain two reduced pH levels (ΔpH=−0.4 and ΔpH=−0.7) which were compared to unmanipulated seawater. The results show high sensitivity of C. gigas veliger larvae to low values of pH, as reflected by a decrease in survival and growth rates, as well as an increased frequency of prodissoconch abnormalities and protruding mantle. Moreover, results also show that sperm motility, fertilization rate, and hatching success, were negatively influenced by acidification. The exposure to ΔpH=−0.7 had a higher impact on the fertilization and larval viability than ΔpH=−0.4. The results suggest that the reproductive success and the biological mechanisms for calcification may be prematurely interrupted and disturbed when C. gigas veliger larvae are exposed to an acidified environment which may reduce their viability and compromise settlement and future abundances of this species.
- Ervilia castanea (Mollusca, Bivalvia) populations adversely affected at CO2 seeps in the North AtlanticPublication . Martins, Marta; Carreiro-Silva, Marina; Martins, Gustavo M.; Barcelos e Ramos, Joana; Viveiros, Fátima; Couto, Ruben P.; Parra, Hugo; Monteiro, João; Gallo, Francesca; Silva, Catarina; Teodosio, MA; Guilini, Katja; Hall-Spencer, Jason M.; Leitão, Francisco; Chicharo, Luis; Range, PedroSites with naturally high CO2 conditions provide unique opportunities to forecast the vulnerability of coastal ecosystems to ocean acidification, by studying the biological responses and potential adaptations to this increased environmental variability. In this study, we investigated the bivalve Ervilia castanea in coastal sandy sediments at reference sites and at volcanic CO2 seeps off the Azores, where the pH of bottom waters ranged from average oceanic levels of 8.2, along gradients, down to 6.81, in carbonated seawater at the seeps. The bivalve population structure changed markedly at the seeps. Large individuals became less abundant as seawater CO2 levels rose and were completely absent from the most acidified sites. In contrast, small bivalves were most abundant at the CO2 seeps. We propose that larvae can settle and initially live in high abundances under elevated CO2 levels, but that high rates of post-settlement dispersal and/or mortality occur. Ervilia castanea were susceptible to elevated CO2 levels and these effects were consistently associated to lower food supplies. This raises concerns about the effects of ocean acidification on the brood stock of this species and other bivalve molluscs of similar life history traits.
- Fish communities and environmental variables during dry season in Pampanga estuary (Philippines)Publication . Abroguena, Jeff Bogart R.; Range, Pedro; Cruz, Wilfredo; Tentia-Lagumen, Mary Chris; Chicharo, LuisBaseline assessment of fish communities and selected environmental variables (salinity, water temperature, water transparency, current speed, total suspended solid, chlorophyll a) was conducted in Pampanga estuary (Philippines) during a specific dry season (April 2010). The aims were: (a) to examine the variations of fish diversity and community structure, in relation to neap and spring tides and estuary zones and; (b) to examine the influence of environmental variables on fish communities. Reconnaissance showed that salinity was measurable at 6.8 kilometers from the rivermouth, for the surface and mid-water layers, and at 15.9 kilometers for the bottom layers, indicating the occurrence of a salt wedge. Bottom salinity was used to establish the sampling stations, grouped into 3 zones (lower 1-3, middle 4-6, upper 7-9). Sampling of fish, using otter trawl, and measurement of environmental variables were done under four tidal conditions at each station (neap low and high tide; spring low and high tide). Neap tide showed low and homogenous horizontal salinity, higher temperature, slower current speed, high TSS and chlorophyll a, whereas, spring tide showed higher salinity, horizontal saline stratification, lower temperature, faster current speed, low TSS and chlorophyll a. A total of 330 fish were captured from 32 trawl samples, encompassing 20 families and 27 species. Number of species generally did not vary between neap (20) and spring tide (18), but showed a decreasing pattern from lower to the upper estuary. Only 36% of total species were shared between neap and spring tides. Fish abundance was significantly affected by neap and spring tide, and zonation, whereas fish biomass was solely affected by zonation. Arius manillensis was the most typifying species, suggesting high probability of encounter. Chlorophyll a, TSS, salinity and current speed have a significant influence on the variations of abundance, biomass and frequency of occurrence of particular fish species. (C) 2020 Elsevier B.V. All rights reserved.
