Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2018
Authors
Bernardo Duarte Irene Martins Rui Rosa Ana R. Matos Michael Roleda Thorsten B. H. Reusch Aschwin H. Engelen Ester A. Serrão Gareth A. Pearson João C. Marques Isabel Caçador Carlos M. Duarte Alexander Oliver JüterbockAbstract
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.
Authors
Pablo P. Leal Catriona L. Hurd Sylvia G. Sander Evelyn Armstrong Pamela A. Fernández Tim J. Suhrhoff Michael RoledaAbstract
Ocean warming (OW), ocean acidification (OA) and their interaction with local drivers, e.g., copper pollution, may negatively affect macroalgae and their microscopic life stages. We evaluated meiospore development of the kelps Macrocystis pyrifera and Undaria pinnatifida exposed to a factorial combination of current and 2100-predicted temperature (12 and 16 °C, respectively), pH (8.16 and 7.65, respectively), and two copper levels (no-added-copper and species-specific germination Cu- EC50). Meiospore germination for both species declined by 5–18% under OA and ambient temperature/ OA conditions, irrespective of copper exposure. Germling growth rate declined by >40%·day−1, and gametophyte development was inhibited under Cu-EC50 exposure, compared to the no-added-copper treatment, irrespective of pH and temperature. Following the removal of copper and 9-day recovery under respective pH and temperature treatments, germling growth rates increased by 8–18%·day−1. The exception was U. pinnatifida under OW/OA, where growth rate remained at 10%·day−1 before and after copper exposure. Copper-binding ligand concentrations were higher in copper-exposed cultures of both species, suggesting that ligands may act as a defence mechanism of kelp early life stages against copper toxicity. Our study demonstrated that copper pollution is more important than global climate drivers in controlling meiospore development in kelps as it disrupts the completion of their life cycle.
Authors
Pierrick Francois Denis Stévant Erlend Indergård Aðalheiður Ólafsdóttir Hélène Marfaing Wenche Merete Emblem Larssen Joël Fleurence Michael Roleda Turid Rustad Rasa Slizyte Tom Ståle NordtvedtAbstract
The effects of convective air-drying at 25, 40, and 70 °C and freeze-drying on the quality of the edible kelp Saccharina latissima to be used for food were investigated. Based on the analysis of the carbohydrate and amino acid profiles, as well as polyphenol, fucoxanthin, and ash contents, no significant differences were detected among sample groups, and air-drying up to 70 °C results in equally nutritious products at shorter processing times. Only the iodine content was found lower in freeze-dried compared to air-dried samples. The swelling capacity of the air-dried samples was significantly lower than in freeze-dried samples, particularly at high temperatures (40 and 70 °C), reflecting alteration of the physico-chemical properties of the seaweed during air-drying (attributed to product shrinkage) and reduced capacity of the final product to rehydrate. Structural differences between air-dried products at 25 and 70 °C may explain the differences in mouthfeel perception (dissolving rate) among the two sample groups observed during a sensory evaluation. Overall, the drying temperature within this range did not alter neither the aroma (i.e. odor) nor the flavor intensity of the product. In food applications where the product’s mechanical properties (e.g. porosity) are essential, freeze-drying, and to a lesser extent, air-drying at low temperatures, will result in higher quality products than air-drying at higher temperatures.
Abstract
A series of semi-continuous incubation experiments were conducted with the coccolithophore Emiliania huxleyi strain NIWA1108 (Southern Ocean isolate) to examine the effects of five environmental drivers (nitrate and phosphate concentrations, irradiance, temperature, and partial pressure of CO2 (pCO2// on both the physiological rates and elemental composition of the coccolithophore. Here, we report the alteration of the elemental composition of E. huxleyi in response to the changes in these environmental drivers. A series of dose–response curves for the cellular elemental composition of E. huxleyi were fitted for each of the five drivers across an environmentally representative gradient. The importance of each driver in regulating the elemental composition of E. huxleyi was ranked using a semiquantitative approach. The percentage variations in elemental composition arising from the change in each driver between present-day and model-projected conditions for the year 2100 were calculated. Temperature was the most important driver controlling both cellular particulate organic and inorganic carbon content, whereas nutrient concentrations were the most important regulator of cellular particulate nitrogen and phosphorus of E. huxleyi. In contrast, elevated pCO2 had the greatest influence on cellular particulate inorganic carbon to organic carbon ratio, resulting in a decrease in the ratio. Our results indicate that the different environmental drivers play specific roles in regulating the elemental composition of E. huxleyi with wide-reaching implications for coccolithophore-related marine biogeochemical cycles, as a consequence of the regulation of E. huxleyi physiological processes.
