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Detection of a Planktothrix agardhii Bloom in Portuguese Marine Coastal Waters

Publication . Churro, Catarina; Azevedo, Joana; Vasconcelos, Vitor; Duarte Silva, Alexandra

Cyanobacteria blooms are frequent in freshwaters and are responsible for water quality deterioration and human intoxication. Although, not a new phenomenon, concern exists on the increasing persistence, scale, and toxicity of these blooms. There is evidence, in recent years, of the transfer of these toxins from inland to marine waters through freshwater outflow. However, the true impact of these blooms in marine habitats has been overlooked. In the present work, we describe the detection of Planktothrix agardhii, which is a common microcystin producer, in the Portuguese marine coastal waters nearby a river outfall in an area used for shellfish harvesting and recreational activities. P. agardhii was first observed in November of 2016 in seawater samples that are in the scope of the national shellfish monitoring system. This occurrence was followed closely between November and December of 2016 by a weekly sampling of mussels and water from the sea pier and adjacent river mouth with salinity ranging from 35 to 3. High cell densities were found in the water from both sea pier and river outfall, reaching concentrations of 4,960,608 cellsL(-1) and 6810.3 x 10(6) cellsL(-1) respectively. Cultures were also established with success from the environment and microplate salinity growth assays showed that the isolates grew at salinity 10. HPLC-PDA analysis of total microcystin content in mussel tissue, water biomass, and P. agardhii cultures did not retrieve a positive result. In addition, microcystin related genes were not detected in the water nor cultures. So, the P. agardhii present in the environment was probably a non-toxic strain. This is, to our knowledge, the first report on a P. agardhii bloom reaching the sea and points to the relevance to also monitoring freshwater harmful phytoplankton and related toxins in seafood harvesting and recreational coastal areas, particularly under the influence of river plumes.

2017-12Journal article

Open Access

Simple and effective chitosan based films for the removal of Hg from waters: Equilibrium, kinetic and ionic competition

Publication . Rocha, Luciana S.; Almeida, Ângela; Nunes, Cláudia; Henriques, Bruno; Coimbra, Manuel A.; Lopes, Cláudia B.; Silva, Carlos M.; Duarte, Armando C.; Pereira, Eduarda

The efficiency of chitosan cross-linked with genipin (Chg) and cross-linked with genipin and grafted with caffeic acid (Ch(g+car)) to remove Hg(II) from waters was investigated. An optimal dose of 50 mg L-1 for both chitosan films was selected based on the equilibrium removal percentage and on the contact time required to attain the equilibrium. The sorption extent was dependent on the initial Hg(II) concentration (C-Hg,C-0), with removal efficiencies varying between 79% and 82% for C-Hg,C-0 = 0.05 mg L-1 and between 89% and 94% for C-Hg,C-0 = 0.50 mg L-1. Under ion competition, the Ch(g) and Ch(g+caf) films showed to be effective and selective for mercury in multimetallic solutions containing also cadmium and lead. In the case of natural river and seawaters, the mercury speciation played an important role in the overall sorption process, reducing the percentage removal of Hg. In terms of modeling, the kinetic data were well described by pseudo-first and pseudo-second order models, depending on the experimental conditions. The diffusion models suggested that the entire sorption process of Hg(II) by both Chg and Chg+caf films was essentially controlled by pore diffusion. The equilibrium data were well described by the Sips isotherm, and the estimated capacity was 2.2 and 4.0 mg g(-1) for Chg and Ch(g+caf) films, respectively. In the whole, the results showed that the sorption efficiency was improved by grafting caffeic acid to the polymeric chains of chitosan cross-linked with genipin. (C) 2016 Elsevier B.V. All rights reserved.

2016-09Journal article

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European Sea Bass (Dicentrarchus labrax) immune status and disease resistance are impaired by arginine dietary supplementation

Publication . Azeredo, Rita; Perez-Sanchez, Jaume; Sitja-Bobadilla, Ariadna; Fouz, Belen; Tort, Lluis; Aragao, Claudia; Oliva-Teles, Aires; Costas, Benjamin

