Loading...
11 results
Search Results
Now showing 1 - 10 of 11
- Seawater acidification by CO2 in a coastal lagoon environment: Effects on life history traits of juvenile mussels Mytilus galloprovincialisPublication . Range, Pedro; Piló, David; Ben-Hamadou, Radhouan; Chicharo, Maria Alexandra Teodosio; Matias, Domitília; Joaquim, Sandra; Oliveira, A. P.; Chícharo, LuísThe carbonate chemistry of seawater from the Ria Formosa lagoon was experimentally manipulated, by diffusing pure CO2, to attain two reduced pH levels, by−0.3 and−0.6 pH units, relative to unmanipulated seawater. After 84 days of exposure, no differences were detected in terms of growth (somatic or shell) or mortality of juvenile mussels Mytilus galloprovincialis. The naturally elevated total alkalinity of the seawater (≈3550 μmol kg−1)prevented under-saturation of CaCO3, evenunder pCO2 values exceeding 4000 μatm, attenuating the detrimental effects on the carbonate supply-side. Even so, variations in shell weight showed that net calcification was reduced under elevated CO2 and reduced pH, although the magnitude and significance of this effect varied among size-classes. Most of the loss of shell material probably occurred as post-deposition dissolution in the internal aragonitic nacre layer. Our results show that, even when reared under extreme levels of CO2-induced acidification, juvenileM. galloprovincialis can continue to calcify and grow in this coastal lagoon environment. The complex responses of bivalves to ocean acidification suggest a large degree of interspecific and intraspecific variability in their sensitivity to this type of perturbation. Further research is needed to assess the generality of these patterns and to disentangle the relative contributions of acclimation to local variations in seawater chemistry and genetic adaptation.
- Use of a hydrotechnical infrastructure (Alqueva dam) to regulate planktonic assemblages in the Guadiana estuary: basis for sustainable water and ecosystem services managementPublication . Chícharo, Luís; Teodosio, Maria; Ben-Hamadou, RadhouanThe phytoplankton and zooplankton assemblages in the Guadiana estuary (south Portugal) were compared in two contrasting hydrologic years, characterized by high and low freshwater discharges. Changes in salinity, nutrients and turbidity, which were mainly due to the changes in freshwater input, had an important influence on the structure of the planktonic assemblages. Nevertheless, coastal upwelling can also influence the productivity of the lower estuarine area during short periods both in winter and in summer. In 2000, a short-term freshwater pulse during May (average 126.46 m3 s 1) was markedly beneficial; phytoplanktonic diversity increased, and this caused an increase in zooplanktonic diversity. As phyto-zooplankton coupling in these systems is an important regulator of processes in the trophic web, changes in the dominant groups can have consequences on water quality, especially on the occurrence of toxic plankton blooms. Modelling simulations indicate that a day discharge of 50 m3 s 1, every week during critical periods, such as summer/autumn, could be enough to avoid cyanobacteria blooms. Since freshwater ‘‘pulses’’ can be managed by operating the freshwater release from hydrotechnical structures, understanding the relationships between the periodicity and magnitude of inflow pulse events and the estuarine ecosystem structure and healthy functioning is a crucial step towards the development of management modelling tools, as proposed in this study.
- Selection of coastal estuarine habitats by atherina boyeri larvae in laboratory experimentsPublication . Gonçalves, Renata Isabel de Sousa; Ben-Hamadou, Radhouan; Chícharo, LuísCoastal wetlands are important nursery areas for many fish species as they provide food, refuge from predators and optimal hydrodynamic conditions. The impact of anthropogenic and environmental changes on ecological functions of these areas need to be identified as a basis for establishing adequate ecohydrological measures for the long-term sustainability of the ecosystem and its associated services. Patterns of habitat selection were examined in wild-caught larvae of Atherina boyeri (Risso, 1810), by means of microcosms experiments. We simulated three habitats representative of vertical marsh profile at Guadiana wetland, non-vegetated bottom (sand) and two vegetation types (Spartina maritima and Sarcorcornia spp.), in experimental units and monitored fish larvae spatial distribution by video-recording. We observed a strong avoidance of both vegetated habitats suggesting that habitat choice behavior may be dependent on external stimuli such as current velocity, predator effect and food availability. Similar experiments including external factors are required to unravel the behavioral responses of A. boyeri to different types of habitat.
- 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.
- Relative sensitivity of soft-bottom intertidal macrofauna to increased CO2 and experimental stressPublication . Range, Pedro; Martins, M.; Cabral, Sara; Piló, David; Ben-Hamadou, Radhouan; Chicharo, Maria Alexandra Teodosio; Miguel de Sousa Leitão, Francisco; Drago, T.; Oliveira, A. P.; Matias, D.; Chícharo, LuísWe used a controlled CO2 perturbation experiment to test hypotheses about changes in diversity, composition and structure of soft-bottom intertidal macrobenthic assemblages, under realistic and locally relevant scenarios of seawater acidification. Patches of undisturbed sediment were collected from 2 types of intertidal sedimentary habitat in the Ria Formosa coastal lagoon (South Portugal) and exposed to 2 levels of seawater acidification (pH reduced by 0.3 and 0.6 units) and 1 unmanipulated (control) level. After 75 d the assemblages differed significantly between the 2 types of sediment and between field controls and the ex situ treatments, but not among the 3 pH levels tested. The naturally high values of total alkalinity buffered seawater from the changes imposed on carbonate chemistry and may have contributed to offsetting acidification at the local scale. Observed differences on biota were strongly related to the organic matter content and grain-size of the sediments, particularly to the fractions of medium and coarse sand. Soft-bottom intertidal macrofauna was significantly affected by the stress of being held in an artificial environment, but not by CO2-induced seawater acidification. Given the previously observed variations in the sensitivities of marine organisms to seawater acidification, direct extrapolations of the present findings to different regions or other types of assemblages do not seem advisable. However, the contribution of ex situ studies to the assessment of ecosystem-level responses to environmental disturbances could generally be improved by incorporating adequate field controls in the experimental design.
- The effect of distinct hydrologic conditions on the zooplankton community in an estuary under mediterranean climate influencePublication . Petra Muha, Teja; Chícharo, Luís; Morais, P.; Pereira, Rita; Ben-Hamadou, Radhouan; Cruz, Joana; Teodosio, MariaSeveral studies have documented effects of hydrological conditions influencing fish and benthonic communities in estuaries and coastal areas, but only few evidences of freshwater discharge on zooplankton assemblages are found. The major finding of our study in an estuary under climate variability with regulated flow by dams is that increased annual flow leads to an increase in abundance and diversity of zooplankton and decrease of jellyfish blooms. This offers suitable nursery conditions with positive consequences on the food-web functioning. The ecohydrological approach of dual regulation could be useful with controlling the timing, frequency and volume of freshwater inflow by altering dams' operational efficiency, leading to healthy functional environment and optimize adaptability to climatic changes.
- 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.
- 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.
- 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.
- 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.