Abstract
No abstract has been registered
Authors
Michael Roleda Jorunn Skjermo Hélène Marfaing Rosa Jonsdottir Celine Rebours Anna Gietl Dagmar B. Stengel Udo NitschkeAbstract
This study represents a large-scale investigation into iodine contents in three commercially important and edible seaweed species from the North Atlantic: the brown algae Saccharina latissima and Alaria esculenta, and the red alga Palmaria palmata. Variability among and within species were explored in terms of temporal and spatial variations in addition to biomass source. Mean iodine concentration in bulk seaweed biomass was speciesspecific: Saccharina > Alaria > Palmaria. Iodine contents of Saccharina biomass were similar between years and seasons, but varied significantly between sampling locations and biomass sources. In Alaria and Palmaria, none of the independent variables examined contributed significantly to the small variations observed. Our data suggest that all three species are rich sources of iodine, and only 32, 283, or 2149 mg dry weight of unprocessed dry biomass of Saccharina, Alaria, or Palmaria, respectively, meets the recommended daily intake levels for most healthy humans.
Authors
Málfríður Bjarnadóttir Björn Viðar Aðalbjörnsson Anna Nilsson Rasa Slizyte Michael Roleda Guðmundur Óli Hreggviðsson Ólafur H. Friðjónsson Rósa JónsdóttirAbstract
The red seaweed Palmaria palmata has previously been reported to have high protein content high in essential amino acids. To extract the proteins a rigid cell wall consisting mainly of β-(1→4)/β-(1→3)-D-xylans must be disrupted. Different methods have been used to overcome this problem along with various methods used for protein evaluation. In this study, the effect of enzymatic pre-treatment on protein extraction was examined. Both enzymatic hydrolysis with xylanase and protease were tested. The amino acid content of the fractions was examined after extraction. The amino acid composition was similar to what has previously been reported; P. palmata was high in essential amino acids. Accordingly, a nitrogen-to-protein conversion factor was calculated for each fraction individually and protein results were compared with calculation using the proximate 6.25 conversion factor. The nitrogen-to-protein conversion factor varied between fractions but all factors were significantly lower than the popularly used 6.25 indicating that this conversion factor for processed P. palmata is effectively and considerably overestimating the protein content. Enzymatic pre-treatment with xylanase resulted in enhanced amino acid content and successful protein extraction. Enzymatic hydrolysis using protease resulted in higher protein content in the liquid extract compared to hydrolysis with xylanase, due to the release of proteins, peptides, and amino acids. Therefore, hydrolysis with protease is not suitable to extract proteins from P. palmata with the method described within this study but might be an optimal method to examine the bioactivity by extracting the protein hydrolysates. However, the result from this study confirm that hydrolysis with xylanase is a feasible choice to extract proteins of good quality from P. palmata.
Authors
Inga Marie Aasen Ingrid Sandbakken Rasa Slizyte Michael Roleda Jorunn Skjermo Åshild KrogdahlAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Michael Roleda Hélène Marfaing Natasa Desnica Rósa Jónsdóttir Jorunn Skjermo Celine Rebours Udo NitschkeAbstract
Seaweeds are increasingly used in European cuisines due to their nutritional value. Many algal constituents, such as polyphenols, are important antioxidants and thus considered beneficial to humans. However, many seaweed species can accumulate heavy metals and exhibit potential health risks upon ingestion. We investigated temporal and spatial variations in polyphenol and heavy metal (As, Cd, Hg, Pb) concentrations of three edible seaweed species. The brown algae Saccharina latissima and Alaria esculenta, and the red alga Palmaria palmata were sourced from natural populations and aquaculture in the NE Atlantic and processed as bulk biomass mimicking industrial scales. The mean polyphenol content was species-specific (Alaria > Saccharina > Palmaria), and highest in winter (for Alaria and Saccharina) and spring (for Palmaria); inter-annual and spatial variations were marginal. Heavy metal concentrations varied between species and depended on collection site, but seasonal variations were minimal. Our data suggest that all three species are good sources of antioxidants, and the heavy metal concentrations are below the upper limits set by the French recommendation and the EU Commission Regulation on contaminants in foodstuffs. A health risk assessment indicated that consumption of these seaweed species poses a low risk for humans with regard to heavy metals. However, an EU-wide regulation on maximal concentration of heavy metals in seaweeds should be established.