- Habitat-specific benthic metabolism in a Mediterranean-type intermittent streamPublication . Sroczynska, Katarzyna; Claro, Marilia; Range, Pedro; Wasiak, Katarzyna; Wojtal-Frankiewicz, Adrianna; Ben-Hamadou, Radhouan; Leitão, Francisco; Chícharo, LuísA modified flow-through chamber method was used to measure gross primary production (GPP), net primary production (NPP), community respiration (CR) and associated environmental variables in an intermittent Mediterranean-type stream in Southern Portugal. Three common types of in stream habitats were targeted: cobble (C), cobble covered with filamentous algae (C+A) and leaf litter (LL). NPP, GPP and CR differed significantly among all three habitats. GPP increased with chlorophyll a and, less strongly, with photosynthetic active radiation and, therefore, was highest in C+A habitat. The highest CR was in LL and its variation was best determined by ash-free dry mass (AFDM) of plant litter. Higher respiration in LL was related to heterotrophic activity and, to a lesser extent, to autotrophic respiration associated with periphyton. We observed a decrease of production efficiency of primary producers with AFDM in C+A and C habitats. Our results demonstrate that each habitat type should be considered as a discrete metabolic entity and that particular sets of environmental factors are responsible for habitat specific metabolic responses. Scaling up measurements from discrete habitat patches to the entire reach or stream should not be done by extrapolating the results of a single habitat type and will require quantification of habitat coverage, at the appropriate scale.
- Impacts of CO2-induced seawater acidification on coastal Mediterranean bivalves and interactions with other climatic stressorsPublication . Range, Pedro; Chicharo, Maria Alexandra Teodosio; Ben-Hamadou, Radhouan; Piló, David; Fernandez-Reiriz, M. J.; Labarta, U.; Marin, María Gabriella; Bressan, M.; Matozzo, V.; Chinellato, A.; Munari, M.; El Menif, N. T.; Dellali, M.; Chícharo, LuísThe effects of seawater acidification caused by increasing concentrations of atmospheric carbon dioxide (CO2), combined with other climatic stressors, were studied on 3 coastal Mediterranean bivalve species: the mussel Mytilus galloprovincialis and the clams Chamelea gallina and Ruditapes decussatus. CO2 perturbation experiments produced contrasting responses on growth and calcification of juvenile shells, according to species and location. In the Northern Adriatic (Italy), long-term exposure to reduced pH severely damaged the shells of M. galloprovincialis and C. gallina and reduced growth for the latter species. Seawater in the Ria Formosa lagoon (Portugal) was consistently saturated in carbonates, which buffered the impacts on calcification and growth. After 80 days, no shell damage was observed in Portugal, but mussels in the acidified treatments were less calcified. Reduced clearance, ingestion and respiration rates and increased ammonia excretion were observed for R. decussatus under reduced pH. Clearance rates of juvenile mussels were significantly reduced by acidification in Italy, but not in Portugal. Both locations showed a consistent trend for increased ammonia excretion with decreasing pH, uggesting increased protein catabolism. Respiratory rates were generally not affected. Short-term factorial experiments done in Italy revealed that acidification caused alterations in immunological parameters of adult bivalves, particularly at temperature and salinity values far from the optimal for the species in the Mediterranean. Overall, our results showed large variations in the sensitivities of bivalves to climatic changes, among different species and between local populations of the same species. Expectations of impacts, mitigation and adaptation strategies have to consider such local variability.
- «
- 1 (current)
- 2
- 3
- »