National Institute of Aquatic Resources

Charlottenlund, Denmark

National Institute of Aquatic Resources

Charlottenlund, Denmark
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Hovland E.K.,Norwegian University of Science and Technology | Dierssen H.M.,Norwegian University of Science and Technology | Dierssen H.M.,University of Connecticut | Ferreira A.S.,National Institute of Aquatic Resources | And 2 more authors.
Marine Ecology Progress Series | Year: 2013

A more comprehensive understanding of how ocean temperatures influence coc co - lithophorid production of particulate inorganic carbon (PIC) will make it easier to constrain the effect of ocean acidification in the future. We studied the effect of temperature on Emiliania huxleyi PIC production in the Barents Sea using ocean colour remote sensing data. Gross annual PIC production was calculated for 1998-2011 from SeaWiFS and MODIS data and coupled with results from previous studies to create a time-series from 1979-2011. Using that data, we investigated (1) correlations between various climate indices, models and temperature recordings of the Kola transect, and (2) the dynamics of temperature and PIC production. A strong inverse correlation (r2 = 0.88) was found between the strength of the North Atlantic subpolar gyre (SPG) with a 3 yr lead and major trends in temperatures from the Kola transect. The effect of ocean temperature on PIC production was complex but generally positive, explaining roughly 50% of the annual variability and indicating that rising temperatures in the North Atlantic may favour coccolithophorid PIC production in the Barents Sea. Positive phases of the Atlantic multidecadal oscillation tended to precede PIC blooms by 1 yr. © Inter-Research 2013.

Nash D.R.,Copenhagen University | Als T.D.,University of Aarhus | Als T.D.,National Institute of Aquatic Resources | Boomsma J.J.,Copenhagen University
Insectes Sociaux | Year: 2011

The Alcon blue butterfly (Maculinea alcon) parasitizes the nests of several Myrmica ant species. In Denmark, it uses M. rubra and M. ruginodis, but never M. scabrinodis. To further examine the basis of this specificity and local co-adaptation between host and parasite, the pattern of growth and survival of newly-adopted caterpillars of M. alcon in Myrmica subcolonies was examined in the laboratory. M. alcon caterpillars were collected from three populations differing in their host use, and reared in laboratory nests of all three ant species collected from each M. alcon population. While there were differences in the pattern of growth of caterpillars from different populations during the first few months after adoption, which depended on host ant species and the site from which the ants were collected, there was no evidence of major differences in final size achieved. Survival was, however, much higher in nests of M. rubra than in nests of M. ruginodis and M. scabrinodis, even for caterpillars from a population that is never known to use M. rubra as a host in the field. The caterpillars of M. alcon thus do not show local adaptation in their pattern of growth and survival, but instead show a pattern that may reflect different nestmate recognition abilities of the host ants, related to their sociogenetic organisation. The pattern of observed host ant use in the field seems to result from a combination of differences in local host availability and locally adapted infectivity, modulated by smaller differences in survivorship in the nests of the different host ants. © International Union for the Study of Social Insects (IUSSI) 2011.

Norgaard J.V.,University of Aarhus | Petersen J.K.,National Institute of Aquatic Resources | Torring D.B.,National Institute of Aquatic Resources | Jorgensen H.,University of Aarhus | Laerke H.N.,University of Aarhus
Animal Feed Science and Technology | Year: 2015

Mussels cultured on lines for nine months and harvested in March were boiled to remove shells and processed into a dry meal or a silage acidified by formic acid. Starfish meal was prepared from starfish caught in May, and a starfish juice fraction was obtained by pressing fresh starfish. Commercial fish silage from farmed salmon was also included in the experiment. The standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) was evaluated in a Latin square design with pigs (initial weight 39.3 kg) fitted with a simple T-cannula in the terminal ileum. Diets contained 131-162 g CP/kg and 5. g chromic oxide/kg. Endogenous losses of protein and AA were estimated by feeding an N-free diet. On a dry matter (DM) basis, mussel meal contained 605 g, mussel silage 575. g, starfish meal 700. g, starfish juice 393. g, and fish silage 776 g CP/kg. The ratio of AA to CP ranged from 0.83 to 0.87. The content of crude fat was high in the mussel products (157-161 g/kg DM), and the starfish meal and juice were high in ash (203 and 474 g/kg DM) with one-fourth being calcium. The AID of CP was 0.74, 0.81, 0.70, and 0.61 for mussel meal, mussel silage, starfish meal, and fish silage. The SID of CP was 0.83, 0.87, 0.80, and 0.68 for mussel meal, mussel silage, starfish meal, and fish silage. For both CP and AA digestibility, the lowest (P<0.05) was found in fish silage and the highest (P<0.05) in mussel silage. In conclusion, both mussel and starfish products showed chemical characteristics arguing for their use as feedstuffs in pig diets. Processing into silage rather than meal increased the SID of CP and AA, and both mussel products and starfish meal had greater SID compared to commercial fish silage. © 2015 Elsevier B.V.

