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.
2020
Authors
Ralf RautenbergerAbstract
The commercial cultivation of marine macroalgae is a young and rapidly growing industry sector in Norway. Although it is currently limited to a few brown macroalgae, other species such as the green marine macroalga Ulva fenestrata (formerly Ulva lactuca) has also a high potential for an industrial biomass production, for example to be used for the food marked. However, this process is strongly affected by the presence of marine diatoms transported along with the seawater into the cultivation system of U. fenestrata. These diatoms not only proliferate in the water tanks, they also colonise the green macroalgal biomass with many brown spots, which reduces its value for the food marked significantly. This presentation shows the results of a project that studied the use of germanium dioxide (GeO2) as a known growth inhibitor of diatoms to control their contamination during the biomass production process of U. fenestrata. First, the co-occurring diatom was morphologically identified as Fragilaria sp. using light microscopy. Thereafter, a dose-response experiment was conducted to reveal the concentrations of GeO2, resulting in an effective growth inhibition of Fragilaria sp. Based on this knowledge, the impact of different GeO2 concentrations was studied on how the photophysiolgy (photosynthetic characteristics, pigment patterns) and growth of U. fenestrata are affected in both small-scale (2 L) and large-scale (100 L) cultivation systems. An effective control of the proliferation of Fragilaria sp. during the cultivation process of U. fenestrata may result in the production a high-quality biomass with a high value for the food marked.
Authors
Serena Lima Peter Simon Claus Schulze Lisa M. Schüler Ralf Rautenberger Daniela Morales-Sanchez Tamára F. Santos Hugo Pereira João C.S. Varela Francesca Scargiali Rene Hubertus Wijffels Viswanath KironAbstract
As the periodic emission of light pulses by light emitting diodes (LEDs) is known to stimulate growth or induce high value biocompounds in microalgae, this flashing light regime was tested on growth and biochemical composition of the microalgae Nannochloropsis gaditana, Koliella antarctica and Tetraselmis chui. At low flashing light frequencies (e.g., 5 and 50 Hz, Duty cycle = 0.05), a strain-dependent growth inhibition and an accumulation of protein, polyunsaturated fatty acids, chlorophyll or carotenoids (lutein, β-carotene, violaxanthin and neoxanthin) was observed. In addition, a 4-day application of low-frequency flashing light to concentrated cultures increased productivities of eicosapentaenoic acid (EPA) and specific carotenoids up to three-fold compared to continuous or high frequency flashing light (500 Hz, Duty cycle = 0.05). Therefore, applying low-frequency flashing light as finishing step in industrial production can increase protein, polyunsaturated fatty acids or pigment contents in biomass, leading to high-value algal products.
Authors
Daniel Liesner Louise Fouqueau Myriam Valero Michael Roleda Gareth A. Pearson Kai Bischof Klaus Valentin Inka BartschAbstract
To understand the thermal plasticity of a coastal foundation species across its latitudinal distribution, we assess physiological responses to high temperature stress in the kelp Laminaria digitata in combination with population genetic characteristics and relate heat resilience to genetic features and phylogeography. We hypothesize that populations from Arctic and cold-temperate locations are less heat resilient than populations from warm distributional edges. Using meristems of natural L. digitata populations from six locations ranging between Kongsfjorden, Spitsbergen (79°N), and Quiberon, France (47°N), we performed a common-garden heat stress experiment applying 15°C to 23°C over eight days. We assessed growth, photosynthetic quantum yield, carbon and nitrogen storage, and xanthophyll pigment contents as response traits. Population connectivity and genetic diversity were analyzed with microsatellite markers. Results from the heat stress experiment suggest that the upper temperature limit of L. digitata is nearly identical across its distribution range, but subtle differences in growth and stress responses were revealed for three populations from the species’ ecological range margins. Two populations at the species’ warm distribution limit showed higher temperature tolerance compared to other populations in growth at 19°C and recovery from 21°C (Quiberon, France), and photosynthetic quantum yield and xanthophyll pigment responses at 23°C (Helgoland, Germany). In L. digitata from the northernmost population (Spitsbergen, Norway), quantum yield indicated the highest heat sensitivity. Microsatellite genotyping revealed all sampled populations to be genetically distinct, with a strong hierarchical structure between southern and northern clades. Genetic diversity was lowest in the isolated population of the North Sea island of Helgoland and highest in Roscoff in the English Channel. All together, these results support the hypothesis of moderate local differentiation across L. digitata's European distribution, whereas effects are likely too weak to ameliorate the species’ capacity to withstand ocean warming and marine heatwaves at the southern range edge.
