The annual total and organic mercury bioaccumulation pattern of Scrobicularia plana and Hediste diversicolor was assessed to evaluate the potential mercury transfer from contaminated sediments to estuarine food webs. S. plana was found to accumulate more total and organic mercury than H. diversicolor, up to 0.79 mg kg-1 and 0.15 mg kg-1 (wet weight) respectively, with a maximum annual uptake of 0.21 mg kg-1 y-1, while for methylmercury the annual accumulation was similar between species and never exceeded 0.045 mg kg-1 y-1. The higher organic mercury fraction in H. diversicolor is related to the omnivorous diet of this species. Both species increase methylmercury exposure by burrowing activities and uptake in anoxic, methylmercury rich sediment layers. Integration with the annual biological production of each species revealed mercury incorporation rates that reached 28 [mu]g m-2 y-1, and to extract as much as 11.5 g Hg y-1 (of which 95% associated with S. plana) in the 0.4 km2 of the most contaminated area, that can be transferred to higher trophic levels. S. plana is therefore an essential vector in the mercury biomagnification processes, through uptake from contaminated sediments and, by predation, to transfer it to economically important and exploited estuarine species.; http://www.sciencedirect.com/science/article/B6WDV-4RT4XSB-1/1/99cc738eb589636060fbbdf4f36ad92a
Due to the lack of knowledge regarding annual bioaccumulation rates in estuarine and marine fauna, the main aim of this work was to study the annual mercury bioaccumulation in the well-documented bivalve species Scrobicularia plana along a human induced mercury gradient in the Ria de Aveiro coastal lagoon (Portugal) and in a nearby, non-polluted system (Mondego estuary), parallel to the risks associated with its consumption by humans.; http://www.sciencedirect.com/science/article/B6WDV-4KCPVG3-3/1/4ebba3f9f7a3e11dd49b8124f65c1786
Fonte: Universidade de CoimbraPublicador: Universidade de Coimbra
Tipo: Dissertação de Mestrado
Relevância na Pesquisa
Os ambientes marinhos estão entre os ecossistemas mais importantes do
planeta, tanto em termos ecológicos como sócio-económicos. O estuário do
Mondego, como muitos outros, providencia funções ecológicas essenciais,
serviços e óptimos habitats para muitas espécies e possui extrema importância
para a população humana local. Todos estes benefícios oferecidos por este
ecossistema podem estar em risco, visto que a frequência e a intensidade de
eventos climáticos extremos, tais como cheias e secas, tem vindo a aumentar
drasticamente nas últimas décadas, como resultado das alterações climáticas.
Estas perturbações afectam a qualidade geral do estuário, diminuindo a sua
produtividade através de impactos na abundância e biomassa das populações
e comunidades. O objectivo principal deste estudo foi analisar a resposta de
Scrobicularia plana, uma espécie dominante de bivalves na comunidade
macrobentónica do Mondego, à forte cheia de 2000/2001 e à seca extrema de
2004/2005. Esta espécie foi altamente afectada por estes dois eventos, mas de
diferentes modos. A cheia provocou uma total ausência de recrutamentos em
2001, a diminuição da biomassa e alterou a estrutura da população. A seca
causou um maior impacto na biomassa...
The main goal of the present thesis was to assess the impacts of anthropogenic and natural stressors on the Mondego estuary. In order to achieve this purpose, the ecological responses of the macrobenthic community, and particularly of the bivalve Scrobicularia plana, to multiple stressors and under different ecological scenarios were studied. Focusing on the dynamics and production of macrobenthic assemblages and key species of the estuary is a good evaluation method of the ecological integrity and is important to understand how the ecosystem reacts to
ecological impacts and how it will respond to future changes. The thesis core is
divided in three main chapters, focusing on: 1) the impacts of anthropogenic and
natural stressors on the macrobenthic community and on one of its main components
(bivalves); 2) the ecological behaviour of S. plana under different environmental
scenarios and by the development of a population dynamics model, simulating
eutrophication and restoration conditions; 3) the ecological patterns of several S.
plana populations along its distributional range, intending to assess different life
strategies on populations of the same species.
In Chapter 1, the interactions between eutrophication and intense floods were
Contamination by polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) was investigated along a
spatial gradient in water, sediments and in commercially important bivalve species Scrobicularia plana, from
Ria de Aveiro (Portugal). Organochlorines dissolved in water were below detection limit and concerning
suspended particulate matter, only PCBs were quantified, ranging from 3.8 to 5.8 ng ∙ g−1 DW (Σ13PCBs).
