Influence of bioturbation by Hediste diversicolor on mercury fluxes from estuarine sediments: a mesocosms laboratory experiment     

Cardoso PG  Lillebø AI  Lopes CB  Pereira E  Duarte AC  Pardal MA 《Marine pollution bulletin》2008,56(2):325-334

Mercury, with its reactive forms being the most deleterious for the trophic chains, has been identified as a major pollutant in a few confined bodies of the coastal zone. Due to feeding, burrowing, and bioirrigation activities, infauna are known to play a crucial role in the biogeochemical processes of contaminants. The main goal of the present study is to evaluate the effects of Hediste diversicolor bioturbation on mercury fluxes from estuarine sediments in a mesocosms laboratory experiment. Additionally, an attempt was made to establish a relationship between the amount of remobilised mercury to the water column and the degree of contamination of the sediments using a mercury contamination gradient. The present experiment demonstrated that the bioturbation activity caused by the gallery-diffuser H. diversicolor did not influence the remobilisation of mercury (in dissolved reactive forms) from the sediment to the water column. The concentration of dissolved reactive mercury in the water column also did not reflect the degree of contamination in the sediments. The results obtained were in accordance with the sediment characteristics of the Mondego Estuary and Ria de Aveiro (Portugal), since they are very rich in organic matter content, iron/manganese total and hydrous oxides. These physicochemical characteristics of the sediments may partially justify the retention of mercury by these systems, even when they are subjected to bioturbation. In conclusion, sediments with high organic matter content and a high concentration of iron/manganese hydrous oxides allowed for efficient retention of mercury, and the bioturbation process did not seem to affect the system. Another conclusion from this study is that the remobilisation of mercury by bioturbation to the water column is not a fast process, requiring more than 24h. This study constitutes an important work in the area of the effects of bioturbation on mercury remobilisation. Considering the toxicity of mercury for the biota, it is essential to evaluate the real magnitude of mercury processes occurring in estuarine systems in order to obtain essential information on metal behaviour.  相似文献   

The impact of extreme weather events on the seagrass Zostera noltii and related Hydrobia ulvae population     

Cardoso PG  Raffaelli D  Pardal MA 《Marine pollution bulletin》2008,56(3):483-492

Coastal areas are typically subjected to a range of stressors, but they now face the additional stressor of climate change, manifested in part by an increased intensity and frequency of extreme weather events. Thus, the Mondego estuary (Portugal) has experienced organic enrichment (eutrophication) issues and these are potentially exacerbated by extreme weather events (floods, droughts and heat waves). In this paper, we explore the impact of interactions of these different stressors on the ecology of the system, specifically on the two key components, the seagrass Zostera noltii and the mud snail Hydrobia ulvae. Extreme events affected different components of the estuarine ecosystem (primary producers and macrofauna) differently. Whilst the floods directly impacted on H. ulvae, by wiping out part of its population, they did not directly affect the biomass of Z. noltii. In contrast, drought events, through their effects on salinity, directly impacted the biomass of Zostera, which had knock-on effects on the dynamics of H. ulvae. We conclude that over the period when the estuary experienced eutrophication, extreme weather events contributed to the overall degradation of the estuary, while during the recovery phase following the introduction of a management programme, those extreme weather episodes delayed the recovery process significantly.  相似文献   

Hydro‐morphodynamic evolution in a 90° movable bed discordant confluence with low discharge ratio          下载免费PDF全文

Sebastián Guillén‐Ludeña  Mário J. Franca  António H. Cardoso  Anton J. Schleiss 《地球表面变化过程与地形》2015,40(14):1927-1938

Confluences with low discharge and momentum ratios, where narrow steep tributaries with high sediment load join a wide low‐gradient main channel that provides the main discharge, are often observed in high mountain regions such as in the upper‐Rhone river catchment in Switzerland. Few existing studies have examined the hydro‐morphodynamics of this type of river confluence while considering sediment discharge in both confluent channels. This paper presents the evolution of the bed morphology and hydrodynamics as observed in an experimental facility with a movable bed. For that purpose, one experiment was carried out in a laboratory confluence with low discharge and momentum ratios, where constant sediment rates were supplied to both flumes. During the experiment, bed topography and water surface elevations were systematically recorded. When the bed topography reached a steady state (so‐called equilibrium) and the outgoing sediment rate approximated the incoming rate, flow velocity was measured at 12 different points distributed throughout the confluence, and the grain size distribution of the bed surface was analyzed. Typical morphodynamic features of discordant confluences such as a bank‐attached bar and a flow deflection zone are identified in this study. Nevertheless, the presence of a marked scour hole in the discordant confluence and distinct flow regimes for the tributary and main channel, differ from results obtained in previous studies. Strong acceleration of the flow along the outer bank of the main channel is responsible for the scour hole. This erosion is facilitated by the sediment discharge into the confluence from the main channel which inhibits bed armoring in this region. The supercritical flow regime observed in the tributary is the hydrodynamic response to the imposed sediment rate in the tributary. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Benthic macroinvertebrates' vertical distribution in the Tagus estuary (Portugal): The influence of tidal cycle     