Authors
Michael Roleda Sandra Lage Daniel Fonn Aluwini Celine Rebours May Bente Brurberg Udo Nitschke Francesco G. GentiliAbstract
The increasing use of seaweeds in European cuisine led to cultivation initiatives funded by the European Union. lactuca, commonly known as sea lettuce, is a fast growing seaweed in the North Atlantic that chefs are bringing into the local cuisine. Here, different strains of Arctic U. lactuca were mass-cultivated under controlled conditions for up to 10 months. We quantified various chemical constituents associated with both health benefits (carbohydrates, protein, fatty acids, minerals) and health risks (heavy metals). Chemical analyses showed that long-term cultivation provided biomass of consistently high food quality and nutritional value. Concentrations of macroelements (C, N, P, Ca, Na, K, Mg) and micronutrients (Fe, Zn, Co, Mn, I) were sufficient to contribute to daily dietary mineral intake. Heavy metals (As, Cd, Hg and Pb) were found at low levels to pose health risk. The nutritional value of Ulva in terms of carbohydrates, protein and fatty acids is comparable to some selected fruits, vegetables, nuts and grains.
Abstract
Pythium species are ubiquitous organisms known to be pathogens to terrestrial plants and marine algae. While several Pythium species (hereafter, Pythium) are described as pathogens to marine red algae, little is known about the pathogenicity of Pythium on marine green algae. A strain of a Pythium was isolated from a taxonomically unresolved filamentous Ulva collected in an intertidal area of Oslo fjord. Its pathogenicity to a euryhaline Ulva intestinalis collected in the same area was subsequently tested under salinities of 0, 15, and 30 parts per thousand (ppt). The Pythium isolate readily infected U. intestinalis and decimated the filaments at 0 ppt. Mycelium survived on U. intestinalis filaments for at least 2 weeks at 15 and 30 ppt, but the infection did not progress. Sporulation was not observed in the infected algal filaments at any salinity. Conversely, Pythium sporulated on infected grass pieces at 0, 15, and 30 ppt. High salinity retarded sporulation, but did not prevent it. Our Pythium isolate produced filamentous non-inflated sporangia. The sexual stage was never observed and phylogenetic analysis using internal transcribed spacer suggest this isolate belongs to the clade B2. We conclude that the Pythium found in the Oslo fjord was a pathogen of U. intestinalis under low salinity.
2019
Authors
Ralf RautenbergerAbstract
No abstract has been registered
Authors
Peter Simon Claus Schulze Celeste Brindley José M. Fernández Ralf Rautenberger Hugo Pereira Rene Hubertus Wijffels Viswanath KironAbstract
Light attenuation in photobioreactors is a major bottleneck in microalgal production. A possible strategy for artificial light-based microalgal production to deliver light deep inside the culture is through the periodical emission of high intensity light flashes (so-called flashing light). However, our results did not show improved photosynthetic rates compared to continuous light for dilute and concentrated Tetraselmis chui cultures exposed to flashing light with various repetition rates (frequencies 0.01 Hz–1 MHz), light-dark ratios (duty cycles: 0.001–0.7) or time-averaged light intensity (50–1000 μmol s−1 m−2). Likewise, flashing light applied to Chlorella stigmatophora and T. chui batch cultures could not enhance growth. However, we observed flashing light effects at different duty cycles and frequencies, depending on cell acclimation, culture concentration, and light intensity. In conclusion, artificial flashing light does not improve microalgal biomass productivities in photobioreactors, but low frequencies (f < 50 Hz) may be still used to improve light harvesting-associated biomolecules production.
Authors
Ralf RautenbergerAbstract
No abstract has been registered
Authors
Edgardo Cruces Ralf Rautenberger Víctor Mauricio Cubillos Eduardo Ramírez‐Kushel Yesenia Rojas‐Lillo Carlos Lara Jaime Andrés Montory Iván GómezAbstract
Species of the genus Ulva (Chlorophyta) are regarded as opportunistic organisms, which efficiently adjust their metabolism to the prevailing environmental conditions. In this study changes in chlorophyll‐a fluorescence‐based photoinhibition of photosynthesis, electron transport rates, photosynthetic pigments, lipid peroxidation, total phenolic compounds and antioxidant metabolism were investigated during a diurnal cycle of natural solar radiation in summer (for 12 h) under two treatments: photosynthetically active radiation (PAR: 400‐700 nm) and PAR+ ultraviolet (UV) radiation (280‐700 nm). In presence of PAR alone, Ulva rigida showed dynamic photoinhibition, and photosynthetic parameters and pigment concentrations decreased with the intensification of the radiation. On the other hand, under PAR+UV condition a substantial decline up to 43% was detected and an incomplete fluorescence recovery, also, P‐I curve values remained low in relation to the initial condition. The phenolic compounds increased their concentration only in UV radiation treatments without showing a correlation with the antioxidant activity. SOD and APX activities increased over 2‐fold respect at initial values during the onset of light intensity. In contrast, CAT increased its activity rapidly in response to the radiation stress to reach maxima at 10:00 h and decreasing during solar. The present study suggests that U. rigida is capability to acclimate to natural radiation stress relies on a concerted action of various physiological mechanisms that act at different times of the day and under different levels of environmental stress.
Abstract
No abstract has been registered