Papers by Bernardo Duarte
In highly industrialized estuaries, there is also a large input of heavy metals, which are accumu... more In highly industrialized estuaries, there is also a large input of heavy metals, which are accumulated in salt marsh sediments. These high inputs make salt marshes key zones for the biogeochemis-try of the estuary, but also for metal cycling. When accumulated in salt marsh sediments, metals can become adsorbed to the sediment constituents and taken up by plant roots and translocated to above-ground plant organs. This plant metal uptake is a very important factor in estuarine reme-diation. Halimione portulacoides and Spartina maritima are two of the more abundant species in the Mediterranean salt marshes. Plants are known to exudate by their roots low-molecular-weight organic acids (LMWOA) to scavenge metallic elements important for their metabolism and/or in other cases to maintain these metallic elements outside their tissues to avoid toxicity cases. This work explores LMWOA's natural interaction with metallic ions and how they can influence the phy-toremediation potential of t...
Salt marshes are a very important part of the estuarine ecosystem, with an important role within ... more Salt marshes are a very important part of the estuarine ecosystem, with an important role within the biogeochemical cycles, being areas of high primary production, which also contribute importantly as shoreline stabilizers. Besides, periodical tidal flooding of salt marshes also causes the transport of significant quantities of pollutants, which tend to accumulate in the marsh ecosystem. Therefore, salt marshes are considered to be important sinks namely of heavy metals. Their important role has been recently admitted by the inclusion of these ecosystems in the European Water Framework Directive (WFD). Multiple services of wetlands and its value are already well known. The Tagus estuary is the largest estuary in Western Europe, covering an area of approximately 320 km 2 . The estuary has a vast inner bay with extensive intertidal areas from which about 15% of these areas are salt marshes. The Tagus estuary is a mesotidal system with a mean tidal range of 2.4 m, varying from about 1
Salt marshes provide environmental conditions that are known to affect metal speciation in sedime... more Salt marshes provide environmental conditions that are known to affect metal speciation in sediments. The elevational gradient along the marsh and consequent differential flooding are some of the major factors influencing halophytic species distribution and coverage due to their differential tolerance to salinity and submersion. Different species, in turn, also have distinct influences on the sediment's metal speciation, and its metal accumulation abilities. The present work aimed to evaluate how different halophyte species in two different salt marshes could influence metal partitioning in the sediment at root depth and how that could differ from bare sediments. Metal speciation in sediments around the roots (rhizosediments) of Halimione portulacoides, Sarcocornia fruticosa and Spartina maritima was determined by sequentially extracting operationally defined fractions with solutions of increasing strength and acidity. Ros ario salt marsh generally showed higher concentrations of all metals in the rhizosediments. Metal partitioning was primarily related to the type of metal, with the elements' chemistry overriding the environment's influence on fractionation schemes. The most mobile elements were Cd and Zn, with greater availability being found in non-vegetated sediments. Immobilization in rhizosediments was predominantly influenced by the presence of Fe and Mn oxides, as well as organic complexes. In the more mature of both salt marshes, the differences between vegetated and non-vegetated sediments were more evident regarding S. fruticosa, while in the younger system all halophytes presented significantly different metal partitioning when compared to that of mudflats.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights a b s t r a c t Different characteristics of Spartina maritima found in two distinct salt marshes located in different estuaries were analysed through interpretation of their local hydrodynamic patterns, as well as the impact of sea level rise on physical processes and consequently on plant dynamics and salt marshes stability. These salt marshes are situated in two of the most important Portuguese coastal systems, Tagus estuary (Rosário salt marsh) and Ria de Aveiro lagoon (Barra salt marsh), which are dominated by physical processes that induce strong tidal currents. They were monitored during one year and plant and sediment samples of S. maritima were collected quarterly in order to determine the vegetation coverage, above and belowground biomass, organic matter and sediment moisture. Residual circulation, tidal asymmetry and tidal dissipation were determined from numerical modelling results of the MOHID 2D model that was applied to each coastal system, considering the actual sea level and a sea level rise (SLR) scenario. Results suggest that the different characteristics found for Spartina maritima in the Rosário and the Barra salt marshes may be related with the diverse hydrodynamic conditions identified for each salt marsh. Consequently, the exploration of SLR scenario predictions indicates how these salt marshes could evolve in the future, showing that the important changes in these hydrodynamic parameters under climate change context might induce significant modifications in the salt marshes dynamics and stability. SLR scenario could lead to changes in nutrients and sediments patterns around the salt marshes and thus vegetation coverage percentage would be affected. Additionally, as a consequence of flood duration increase , sediment moisture will increase causing a stress condition to plants. Hence, the ratio below/ aboveground biomass might increase, becoming critical to plants survival under conditions of accelerated sea level rise. Accordingly, both SLR and expected changes in vegetation coverage percentage in controlling salt marshes evolution have important implications in their stability and consequently in coastal management. These conditions are unlikely to be unique to these salt marshes and it is suggested that similar analyses are replicated for other tidally dominated systems to improve understanding and characterization of their dynamics and stability under climate change context.