There was a distinct spatial gradient regarding PCB accumulation in sediments. The highest concentrations
were found in deeper layers and closest to the pollution source, decreasing gradually along a 3 km area. Contamination
in sediments exceeded the Canadian and Norwegian sediment quality guidelines, inducing potential
toxic effects in related biota. PCBs tended to bioaccumulate throughout S. plana lifespan but with different
annual rates along the spatial gradient. The maximum values were found in older individuals up to 3+ years
old, reaching 19.4 ng ∙ g−1 DW. HCB concentrations were residual and no bioaccumulation pattern was evident.
Congeners 138, 153 and 180 were the most accumulated due to their abundance and long-term persistence
in the environment. In the inner area of the Laranjo Bay (0.6 km2), the species was able to remove up to
0.4 g of PCBs annually from sediments into their own tissues...
As praias, devido aos processos físicos e geológicos associados ao ambiente
sedimentar, são um dos habitats mais inóspitos para o estabelecimento de
comunidades de macroinvertebrados. No entanto, apesar da sua aparente
uniformidade e pobreza específica, as praias sedimentares possuem uma
fauna marinha de grande diversidade ecológica. A distribuição da macrofauna
nestas praias depende de uma série de respostas quer físicas quer biológicas
ao ambiente, sendo a zonação um fenómeno bem conhecido nos habitats
intertidais. Nas condições relativamente protegidas dos sistemas estuarinos,
as zonas intertidais são caracterizadas pela abundância de matéria orgânica e
pela presença de cadeias tróficas complexas, onde os macroinvertebrados
desempenham um papel fundamental no fluxo de matéria e energia para níveis
tróficos superiores. Neste estudo é realizada a caracterização espaciotemporal
da comunidade de macroinvertebrados bentónicos e dos parâmetros
ambientais numa praia estuarina do Canal de Mira (Ria de Aveiro, NO
Portugal), é estimada a produção secundária anual e são determinadas
relações tróficas entre algumas das espécies mais importantes. A
caracterização espacio-temporal foi efectuada através de uma amostragem
aleatória estratificada sazonal (Abril...
O principal objectivo deste trabalho foi avaliar o nível de contaminação da
Ria de Aveiro por arsénio através da determinação das concentrações de
arsénio nos sedimentos, matéria particulada suspensa (SPM) e água e,
principalmente, avaliar a capacidade do bivalve Scrobicularia plana
(amêijoa) como biomonitor para este contaminante na Ria de Aveiro.
Foram recolhidas amostras de sedimentos, SPM, água e amêijoa de vários
locais na zona do Largo do Laranjo, com base numa análise preliminar que
demonstrou existir um gradiente de contaminação por arsénio nesta zona.
As amêijoas foram divididas em cinco classes etárias com 1 cm de intervalo
(C1 a C5), correspondendo a classes anuais de tamanho. A determinação
do teor de arsénio total em todas as amostras foi efectuada por
espectrometria de fluorescência atómica com geração de hidretos (HGAFS).
Os teores de arsénio presente nos sedimentos, SPM e águas da Ria de
Aveiro apresentaram um gradiente de concentração. Nas águas as
concentrações de arsénio variaram entre 0,5 μg/L no local menos
contaminado e 5,3 μg/L no local mais contaminado, enquanto nos
sedimentos foram encontrados valores superiores a 90 mg/kg no local mais
contaminado e na SPM, os valores atingiram os 260 mg/kg.
As concentrações de arsénio total nas amêijoas apresentam...
This study aimed to test the hypothesis whether mercury (Hg) activates or suppresses inappropriately the immunity of the bivalve Scrobicularia plana inhabiting a Hg contaminated area (Laranjo basin, Ria de Aveiro, Portugal). Immunity endpoints, as well as lipid peroxidation (LPO) as a sign of damage, were evaluated in parallel with total Hg burden. Bivalves from both moderately (MO) and highly (HI) contaminated sites displayed higher haemolymph Hg load and reduced plasma agglutination. Increased haemocytes density and decreased phagocytosis were observed at HI, whereas increased oxidative burst activity (OBA) was observed at MO, pointing out that the immunotoxicity is a result of Hg direct contact involving no ROS intervention. OBA observed at MO was concomitantly associated to peroxidative damage as depicted by LPO increase in haemocytes and haemolymph plasma. Thus, S. plana can be suggested as a suitable bioindicator of metal pollution in coastal areas on the basis of Hg bioaccumulation and immunotoxicity responses.
