2018
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The UV filtering potential of drop-casted layers of frustules of three diatom species

År: 2018

The UV filtering potential of drop-casted layers of frustules of three diatom species

Su, Y., Lenau, T. A., Gundersen, E., Kirkensgaard, J. J. K., Maibohm, C., Pinti, J. P. A. & Ellegaard, M. 2018 In : Scientific Reports. 8, 10 p., 959

Publication: Research - peer-reviewJournal article – Annual report year: 2018

Diatoms are in focus as biological materials for a range of photonic applications. Many of theseapplications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls) havebeen carried out on single cells. In this study, for the first time, we test the spectral properties of layersof frustules of three diatom species (Coscinodiscus granii, Thalassiosira punctifera and Thalassiosira pseudonana), with special focus on transmission and reflectance in the UV range. The transmittance efficiency in the UV A and B range was: T. pseudonana (56–59%) >C. granii (53–54%) >T. punctifera (18–21%) for the rinsed frustules. To investigate the underlying cause of these differences, we performed X-ray scattering analysis, measurement of layer thickness and microscopic determination of frustule nanostructures. We further tested dried intact cells in the same experimental setup. Based on the sedata we discuss the relative importance of crystal structure properties, nanostructure and quantity of material on the spectral properties of diatom layers. Characterization of the UV protection performance of layers of diatom frustules is of central relevance for their potential use as innovative bio-based UV filters.
Original languageEnglish
Article number959
JournalScientific Reports
Volume8
Number of pages10
ISSN2045-2322
DOIs
StatePublished - 2018

 

Foraging response and acclimation of ambush feeding and feeding-current feeding copepods to toxic dinoflagellates

År: 2018

Copepods exposed to toxic algae in “black box” incubation experiments show highly varied responses, but the mechanisms cannot be revealed from such experiments and the implications to copepod and phytoplankton population dynamics consequently not evaluated. Here, we use direct video observations to examine the response and temporal acclimation (5 d) of two copepods with different foraging behaviors to toxic dinoflagellates. Feeding-current feeding Temora longicornis and ambush feeding Acartia tonsa were offered three strains of toxic Alexandrium tamarense and a nontoxic control Protoceratium reticulatum. We hypothesize (1) that ambush feeders are less affected by toxic algae than feeding-current feeders, (2) that copepods acclimate to the toxic algae, and (3) that phytoplankton cells previously exposed to copepod cues elicit stronger responses. Both copepod species consumed the toxic algae at a reduced rate and there was no difference in their net-response, but the mechanisms differed. T. longicornis responded in strain-specific ways by reducing its feeding activity, by rejecting captured algae, or by regurgitating consumed cells. A. tonsa reduced its consumption rate, jump frequency, and jump distance on all strains of the toxic dinoflagellate, and most so on
copepod-cue induced cells. There was limited acclimation to algal toxins, although some behavioral responses relaxed or intensified during the first one to several days. Mortality rates were low and the various responses, thus, all allow the copepods to survive harmful algal blooms. However, the implications to algal population dynamics are species/strains specific, with only prey selection providing the toxic algae with a competitive advantage
Original languageEnglish
JournalLimnology and Oceanography
ISSN0024-3590
DOIs
StateAccepted/In press - 2018

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Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro-climatic Gradient

År: 2018

Shifts in the Source and Composition of Dissolved Organic Matter in Southwest Greenland Lakes Along a Regional Hydro-climatic Gradient

Osburn, C. L., Anderson, N. J., Stedmon, C. A., Giles, M. E., Whiteford, E. J., Mcgenity, T. J., Dumbrell, A. J. & Underwood, G. J. C. 2018 In : Journal of Geophysical Research: Biogeosciences. 15 p.

