Macroalgae, in particular kelps, produce a large amount of biomass in Kongsfjorden, which is to a great extent released into the water in an annual cycle. As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 %... more
Macroalgae, in particular kelps, produce a large amount of biomass in Kongsfjorden, which is to a great extent released into the water in an annual cycle. As an example, the brown alga Alaria esculenta loses its blade gradually, 3 ± 0.8 % of the blade area per day (August 2012), thereby adding to the pool of particulate organic matter (POM) in the fjord. Upon release small thallus pieces are "aging" in that they are prone to leaching and serving as substrate for microorganisms, thus turning into palatable food for suspension and bottom feeders. In order to define a macroalgal baseline for the Kongsfjorden food web, stable isotopes d14C and d15N were measured in individuals of A. esculenta, Saccharina latissima and Laminaria digitata directly sampled after collection and in artificially produced POM (aPOM) of A. esculenta that was allowed to age under experimental conditions. In aPOM from this species sampled in August 2012 the C/N ratios decreased between d1 and d8 of a 14-day culture period in parallel to the fading photosynthetic activity of the algal fragments as demonstrated by use of an Imaging-PAM. Microscopic observations of the aPOM in August 2012 and 2013 revealed the frequent occurrence of small brown algal endo- and epiphytes. First feeding experiments with Mysis oculata (Mysids) and Hiatella arctica (Bivalves) showed that these species can ingest macroalgal POM. The importance of kelp-derived POM for the food web is subject of the current research.
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Despite an Asian aquaculture tradition of many centuries, aquatic farming on the global scale is still a young sector of food production that has grown rapidly in the last 50 years. Seaweeds, a colloquial but widely used term for... more
Despite an Asian aquaculture tradition of many centuries, aquatic farming on the global scale is still a young sector of food production that has grown rapidly in the last 50 years. Seaweeds, a colloquial but widely used term for macroalgae, play an important role in this business which remains a growing, vibrant, and important production sector for healthy human food. As archaeological investigations in Chile testified, seaweeds have been used by humans for about 14,000 years (Dillehay et al. 2008). According to earliest written records, they were consumed in Japan during the Asukaand Nara Era approx. 1,500 years ago. Even food products directly made from seaweeds have a long
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Research Interests: Scanning Electron Microscopy, Immunohistochemistry, Transmission Electron Microscopy, Somatostatin, Hippocampus, and 12 moreCerebral Cortex, Animals, Medical Physiology, Astrocytes, Ultrastructure, Rats, Rat, Glial Fibrillary Acidic Protein, Cytochemistry, Binding Site, Colloidal Gold, and Telencephalon
Moulting and growth as a key aspect of the life-history of crustaceans has been reviewed here for Meganyctiphanes norvegica. Moulting is a cyclical process with relatively constrained, uniform phases that have been well documented. The... more
Moulting and growth as a key aspect of the life-history of crustaceans has been reviewed here for Meganyctiphanes norvegica. Moulting is a cyclical process with relatively constrained, uniform phases that have been well documented. The crustacean moult cycle has a large influence on growth-rates, reproduction and metabolism. Moult and growth are under hormonal control with further environmental influences. A pre-requisite for intensive studies is a detailed moult staging system. Here, a further refinement and temporal phasing is presented for M. norvegica. On such a basis, the dynamics of cuticle synthesis and degradation are shown. Moult and reproductive cycles are interlinked and krill is able to combine growth and reproduction in a way that allows females to achieve similar net growth rates to males. A synchronisation of physiological processes and behaviour related to growth and reproduction enhances environmental success. Moult staging can also be used to assess growth rates in the field. Some further technical approaches are reviewed. Laboratory maintenance and field data are combined to determine growth rates under various environmental conditions. These are related to life-growth assessments from population studies comparing krill along a latitudinal gradient. Life-cycle and physiological data indicate that Northern krill are able to cope with both warm and cold environments and have highly adaptable phenotypes. The species may serve as useful indicator of environmental change. Its potential proliferation in new environments may also have implications to regional food webs, given the krill's high level of growth and productivity and their pivotal trophic role.
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Research Interests: Oceanography and Sea
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The ultrastructure of euphausiid integument was examined in relation to the moult cycle and supplemented by investigations of chitinase activity in the integument and content of N-acetyl-ß-D-glucosamine in the hemolymph. The Antarctic... more
The ultrastructure of euphausiid integument was examined in relation to the moult cycle and supplemented by investigations of chitinase activity in the integument and content of N-acetyl-ß-D-glucosamine in the hemolymph. The Antarctic krill, Euphausia superba was collected in 1983 in Admiralty Bay, King George Island, Antarctica. Some specimens of the Northern krill, Meganyctiphanes norvegica, from the Danish Kattegat served for comparison. As a major aim of the study, the moult staging system developed for living tissue could be verified by ultrastructural findings. Under experimental high production conditions of the Antarctic summer, no period of rest or “intermoult” between post- and premoult was observed in subadult E. superba. Neither was a resting phase seen at the cellular level, the epidermis remained active. The epidermal gland cells did not show any cyclical changes, and the organelles of protein synthesis were generally well developed in all moult stages. In order to follow the physiological course of events, structural and biochemical methods were combined and showed as a result that the last moult stage before ecdysis is characterized by massive cuticular resorption. The epicuticle remained ultrastructurally unchanged before and after ecdysis, even though its permeability should alter at ecdysis. The existence of muscle insertions which connect the old and the new cuticle across the exuvial space suggests an answer to the question why E. superba is hardly impaired in swimming almost up to the time of ecdysis.
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ABSTRACT
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Diel vertical migration of a stable and well-defined population of Nordic krill,Meganyctiphanes norvegica (Crustacea, Euphausiacea) was investigated during eight days in August 1989, in the Ls-Deep, East of the Danish island Ls. Net... more
Diel vertical migration of a stable and well-defined population of Nordic krill,Meganyctiphanes norvegica (Crustacea, Euphausiacea) was investigated during eight days in August 1989, in the Ls-Deep, East of the Danish island Ls. Net catches with a multi-net (MOCNESS) and measurements with a moored and a shipboard Acoustic Doppler Current Profiler (ADCP) were compared. Backscattered energy as a measure for biomass