This study aimed at the assessment of mercury burden and its association to damage vs. antioxidant protection in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age and organ-specific approaches were applied by using different annual size classes (2+, 3+, 4+ and 5+ year old) and assessing specific organs (gills, digestive gland), respectively. Bivalves were collected from moderately and highly contaminated sites at Laranjo basin – Ria de Aveiro (Portugal), where a mercury gradient was identified, and compared with those from a reference site. Besides total and organic mercury accumulation, endpoints combining lipid peroxidation (LPO), as a damage sign, and antioxidant protection (catalase, CAT; glutathione peroxidase, GPX; glutathione S-transferase, GST, activities) were determined. The whole-body accumulation as total mercury changed according to the environmental gradient for all age classes, while in terms of organic mercury, only 5+-year-old animals showed increased accumulation with increased environmental mercury level. Mercury induced peroxidative damage, showing that antioxidative mechanisms were insufficient. The adaptive capacity to pro-oxidant challenge, expressed as antioxidant induction and lesser vulnerability to enzyme inhibition...
The study aimed to assess morphological, structural and compositional alterations in Scrobicularia plana nacre environmentally exposed to mercury in order to seek out the possibility of the assessed alterations as a monitoring tool to handle complexity and interactions of metals in the environment involving a non-invasive methodology. Bivalves were collected from a mercury contaminated site (Laranjo basin – Ria de Aveiro, Portugal) and a reference site in the same aquatic system. The combination of scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS) technique depicted a sheet like morphology of bivalve nacre collected from the reference site. Moreover, EDS plot exhibited the presence of potassium, oxygen, calcium, and carbon elements. Shells collected from the contaminated area depicted lamellar patches like structures with particle like morphology composition. SEM images corresponding to the elemental analysis by EDS plot clearly denoted the presence of mercury. SEM images from the other locations of the contaminated shells depicted large surface area, a broken or ruptured symmetry of organic matrix as well as crack-like gaps. The influence of environmental mercury affecting the surface morphology of S. plana nacre showed dimple like morphology (as proved by transmission electron microscopy...
Mercury is a global priority pollutant and given its huge relevance in terms of environmental damage and a threat to human health, it is important to study the bioaccumulation processes at the level of macrobenthic organisms and evaluate possible consequences for the trophic chain. In this work we evaluate the mercury accumulation rates of two distinct and economically important macrobenthic species, the polychaete Hediste diversicolor and the bivalve Scrobicularia plana, through a mesocosms laboratory experiment.
The present experiment demonstrated different bioaccumulation kinetics for each species: while S. plana has a rapid accumulation after 48 h of exposure to contaminated sediments and then reaches a steady state, H. diversicolor has a linear mercury accumulation throughout the experiment time (31 days). The different patterns observed can be related to different feeding strategies and assimilation efficiencies. In addition, we can conclude that independently of the mercury concentration in the sediments, the two studied species in both contaminated sediments reached the same percentage (25%) of mercury accumulated at the end of the experiment when compared to the maximum concentrations recorded in the field.
This experiment highlights that the mercury bioaccumulation rate by these two economically and ecologically important macrobenthic species is a reasonably rapid process which can promote serious consequences for the higher trophic levels...
The annual total and organic mercury bioaccumulation pattern of Scrobicularia plana and Hediste diversicolor was assessed to evaluate the potential mercury transfer from contaminated sediments to estuarine food webs. S. plana was found to accumulate more total and organic mercury than H. diversicolor, up to 0.79 mg kg−1 and 0.15 mg kg−1 (wet weight) respectively, with a maximum annual uptake of 0.21 mg kg−1 y−1, while for methylmercury the annual accumulation was similar between species and never exceeded 0.045 mg kg−1 y−1. The higher organic mercury fraction in H. diversicolor is related to the omnivorous diet of this species. Both species increase methylmercury exposure by burrowing activities and uptake in anoxic, methylmercury rich sediment layers. Integration with the annual biological production of each species revealed mercury incorporation rates that reached 28 μg m−2 y−1, and to extract as much as 11.5 g Hg y−1 (of which 95% associated with S. plana) in the 0.4 km2 of the most contaminated area, that can be transferred to higher trophic levels. S. plana is therefore an essential vector in the mercury biomagnification processes, through uptake from contaminated sediments and, by predation, to transfer it to economically important and exploited estuarine species.
