2017
 

Integration of fisheries into marine spatial planning: Quo vadis?

År: 2017

Integration of fisheries into marine spatial planning: Quo vadis?

Janssen, H., Bastardie, F., Eero, M., Hamon, K., Hinrichsen, H. H., Marchal, P., Nielsen, J. R., Pape, O. L., Schulze, T., Simons, S., Teal, L. R. & Tidd, A. 2017 In : Estuarine, Coastal and Shelf Science.

Publication: Research - peer-reviewJournal article – Annual report year: 2017

Original languageEnglish
JournalEstuarine, Coastal and Shelf Science
ISSN0272-7714
DOIs
StateAccepted/In press - 2017

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Swimming and feeding of mixotrophic biflagellates

År: 2017

Swimming and feeding of mixotrophic biflagellates

Dölger, J., Nielsen, L. T., Kiørboe, T. & Andersen, A. P. 2017 In : Scientific Reports. 7, 10 p., 39892

Publication: Research - peer-reviewJournal article – Annual report year: 2017

Many unicellular flagellates are mixotrophic and access resources through both photosynthesis and prey capture. Their fitness depends on those processes as well as on swimming and predator avoidance. How does the flagellar arrangement and beat pattern of the flagellate affect swimming speed, predation risk due to flow-sensing predators, and prey capture? Here, we describe measured flows around two species of mixotrophic, biflagellated haptophytes with qualitatively different flagellar arrangements and beat patterns. We model the near cell flows using two symmetrically arranged point forces with variable position next to a no-slip sphere. Utilizing the observations and the model we find that puller force arrangements favour feeding, whereas equatorial force arrangements favour fast and quiet swimming. We determine the capture rates of both passive and motile prey, and we show that the flow facilitates transport of captured prey along the haptonema structure. We argue that prey capture alone cannot fulfil the energy needs of the observed species, and that the mixotrophic life strategy is essential for survival.
Original languageEnglish
Article number39892
JournalScientific Reports
Volume7
Number of pages10
ISSN2045-2322
DOIs
StatePublished - 2017

Bibliographical note

This work is licensed under a Creative Commons Attribution 4.0 International License

 

Bridging the gap between morphological species and molecular barcodes - Exemplified by loricate choanoflagellates

År: 2017

Bridging the gap between morphological species and molecular barcodes - Exemplified by loricate choanoflagellates

Frank, N., Thomsen, H. A. & Daniel J, R. 2017 In : European Journal of Protistology. 57, p. 26-37

Publication: Research - peer-reviewJournal article – Annual report year: 2017

Translating the vast amounts of molecular barcodes from global surveys of microbial eukaryotes into ecological insight depends critically on a well-curated reference database with adequate taxonomic coverage. In this respect, the choanoflagellates resemble other eukaryotic lineages: reasonable coverage at higher taxonomic levels, but missing diversity at the species level. The acanthoecid (loricate) choanoflagellates are well-characterized morphologically, with over 115 species described, but less than 10% with any sequence data. Because lorica shape is species-specific, the acanthoecids represent an opportunity to link morphological with molecular data within a lineage of eukaryotes. To match morphospecies to sequences, we sampled the Kattegat and the Isefjord in Denmark in September 2014 and February 2015. We identified 45 morphospecies and sequenced ribosomal DNA of nine previously unsequenced species, roughly doubling the number of acanthoecid species with sequence data, including the first data representing five genera: Bicosta, Calliacantha, Cosmoeca, Crinolina and Pleurasiga. Our phylogenetic analysis is mainly congruent with morphology-based systematics. Five of the newly sequenced species match a previously unidentified barcode from Tara Oceans, providing access to the global distribution of species isolated from Danish waters. One species, Calliacantha natans, is the second most globally abundant choanoflagellate present in Tara Oceans. Our project translating new ribosomal DNA sequences to distributions of described species on a global scale supports the approach linking morphology to molecular barcodes for microbial eukaryote ecology.
Original languageEnglish
JournalEuropean Journal of Protistology
Volume57
Pages (from-to)26-37
ISSN0932-4739
DOIs
StatePublished - 2017

 

Influence of fixed and moving bed biofilters on micro particle dynamics in a recirculating aquaculture system

År: 2017

Accumulation of fine particulate organic matter in recirculating aquaculture systems (RAS) is a balancebetween system input (from feed to waste), internal transformation, removal and dilution. The mecha-nisms leading to fine particle accumulation in RAS are not fully understood, and neither is the potentialinfluence of biofilters in this aspect.This study describes the effect of fixed bed biofilters (FBB) and moving bed biofilters (MBB) on particlesize distribution and organic matter. It was conducted in an 8.5 m3RAS with four equal biofilters −two FBB and two MBB. The RAS was stocked with rainbow trout (Oncorhynchus mykiss), and operatedunder constant feed loading conditions (1 kg feed/m3of make-up water) for more than three months.Production or removal of micro particles according to biofilter mode of operation (FBB vs. MBB) wasassessed by operating all biofilters simultaneously as well as separately.In periods where FBB and MBB effects were assessed separately, particle concentration was reduced byapproximately 195 particles/mL (from 1117 to 922 particles/mL) per passage through FBB, and increasedby 252 particles (from 2409 to 2667 particles/mL) per passage through MBB. In FBB, a 10% reductionin particle concentration also represented a 10% reduction in total particle surface area and particlevolume. In MBB, a 10% increase in particle concentration also represented a 10% increase in total particlesurface area, but had no effect on total particle volume. A volumetric reduction of particles >100 m,and an equivalent volumetric increase of particles <40 m, showed that MBB produced fine particles bydisintegration of larger particles. A constant removal of particulate volume through all size classes byFBB demonstrates their function as secondary particle removal units.Net removal of organic matter (ConcentrationIN− ConcentrationOUT), as biochemical oxygen demandafter 5 days (BOD5), occurred at the same rates in both modes of operation. While FBB removed a higheramount of filtered BOD5(material filtered through a 1.6 m filter) than MBB, MBB removed more par-ticulate BOD5(Particulate = Raw − Filtered) than FBB, presumably due to disintegration of particles inMBB. In the RAS, ammonia and nitrite were observed at concentrations below 0.20 mg N/L throughoutthe majority of the experiment. However, during the phase where only MBB were in operation, TAN(Total Ammonia Nitrogen) and nitrite levels increased significantly. Nitrate levels ranged between 40and 44 mg N/L, reflecting stable operating conditions and constant feed loading.The trends observed when FBB or MBB were operated separately were also observed when all filterswere operated simultaneously. Differences in biofilm formation, development and maintenance, coupledto reactor flow characteristics are discussed in relation to the fate of micro particles and organic matterwhen operating fixed or moving bed biofilters in RAS
Original languageEnglish
JournalAquacultural Engineering
ISSN0144-8609
StateE-pub ahead of print - 2017