Juncus acutus arises as possible hyperaccumulator specie, tolerating exogenous Zn concentrations ... more Juncus acutus arises as possible hyperaccumulator specie, tolerating exogenous Zn concentrations as high as 60 mM. Zinc concentrations here detected in seedlings germinated in the presence high Zn concentrations , were above the described upper toxic levels for higher plants. Even at the highest Zn concentration, growth inhibition only accounted to approximately 30% of control seedlings biomass, presenting an EC 50 value in the range of 10–20 mM of metal. PSII quantum yields showed a marked decline, reflection of changes in the thylakoid structure on the PSII electron donor sites. In fact, the electron transport rate was severely affected by Zn in seedlings exposed to higher Zn concentrations leading to a decrease in their maximum electronic transport rate and consequently presenting lower light saturation and lower photosynthetic efficiencies. Although light absorption capacity was not affected by Zn exposure and uptake, energy trapping flux in the photosynthetic apparatus and transport throughout the electronic chain was severely impaired. This lack of efficiency is related with non-functional Zn-chlorophylls formation. There was a strong linear correlation between exogenous Zn concentration applied and the concentration actually verified in the seedlings tissue with the concentration of both ZnChl a and b. There was also a gradual loss of connectivity between the antennae of the PSII units being this more evident at the higher Zn concentrations and thus impairing the energetic transport. The reduction in light harvesting efficiency, leads inevitably to the accumulation of redox energy inside the cells. To counteract ROS generation, all anti-oxidant enzymatic activities (except catalase) showed a proportional response to exogenous and in vivo Zn concentrations. Not only this plant appears to be highly tolerant to high Zn concentrations , but also it can overcome efficiently the damage produced during this uptake by efficiently dissipating the excessive cellular redox potential accumulated, essentially due to Zn incorporation into the chlorophyll molecule.
Nowadays, there is a special concern about the possible impact of sea level rise in hydrodynamic ... more Nowadays, there is a special concern about the possible impact of sea level rise in hydrodynamic patterns of coastal systems and its consequence in contingent ecosystems. In the present work, the effects of sea level rise in residual circulation are analyzed in two of the most important Portuguese coastal systems, Ria de Aveiro lagoon and Tagus estuary. The role of rivers inflow on residual circulation is also analyzed under different sea level scenarios. Several projections of river discharges were considered and two scenarios for sea level were adopted: actual and locally predicted sea level rise. The methodology followed comprises the exploitation of previously validated 2D hydrodynamic numerical models (MOHID) developed for both systems. Results indicate that rivers discharge effect cannot be unconsidered in the long term hydrodynamic analysis for both systems, once residual currents intensity could be at least 40% and even 100% higher in maximum inflow than in typical inflow and no discharges scenarios, respectively. In Tagus estuary, the upper bay is the most affected area in a sea level rise scenario, namely in the upper zone (with extensive intertidal areas) where differences in the residual currents intensity can be higher than 100%. In Ria de Aveiro lagoon, differences between actual and sea level rise could be higher than 80%. Narrow and shallow channels are the most affected areas, revealing the significant impact of sea level rise in the intertidal zones. Consequently, the predicted changes in these systems hydrodynamics could influence the long term transport and their actual equilibrium and, as such, affect the natural state of the contingent biological communities.