During a recent intervention in the Mondego River estuary, Portugal, the existing connection between the north and the more eutrophic south arm was enlarged, a nutrient-enriched freshwater input was diverted to the north arm and the remaining seagrass patches were protected from human activity. System restoration did not involve disruption of the sediment and successfully reduced the eutrophic state of the estuary. This provided an excellent opportunity to test a population-dynamics model of a common European estuarine bivalve, Scrobicularia plana, (da Costa, 1778) before and after the intervention. The model simulated the number of individuals in three different sampling stations, before and after system restoration, and is regulated by water temperature, salinity and population density. Our analysis indicated that the occurrence of extreme values of the environmental variables has the strongest effect on the model response and possibly on the real system. The model was calibrated and validated with independent data sets and the model performance was highest under the conditions after the management. This corroborates the notion that system restoration was successful and indicates that the system became more predictable after management.
Salinity is a major factor impacting estuarine organisms, especially in cases of abrupt changes. The increased physiological stress frequently results in behavioral and physiological responses and in extreme cases may lead to mortality episodes. Mortality and behavioral activity of the bivalves Scrobicularia plana and Cerastoderma edule were evaluated under a wide range of salinity values. Specimens were sampled in the Mondego estuary (Portugal), acclimated and exposed to different salinity treatments (0–35) at constant temperature (20 °C). Organisms were fed daily. Mortality and individual activity were registered during 120 h laboratory assays. Both species showed an optimal salinity range for their activity (S. plana: 20–30; C. edule: 20–25), and survival was mainly affected by low salinity (S. plana: LC50120 h = 5.35; C. edule: LC50120 h = 11.09), with 100% mortality under critical values (S. plana: <5; C. edule: <10). Therefore, the occurrence of extreme climate events, especially floods, may in fact severely impact these species through drastic changes in salinity.
Fonte: Universidade de Trás-os-Montes e Alto DouroPublicador: Universidade de Trás-os-Montes e Alto Douro
Tipo: Dissertação de Mestrado
Relevância na Pesquisa
Dissertação de Mestrado em Engenharia Zootécnica; O consumo de oxigénio e a condição corporal foram estudados para um grupo de 30 animais submetidos a um período de jejum. Os animais foram divididos em 5 grupos, 6 indivíduos cada grupo, a temperaturas de 8ºC, 12ºC, 15ºC, 20ºC e 24ºC. Foram colhidas amostras de água e medidas as respectivas concentrações de oxigénio, após 8 horas de consumo, seguindo o procedimento sugerido por Winkler (1888), “Winkler method”. Os dados obtidos foram tratados e submetidos a ANOVA.
Os resultados mostram que o consumo de oxigénio aumenta com o aumento da temperatura. A média de consumo mais elevada foi detectada a 24ºC (5,559 μmol/h) e a mais baixa a 8ºC (0,780 μmol/h). Às temperaturas de 8ºC, 12ºC, 15ºC e 20ºC, as diferenças registadas entre consumos de oxigénio não são significativas. À temperatura de 24ºC, registou-se um pico de consumo de oxigénio ao oitavo dia sem alimento seguido de um abaixamento gradual ao longo do tempo. Tendo em conta a condição da massa corporal (mgAFDM.cm-3), os resultados mostram que a S. plana é afectada pela temperatura. A temperaturas mais altas, a condição de massa corporal dos animais apresenta um decréscimo mais acentuado do que a temperaturas mais baixas...
Dissertação de Mestrado em Engenharia Ciências da Engenharia – Engenharia Zootécnica; The growth and breeding cycle (sex ratio, size at first spawning, spawning season and recruitment) were studied for three populations of Scrobicularia plana (Da Costa, 1778) along the European Coast: Minho, Portugal; Trondheim, Norway and Terneuzen, Netherlands. The Von Bertalanffy growth equation was used to describe growth in S. plana. Using the collected data on shell length, somatic mass and animals age, the growth constant (K) was computed for the three populations. No clear pattern for growth rate related with latitude was observed: the Portuguese population showed a slower growth rate (K=0.268 and K=0.185 for shell growth and somatic growth, respectively), the Dutch showed the highest growth rate (K=0.368 and K=0.478), following by the Norwegian population (K=0.332 and 0.346). In the other hand, reproduction showed a clear pattern related with latitude, with the Portuguese population showing a longer reproductive season than the other two northern populations. A female to male sex ratio of 1.6:1 was registered for Norway, 3.55:1 for the Netherlands and 1.27:1 for Portugal. The Portuguese S. plana reaches sexual maturity at a bigger shell length (the minimum shell length observed was above 25 mm) than the studied northern populations (20.5 mm for the Netherlands and 17.5 mm for Norway). In fact...