PubMed | University of Aarhus, Northwest Iceland Nature Research Center, National Institute of Aquatic Resources and Sudan University of Science and Technology
Type: | Journal: Heredity | Year: 2016

Elucidating barriers to gene flow is important for understanding the dynamics of speciation. Here we investigate pre- and post-zygotic mechanisms acting between the two hybridizing species of Atlantic eels: Anguilla anguilla and A. rostrata. Temporally varying hybridization was examined by analyzing 85 species-diagnostic single-nucleotide polymorphisms (SNPs; F

Loick-Wilde N.,Leibniz Institute for Baltic Sea Research | Dutz J.,National Institute of Aquatic Resources | Miltner A.,Helmholtz Center for Environmental Research | Gehre M.,Helmholtz Center for Environmental Research | And 2 more authors.
Limnology and Oceanography | Year: 2012

Eurytemora affinis (Copepoda) were fed 15N-labeled Rhodomonas salina (Cryptophyta) or 15N-labeled Nodularia spumigena (Cyanobacteria) in excess under controlled laboratory conditions. Zooplankton collected from the Baltic Sea were fed natural phytoplankton amended with 15N-labeled N. spumigena. We quantified the direct incorporation of 15N tracer from N2-fixing N. spumigena (diazotroph nitrogen) and ammonium-utilizing R. salina into the amino acid nitrogen (AA-N) of zooplankton using complementary gas chromatography-combustion-isotope ratio mass spectrometry, gas chromatography-mass spectrometry, and elemental analysis-isotope ratio mass spectrometry approaches. Specific and mass-specific TN and AA-N incorporation rates of the 15N tracers were calculated for zooplankton. Highest incorporation of 15N was found in field zooplankton relying on N. spumigena and in E. affinis relying on R. salina. Lowest incorporation was found in E. affinis relying on N. spumigena. Decreasing specific and mass-specific rates during field experiments possibly were due to food shortage, whereas decreasing rates in E. affinis grazing on R. salina were more likely due to satiation. Specific and mass-specific rates were consistently low in E. affinis when exposed to N. spumigena, suggesting that these animals were reluctant to feed on N. spumigena. Essential isoleucine received most of the diazotroph nitrogen in field zooplankton, while nonessential amino acids received most 15N tracer in E. affinis. N. spumigena was clearly an important amino acid nitrogen source for Baltic Sea zooplankton. © 2012, by the Association for the Sciences of Limnology and Oceanography, Inc.

Hansen B.W.,Roskilde University | Jakobsen H.H.,National Institute of Aquatic Resources | Andersen A.,Technical University of Denmark | Almeda R.,CSIC - Institute of Marine Sciences | And 3 more authors.
Journal of Experimental Biology | Year: 2010

The behavior of the ubiquitous estuarine planktotrophic spionid polychaete larvae Polydora ciliata was studied. We describe ontogenetic changes in morphology, swimming speed and feeding rates and have developed a simple swimming model using low Reynolds number hydrodynamics. In the model we assumed that the ciliary swimming apparatus is primarily composed of the prototroch and secondarily by the telotroch. The model predicted swimming speeds and feeding rates that corresponded well with the measured speeds and rates. Applying empirical data to the model, we were able to explain the profound decrease in specific feeding rates and the observed increase in the difference between upward and downward swimming speeds with larval size. We estimated a critical larval length above which the buoyancy-corrected weight of the larva exceeds the propulsion force generated by the ciliary swimming apparatus and thus forces the larva to the bottom. This modeled critical larval length corresponded to approximately 1 mm, at which, according to the literature, competence for metamorphosis and no more length increase is observed. These findings may have general implications for all planktivorous polychaete larvae that feed without trailing threads. We observed bell shaped particle retention spectra with a minimum prey size of approximately 4 mm equivalent spherical diameter, and we found that an ontogenetic increase in maximum prey size add to a reduction in intra-specific food competition in the various larval stages. In a grazing experiment using natural seawater, ciliates were cleared approximately 50% more efficiently than similar sized dinoflagellates. The prey sizes retainable for P. ciliata larvae covers the microplankton fraction and includes non-motile as well as motile prey items, which is why the larvae are trophically positioned among the copepods and dinoflagellates. Not only do larval morphology and behavior govern larval feeding, prey behavior also influences the feeding efficiency of Polydora ciliata. © 2010. Published by The Company of Biologists Ltd.

Hartvig M.,Copenhagen University | Hartvig M.,Technical University of Denmark | Hartvig M.,Lund University | Andersen K.H.,Technical University of Denmark | Andersen K.H.,National Institute of Aquatic Resources
Theoretical Population Biology | Year: 2013

Species with a large adult-offspring size ratio and a preferred predator-prey mass ratio undergo ontogenetic trophic niche shift(s) throughout life. Trophic interactions between such species vary throughout life, resulting in different species-level interaction motifs depending on the maximum adult sizes and population size distributions. We explore the assembly and potential for coexistence of small communities where all species experience ontogenetic trophic niche shifts. The life-history of each species is described by a physiologically structured model and species identity is characterised by the trait: size at maturation. We show that a single species can exist in two different states: a 'resource driven state' and a 'cannibalistic state' with a large scope for emergent Allee effects and bistable states. Two species can coexist in two different configurations: in a 'competitive coexistence' state when the ratio between sizes at maturation of the two species is less than a predator-prey mass ratio and the resource level is low to intermediate, or in a 'trophic ladder' state if the ratio of sizes at maturation is larger than the predator-prey mass ratio at all resource levels. While there is a large scope for coexistence of two species, the scope for coexistence of three species is limited and we conclude that further trait differentiation is required for coexistence of more species-rich size-structured communities. © 2013 Elsevier Inc.

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