Infectious diseases and fish feeds management are probably the major expenses in the aquaculture business. Hence, it is a priority to define sustainable strategies which simultaneously avoid therapeutic procedures and reinforce fish immunity. Currently, one preferred approach is the use of immunostimulants which can be supplemented to the fish diets. Arginine is a versatile amino acid with important mechanisms closely related to the immune response. Aiming at finding out how arginine affects the innate immune status or improve disease resistance of European seabass (Dicentrarchus labrax) against vibriosis, fish were fed two arginine-supplemented diets (1% and 2% arginine supplementation). A third diet meeting arginine requirement level for seabass served as control diet. Following 15 or 29 days of feeding, fish were sampled for blood, spleen and gut to assess cell-mediated immune parameters and immune-related gene expression. At the same time, fish from each dietary group were challenged against Vibrio anguillarum and survival was monitored. Cell-mediated immune parameters such as the extracellular superoxide and nitric oxide decreased in fish fed arginine-supplemented diets. Interleukins and immune-cell marker transcripts were down-regulated by the highest supplementation level. Disease resistance data were in accordance with a generally depressed immune status, with increased susceptibility to vibriosis in fish fed arginine supplemented diets. Altogether, these results suggest a general inhibitory effect of arginine on the immune defences and disease resistance of European seabass. Still, further research will certainly clarify arginine immunomodulation pathways thereby allowing the validation of its potential as a prophylactic strategy.

2015-10Journal article

Open Access

Benthic food webs support the production of sympatric flatfish larvae in estuarine nursery habitat

Publication . Dias, Ester; Morais, Pedro; Faria, Ana M.; Antunes, C.; Hoffman, Joel C.

Identifying nursery habitats is of paramount importance to define proper management and conservation strategies for flatfish species. Flatfish nursery studies usually report upon habitat occupation, but few attempted to quantify the importance of those habitats to larvae development. The reliance of two sympatric flatfish species larvae, the European flounder Platichthys flesus and the common sole Solea solea, on the estuarine food web (benthic versus pelagic), was determined through carbon and nitrogen stable isotope analysis. The organic matter sources supporting the production of P.flesus and S.solea larvae biomass originates chiefly in the benthic food web. However, these species have significantly different C-13 and N-15 values which suggest that they prey on organisms that use a different mixture of sources or assimilate different components from similar OM pools (or both).

2017-07Journal article

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Climate change impacts on seagrass meadows and macroalgal forests: an integrative perspective on acclimation and adaptation potential

Publication . Duarte, Bernardo; Martins, Irene; Rosa, Rui; Matos, Ana R.; Roleda, Michael Y.; Reusch, Thorsten B. H.; Engelen, Aschwin; Serrao, Ester; Pearson, Gareth; Marques, João C.; Caçador, Isabel; Duarte, Carlos M.; Jueterbock, Alexander

Marine macrophytes are the foundation of algal forests and seagrass meadows-some of the most productive and diverse coastal marine ecosystems on the planet. These ecosystems provide nursery grounds and food for fish and invertebrates, coastline protection from erosion, carbon sequestration, and nutrient fixation. For marine macrophytes, temperature is generally the most important range limiting factor, and ocean warming is considered the most severe threat among global climate change factors. Ocean warming induced losses of dominant macrophytes along their equatorial range edges, as well as range extensions into polar regions, are predicted and already documented. While adaptive evolution based on genetic change is considered too slow to keep pace with the increasing rate of anthropogenic environmental changes, rapid adaptation may come about through a set of non-genetic mechanisms involving the functional composition of the associated microbiome, as well as epigenetic modification of the genome and its regulatory effect on gene expression and the activity of transposable elements. While research in terrestrial plants demonstrates that the integration of non-genetic mechanisms provide a more holistic picture of a species' evolutionary potential, research in marine systems is lagging behind. Here, we aim to review the potential of marine macrophytes to acclimatize and adapt to major climate change effects via intraspecific variation at the genetic, epigenetic, and microbiome levels. All three levels create phenotypic variation that may either enhance fitness within individuals (plasticity) or be subject to selection and ultimately, adaptation. We review three of the most important phenotypic variations in a climate change context, including physiological variation, variation in propagation success, and in herbivore resistance. Integrating different levels of plasticity, and adaptability into ecological models will allow to obtain a more holistic understanding of trait variation and a realistic assessment of the future performance and distribution of marine macrophytes. Such multi-disciplinary approach that integrates various levels of intraspecific variation, and their effect on phenotypic and physiological variation, is of crucial importance for the effective management and conservation of seagrasses and macroalgae under climate change.

2018Journal article

Open Access