Inês Cardoso  José Pedro Granadeiro  Henrique Cabral 《Estuarine, Coastal and Shelf Science》2010

In this work we evaluated the vertical distribution pattern of benthic infauna during the tidal cycle at one of the most important mudflats of the Tagus estuary. Samples were collected hourly during 24 h periods at four complete tidal cycles, using a corer specifically designed for the study purpose that allowed easy and effective separation of 15 different sediment layers. A particular case of general linear models, the hurdle model, was used to analyse data sets. We found that different species have different distribution and abundance according to sediment layers. Results showed that individuals tend to go deeper into sediment with a lower water column height and that these migrations are more visible during spring tides.  相似文献   

Reconstruction of food conditions for Northeast Atlantic bivalve species based on Dynamic Energy Budgets     

Vnia Freitas  Joana F.M.F. Cardoso  Sílvia Santos  Joana Campos  Jan Drent  Sofia Saraiva  Johannes IJ. Witte  Sebastiaan A.L.M. Kooijman  Henk W. Van der Veer 《Journal of Sea Research》2009,62(2-3):75

Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions.  相似文献   

The impact of extreme flooding events and anthropogenic stressors on the macrobenthic communities’ dynamics     

P.G. Cardoso  D. Raffaelli  A.I. Lillebø  T. Verdelhos  M.A. Pardal 《Estuarine, Coastal and Shelf Science》2008

Marine and coastal environments are among the most ecologically and socio-economically important habitats on Earth. However, climate change associated with a variety of anthropogenic stressors (e.g. eutrophication) may interact to produce combined impacts on biodiversity and ecosystem functioning, which in turn will have profound implications for marine ecosystems and the economic and social systems that depend upon them.  相似文献   

Modern sedimentation processes in a wave-dominated coastal embayment: Espírito Santo Bay,southeast Brazil     

Alex Cardoso Bastos  Daphnne Moraes Costa Moscon  Dannilo Carmo  José Antonio Baptista Neto  Valéria da Silva Quaresma 《Geo-Marine Letters》2015,35(1):23-36

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Effects of extreme climate events on the macrobenthic communities' structure and functioning of a temperate estuary     

Grilo TF  Cardoso PG  Dolbeth M  Bordalo MD  Pardal MA 《Marine pollution bulletin》2011,62(2):303-311

The Mondego estuary (Portugal) experienced profound structural and functional modifications due to eutrophication, which was exacerbated by consecutive weather extremes that compromised a previous restoration project. This work explores multiple climate impacts on macrobenthic communities’ structure and functioning and its implications on ecosystem’s recovery. Floods and heat waves had a stronger negative effect on macrobenthic assemblages than the droughts, imposing a total abundance decline. Contrarily, biomass was not so affected by climate events, being stable and even increased in a mudflat area, where seagrass is re-colonizing. Bivalves and oligochaetes decreased with the flooding episodes, likewise subsurface-deposit feeders and suspension feeders, while crustaceans were particularly sensitive to heat waves. Species richness declined with the floods and heat waves, whilst evenness increased in sandflat area, constituting a positive sign towards recovery. Succession of different climate extremes affected ecosystem structure and functioning, delaying its recovery with possible consequent effects at higher trophic levels.  相似文献   

Fish assemblages of small estuaries of the Portuguese coast: A functional approach   总被引：1，自引：0，他引：1  

Inês Cardoso  Susana França  Miguel Pessanha Pais  Sofia Henriques  Luis Cancela da Fonseca  Henrique N. Cabral 《Estuarine, Coastal and Shelf Science》2011

The importance of estuaries for coastal environments is widely acknowledged but their role, structure and ecological status have been the focus of recent scientific efforts mainly concerning large estuarine areas. In this work we used fish assemblages to establish, for the first time, the functional and ecological role of five small estuarine systems along the Portuguese south and southwest coasts. Our results showed that, at a functional approach, fish communities did not differ between estuaries, and that all systems presented a seasonal pattern in diversity values, ecological and feeding guilds. These small estuaries contribute to the support of coastal fish populations by providing temporary habitats to the critical life stages of marine species, shelter and feeding grounds, and should be considered in an ecological and conservation perspective.  相似文献   

The relationship between the Sérsic law profiles measured along the major and minor axes of elliptical galaxies     

F. Ferrari †  H. Dottori  N. Caon  A. Nobrega  D. B. Pavani ‡ 《Monthly notices of the Royal Astronomical Society》2004,347(3):824-832

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