Over the last few decades, the excessive growth of macroalgae and decline of seagrass beds, associated with increased eutrophication, has become a worldwide problem. It is known that submersed aquatic vegetation (SAV) offers stable habitats, allowing the continuous availability of food and protection against predators and contributing to biodiversity, sediment stability and water transparency when compared to areas covered by macroalgae mats. In the Mondego estuary (Portugal), several mitigation measures (nutrient-load reduction, seagrass-bed protection and freshwater-circulation enhancement) were implemented in 1998 in order to promote the recovery of the seagrass beds and the entire surrounding environment following a long period of eutrophication. Here the success of this restoration project is evaluated by comparing the water nutrient concentrations, the extent of seagrass cover and the dynamics of the bivalve Scrobicularia plana before and after the implementation of the management measures. During the period in which environmental quality declined, S. plana's adult abundance, total biomass and growth production also declined, parallel with the almost total disappearance of Zostera noltii. After the implementation of management measures...
The present study, carried out in a mercury (Hg) contaminated estuary, aimed to investigate: (i) the long-term evolution of the Hg bioavailability in the environmental matrices, in a period of 5 years (2003–
2008), without new anthropogenic inputs; (ii) the temporal evolution of Hg load (organic and inorganic
forms) in the native bivalve
, inferring the progression of human health risk associated
to its consumption and the dependence on the animals’ size. The area selected was Laranjo basin of Ria de
Aveiro (Portugal), where a Hg gradient was identified because of past discharges from a chlor-alkali plant.
Two sites termed M (moderately contaminated) and H (highly contaminated) were compared with an
uncontaminated reference (R) site. Results displayed a persistence of Hg in the environment, though
the levels in sediment decreased at site H, confirming the ecosystem recovery. The risk associated to clam
consumption remained stable in 2008 considering their total Hg (T-Hg) load and the limits established by
public health authorities, though T-Hg levels significantly decreased at H site for size classes C3 (2 year)
and C4 (4 year). Organic Hg (O-Hg) accumulation increased from 2003 to 2008, reaching threatening lev-
els and suggesting an increased bioavailability of this Hg form. This evolution towards an increase of O-
Hg accumulation was particularly prominent under a moderate contamination scenario (site M). Overall...
This study aimed to investigate the role of non-enzymatic antioxidants on adaptive skills over time in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age (2+, 3+, 4+, 5+ year old) and organ-specific (gills, digestive gland) approaches were applied in bivalves collected from moderately and highly contaminated sites at Ria de Aveiro (Portugal). S. plana's adaptive skills were dependent on the contamination extent; under moderate contamination scenario, the intervention of the different antioxidants took place harmoniously, evidencing an adjustment capacity increasing with the age. Under higher contamination degree, S. plana failed to cope with mercury threat, showing an age-dependent deterioration of the defense abilities. In organ-specific approach, the differences were particularly evident for thiol-compounds, since only gills displayed the potential to respond to moderate levels by increasing non-protein thiols and total glutathione. Under high contamination degree, both organs were unable to increase thiol-compounds, which were compensated by the ascorbic acid elevation.
9 pages, 5 figures, 4 tables; The polychaete worm Nereis diversicolor and the clam Scrobicularia plana were collected from several sites, affected by different types of contamination, in a littoral enclosure in the SW Spain (Caño Sancti-Petri and Rio San Pedro). N. diversicolor was present in 6 sampling sites whereas S. plana in 4 of them. The aim of our study was to relate several pollution biomarkers to chemical sources (metals and organic pollutants e.g. PCB, PAH) in these species, thereby confirming their adequacy as sentinels for this habitat. The biomarkers surveyed in the two invertebrates were the activities of the antioxidant enzyme catalase (CAT), the phase II detoxifying enzyme glutathione S-transferase (GST) and the neurotoxicity marker acetylcholinesterase (AChE). Metallothionein (MT) levels were measured as a biomarker of exposure to metals. The results suggested a different response in the two sediment-dwelling organisms, the sediment-eating polychaete and the water-filtering clam, probably as a consequence of different contamination exposures. The results also suggested that samples from the “Caño Sancti-Petri” were exposed to biologically active compounds that altered some of their biochemical responses. Of all the biomarkers tested...