Trace metal elements can cause various environmental and health issues due to their accumulation ... more Trace metal elements can cause various environmental and health issues due to their accumulation and integration in the food chain. In the present study, we determined the major toxic effects of arsenic on physiological behaviour of plants. For this propose, several combinations of high salinity and arsenic (As) concentrations were applied to the halophytic shrub, Tamarix gallica, by growing for three months with an irrigation solution supplemented with different concentrations of As (0, 200, 500 and 800 M) with and without 200 mM NaCl. The effect of the combined stress conditions on growth, physiological patterns and biochemical parameters were also assessed. The results demonstrated that T. gallica is a tolerant plant regarding arsenic. The photosynthesis apparatus Fo, Fm and Fv fluorescence, as well as Fv/Fm were not affected by As nor by As combined with salt. Likewise, pigment and nutrient (K + , Ca 2+ and Mg 2+) contents were not affected either. However, the study results revealed that As adversely and significantly influenced the growth with increasing the concentration of As. Despite shoots growth reduction, the present research demonstrates that T. gallica is able to cope with high external concentrations of As (under 500 lM) alone or in combination with NaCl.
Estuaries and coastal lagoons around the world are wetlands of great importance and they are regu... more Estuaries and coastal lagoons around the world are wetlands of great importance and they are regularly targeted as prime conservation sites. Many include wildlife refuges and have nature reserves that were set up in areas preserved from development in order to keep valuable species and habitats, while maintaining traditions and sustained use. Tidal wetlands are often mentioned in the literature as natural habitats with high biological productivity. The net primary production in a salt marsh is often higher than in temperate or tropical forests and this productivity is directly linked to the important role halophytes play in estuaries, in terms of the value-added. Salt marshes may be a sink of heavy metals. The ability to phytostabi-lize contaminants in the rhizo-sediment is an important aspect in the self-remediative processes and biogeochemistry of this ecosystem, and will help fi ltering natural and anthropogenic loads of nutrients and pollutants discharged into the wetland. There is also a provision of rare and unique habitats, which support nursery grounds for commercial fi sh and wildlife, including vital feeding grounds for many migratory birds. Rediscovered as a new source of amenity and leisure activities for the population living in urban areas, salt marsh halophytes and estuaries have an important role in the preservation of biodiversity. In this paper we discuss the support of the salt marsh ecosystem to the estuarine birds, and consequently its contribution for biodiversity. The wealth of life in estuarine systems has been known to our early ancestors and wetlands of this type were source of food and amenities to groups of hunter-gatherers, many thousand years before the foundation of cities and permanent human settlements.
Several works have evidenced in the past the importance and influence of plants and terrestrial i... more Several works have evidenced in the past the importance and influence of plants and terrestrial invertebrates in metal availability in soils and sediments through changes in metal speciation. In contrast, the impact of estuarine invertebrates and fishes in this process has been poorly explored. The partition of metals in estuarine surface sediments was studied in a controlled environment according to four operationally defined fractions. Sediments were analyzed before and after the passage through the gut of two detritivorous species. Scrobicularia plana feeds on the bottom and suspended sediment particles through the inhalant siphon. Liza ramada is an interface feeder, filtering the superficial layer of the sediment and suspended particles in the water column. Cd, Cu and Ni bound to carbonates increased in the pellets of S. plana, compared with the ingested sediment, as did exchangeable Zn. Similarly, Cd and Zn bound to carbonates have also increased in the pellets of L. ramada; on the contrary, a decrease of Ni was observable in the pellets of this fish. The outcome of the controlled experiments pointed to a potential increase in some metals' availability in the estuarine environment, as a result of the more mobile metal forms in the excreted fecal pellets. This draws the attention to a relevant impact of the trophic activity of both species, alongside with the potential enhancement brought to it by the bioturbation promoted by them, in the role that the estuary itself has as a contaminants' buffer.