Publication: Research - peer-reviewJournal article – Annual report year: 2018

Dissolved organic matter (DOM) concentration and quality were examined from Arctic lakes located in three clusters across south-west (SW) Greenland, covering the regional climatic gradient: cool, wet coastal zone; dry inland interior; and cool, dry ice-marginal areas. We hypothesized that differences in mean annual precipitation between sites would result in a reduced hydrological connectivity between lakes and their catchments and that this concentrates degraded DOM. The DOM in the inland lake group was characterized by a lower aromaticity and molecular weight, a low soil-like fluorescence, and carbon stable isotope (δ13C-DOC) values enriched by ~2‰ relative to the coastal group. DOC-specific absorbance (SUVA254) and DOC-specific soil-like fluorescence (SUVFC1) revealed seasonal and climatic gradients across which DOM exhibited a dynamic we term "pulse-process": Pulses of DOM exported from soils to lakes during snow and ice melt were followed by pulses of autochthonous DOM inputs (possibly from macrophytes), and their subsequent photochemical and microbial processing. These effects regulated the dynamics of DOM in the inland lakes and suggested that if circumpolar lakes currently situated in cool wetter climatic regimes with strong hydrological connectivity have reduced connectivity under a drier future climate, they may evolve toward an end-point of large stocks of highly degraded DOC, equivalent to the inland lakes in the present study. The regional climatic gradient across SW Greenland and its influence on DOM properties in these lakes provide a model of possible future changes to lake C cycling in high-latitude systems where climatic changes are most pronounced.

Original languageEnglish
JournalJournal of Geophysical Research: Biogeosciences
Number of pages15
ISSN2169-8953
DOIs
StateAccepted/In press - 2018

Bibliographical note

©2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

 

Combined effects of microplastics and chemical contaminants on the organ toxicity of zebrafish ( Danio rerio )

År: 2018

Combined effects of microplastics and chemical contaminants on the organ toxicity of zebrafish ( Danio rerio )

Rainieri, S., Conlledo, N., Larsen, B. K., Granby, K. & Barranco, A. 2018 In : Environmental Research. 162, p. 135-143

Publication: Research - peer-reviewJournal article – Annual report year: 2018

Microplastics contamination of the aquatic environment is considered a growing problem. The ingestion of microplastics has been documented for a variety of aquatic animals. Studies have shown the potential of microplastics to affect the bioavailability and uptake route of sorbed co-contaminants of different nature in living organisms. Persistent organic pollutants and metals have been the co-contaminants majorly investigated in this field. The combined effect of microplastics and sorbed co-contaminants in aquatic organisms still needs to be properly understood. To address this, we have subjected zebrafish to four different feeds: A) untreated feed; B) feed supplemented with microplastics (LD-PE 125–250 µm of diameter); C) feed supplemented with 2% microplastics to which a mixture of PCBs, BFRs, PFCs and methylmercury were sorbed; and D) feed supplemented with the mixture of contaminants only. After 3 weeks of exposure fish were dissected and liver, intestine, muscular tissue and brain were extracted. After visual observation, evaluation of differential gene expression of some selected biomarker genes in liver, intestine and brain were carried out. Additionally, quantification of perfluorinated compounds in liver, brain, muscular tissue and intestine of some selected samples were performed. The feed supplemented with microplastics with sorbed contaminants produced the most evident effects especially on the liver. The results indicate that microplastics alone does not produce relevant effects on zebrafish in the experimental conditions tested; on the contrary, the combined effect of microplastics and sorbed contaminants altered significantly their organs homeostasis in a greater manner than the contaminants alone.
Original languageEnglish
JournalEnvironmental Research
Volume162
Pages (from-to)135-143
ISSN0013-9351
DOIs
StatePublished - 2018

2017
 

Overlever discarden?

År: 2017

Overlever discarden?

Karlsen, J. D., Savina, E., Noack, T. & Frandsen, R. P. 2017 24, 50, Fiskeri Tidende

Publication: CommunicationNewspaper article – Annual report year: 2018

Original languageDanish
JournalFiskeri Tidende
Volume24
Issue number50
Pages (from-to)8-9
ISSN0909-7325
StatePublished - 2017