A B S T R A C T Early diagenetic processes and anthropogenic activities are responsible for metal... more A B S T R A C T Early diagenetic processes and anthropogenic activities are responsible for metal enrichment in estuarine sediments. The Tagus estuary (Portugal) is no exception, and as a result of past and present pressures, surface sediment contamination is still an issue in some areas. Since such metal loads may be incorporated by benthic organisms, this study analyzed the accumulation of trace metals in the Lusitanian toadfish (Halobatrachus didactylus) in the Tagus estuary. In order to determine the role played by the seasonal reproductive cycle of the Lusitanian toadfish in the bioaccumulation process of trace metals in its tissues, the concentrations of Cd, Co, Cr, Cu, Ni, Pb and Zn were determined in the liver of male and female specimens captured during reproductive and non-reproductive periods. The results showed that metal accumulation in the liver was related simultaneously with gender and season, with females having higher levels of Cd, Cu and Zn during the reproductive period. The metabolic roles of Cu and Zn in embryonic development may explain such results, as both metals accumulated in the female liver to be transported to the gonads later on. Cd, on the other hand, does not have a metabolic role, and the higher concentrations of this metal found in spawning females could be related to the high affinity of Cd to vitellogenin, which is produced in the liver. To assess the species' potential as an indicator of metal contamination, the concentrations of the seven elements were compared in the muscle tissue of adult, type I males (age !5), from two areas with distinct sediment metal loads. Non-essential metals in the muscle reflected the same differences between areas that were found in the sediment samples, evidencing H. didactylus as a potential indicator of those elements bioavailability from the sediment. The results showed that the muscle tissue of adult specimens of a relatively sedentary species such as H. didactylus is a useful indicator of long term accumulation of trace metals. On the contrary, liver concentrations of trace metals showed variation according to the reproductive status, which could lead to overestimate of the environmental status concerning trace metals bioavailability. Spawning season and liver tissue should thus be avoided in biomonitoring studies targeting this benthic fish.
The increasing metal pollution in salt marshes and its influence on the plants that inhabit these... more The increasing metal pollution in salt marshes and its influence on the plants that inhabit these ecosystems , has become a major concern with serious implications on the species establishment. Juncus acutus is a highly common halophyte specie in Portuguese marshes. Seeds from his specie were exposed to a range of different Cd concentrations (0.05, 0.1, 0.5 and 1 mM) in order to evaluate the effects of acute Cd stress on seed germination and growth as well as on seedling pigment composition, photosynthetic apparatus and oxidative stress biomarkers. Seedling length was higher than in control in every Cd treatment, however biomass showed a decrease. It was also observed that increasing Cd treatments, lead to a proportional increase in the Cd tissue concentration. Also the Cd-substituted chlorophylls showed an increase with increasing Cd doses that were applied. This substitution results in a non-functional chlorophyll molecule, highly unstable under moderate light intensities which inevitably reduces the efficiency of the LHC II. As consequence, there was a decrease in the use-efficiency of the harvested energy, leading to a decay in the photosynthetic capacity and energy accumulation, which was dissipated as heat. As for the antioxidant enzymes, SOD and APX presented higher activity, responding to increasing cadmium concentrations. Thus, becomes evident that Cd affects negatively, both biochemically and photochemically, the establishment by seed process of J. acutus highlighting the potential of the use of this specie seed as potential sentinel and ecotoxicity test in extreme conditions.
Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinf... more Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world's oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits.
Physicochemical (organic matter content, relative humidity, humic acid content, carbon, nitrogen ... more Physicochemical (organic matter content, relative humidity, humic acid content, carbon, nitrogen and phosphorous content) and microbiological activities (extracellular enzymatic activities, basal and sub-strate induced respiration and bioenergetical parameters) were evaluated in salt marsh degraded sediments, during a 1 year revegetation trial starting at the end of the growing season. For this reveg-etated with Halimione portulacoides and also in nearby sediments with savage H. portulacoides plants and bare sediments were monitored for comparison proposes. Sediments colonized by savage plants showed higher water content, organic matter, carbon, nitrogen and phosphorous contents, in contrast with the low values observed in bare and colonized by transplants sediments. Overlooking the microbial metabolic and respiratory parameters it was observed that the more efficient microbial communities were present in the sediments colonized by the savage plants. Also the extracellular enzymes showed differences. In the transplant colonized sediments and also in the bare ones, peroxidase showed high and similar activities. By the contrary urease showed lower in these last sediments. Only acid phosphatase showed a different trend being higher in the bare sediments and in the sediments colonized by savage plants. Applying a rhizosphere sediment microbial index (RSMI) it was assessed that the more important factors for these sediments evaluation were the Basal respiration, urease activity, metabolic coefficient, total phosphorous content and total carbon content. Using this index for evaluation it showed not only that the sediments colonized by savage plants presented microbial quality, but also it was shown that the bare sediments and the sediments colonized by the transplants after a 1 year period still have the same microbial characteristics and thereby similar microbial qualities. This allowed to conclude that over the duration of this experiment, the revegetated sediments were still far from reaching the quality levels of the sediments naturally colonized, indicating that the 1 year period of revegetation was not enough to a successful restoration of a degraded salt marsh. Although the restoration process was not successful, the elaboration of the RSMI proved to be useful with applications in future monitorization programs.
Worldwide estuarine ecosystems are by their privileged geographic location, anthropogenically imp... more Worldwide estuarine ecosystems are by their privileged geographic location, anthropogenically impacted systems. Heavy metal contamination in estuarine waters and sediments are well known to be one of the most important outcomes driven from human activities. The partitioning of these elements has been widely focused, due to its importance not only on the estuarine biogeochemistry but also on its bioavailability to the trophic webs. As observed in other estuaries, in the Tagus basin, no increase in the partition coefficients with the increasing suspended particulate matter concentrations was observed, mostly due to a permanent dilution process of the suspended matter, rich in heavy metals and less contaminated and resuspended bottom sediments. Another important outcome of this study was the common origin of all the analysed heavy metals, probably due to the large industrialization process that the margins of the Tagus estuary suffered in the past, although no relationship was found with the presence of the different discharge areas. In fact, metal partitioning seems to be mostly influenced by the chemical species in which the pollutant is delivered to the system and on water chemistry, with a higher emphasis on the metal cycling essentially between the particulate and dissolved phase. This partitioning system acquires a relevant importance while evaluating the impacts of marine construction and the associated dredging operations, and consequent changes in the estuarine water chemistry.
Soil salinization is one of the most important factors impacting plant productivity. About 3.6 bi... more Soil salinization is one of the most important factors impacting plant productivity. About 3.6 billion of the world's 5.2 billion ha of agricultural dry land, have already suffered erosion, degradation, and salinization. Halophytes are typically considered as plants able to complete their life cycle in environments where the salt concentration is above 200 mM NaCl. Salinity adjustment is a complex phenomenon but essential mechanism to overcome salt stress, with both biophysical and biochemical implications. At this level, halophytes evolved in several directions, adopting different strategies. Otherwise, the lack of adaptation to a salt environment would negatively affect their electron transduction pathways and the entire energetic metabolism, the foundation of every plant photosynthesis and biomass production.The maintenance of ionic homeostasis is in the basis of all cellular counteractive measures, in particular in terms of redox potential and energy transduction. In the present work the biophysical mechanisms underlying energy capture and transduction in halophytes are discussed alongside with their relation with biochemical counteractive mechanisms, integrating data from photosynthetic light harvesting complexes, electron transport chains to the quinone pools, carbon fixation, and energy dissipation metabolism.
The recent IPCC WG2 5th Assessment
Salt marsh environments are harsh environments where salinity comprises one of the most important... more Salt marsh environments are harsh environments where salinity comprises one of the most important species distribution shaping factor, presenting sediment salinities from 0 to 855 mM (0e50 ppt). Invasive species have often a high colonizing potential, due to its high plasticity and adaptation ability. Spartina patens is an invasive species already spread along several Mediterranean countries, like France and Spain. Cyperus longus is typically a freshwater species that has been spreading across the Mediterranean. In order to evaluate the ecophysiological fitness of these species, mesocosmos trials were performed subjecting both species to increasing realistic salinity levels and their photochemical and biochemical feedback was evaluated. Both species presented very different behaviours. S. patens appears to be insensitive to salt stress, mostly due to elevated proline concentrations in its leaves allowing it to maintain its osmotic balance, and thus preventing the damaging of its photochemical mechanisms. C. longus, on the other hand, was highly affected by elevated salt levels mostly due to the lack of osmotic balance driven by an incapacity to counteract the elevated ionic strength of the external medium by osmocompatible solutes. S. patens is physiologically highly adapted to saline environments and thus is capable to colonize all the marsh saline environments, while C. longus appears to be an opportunistic invader colonizing the marsh during periods of lower salinities typical from rainy seasons.
Salt marshes are very important areas for biogeochemical cycling, sediment accretion, pollution f... more Salt marshes are very important areas for biogeochemical cycling, sediment accretion, pollution filtration and retention and erosion and stabilization of the river margins. The high organic matter content in the salt marsh plant sediments along with the radial oxygen diffusion provided by these halophyte root systems gather the ideal conditions for the development of a microbial rhizosphere community. Due to the quick feedback of the microbial communities to an environmental change, these organisms become important monitors for environmental impact assessment. A Salt marsh Sediment Microbial Index (SSMI) that reflected physical–chemical and microbial parameters was applied to plant rhizosphere sediments of five salt marshes from three important water bodies from Portugal. The SSMI revealed to be plant-independent evaluating efficiently the different marshes according to their maturity degree and disturbance influence. Mature salt marshes SSMI classification grouped all the systems at this development stage, while the younger salt marshes are classified in different groups according to their evolution degree. Also the impact degree is reflected at this level discriminating also the more adversely impacted salt marshes. Being a multi-metric index, the SSMI sub-metrics are also susceptible of ecological interpretation , giving important backstage information about the underlying biogeochemical cycling processes.
Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication ... more Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication problems, phosphorous represents another key element, and consequently its biogeochemical cycling has a crucial role in eutrophication processes. Microbial communities are a central component in trophic dynamics and biogeochem-ical processes on coastal systems, since most of the processes in sediments are microbial-mediated due to enzymatic action, including the mineralization of organic phosphorus carried out by acid phosphatase activity. In the present work, the authors investigate the biogeochemical sediment drivers that control phosphatase activities. Authors also aim to assess biogeochemical factors' influence on the enzyme-mediated phosphorous cycling processes in salt marshes. Plant rhizosediments and bare sediments were collected and biogeochemical features, including phosphatase activities, inorganic and organic phosphorus contents, humic acids content and pH, were assessed. Acid phosphatase was found to give the highest contribution for total phosphatase activity among the three pH-isoforms present in salt marsh sediments, favored by acid pH in colonized sediments. Humic acids also appear to have an important role inhibiting phosphatase activity. A clear relation of phosphatase activity and inorganic phosphorous was also found. The data presented reinforces the role of phosphatase in phosphorous cycling.
Uploads
Papers by Bernardo Duarte