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C. Tracy Shaw - One of the best experts on this subject based on the ideXlab platform.
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Physical and biochemical properties of the euphausiids Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes in the eastern Bering Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2012Co-Authors: H. Rodger Harvey, Rachel L. Pleuthner, Evelyn J. Lessard, Megan J. Bernhardt, C. Tracy ShawAbstract:Euphausiids are an integral part of the Bering Sea ecosystem, linking primary production to upper level trophic levels as both consumers and prey. Species native to this region extend over a range of geographic provinces and serve as a critical component of the movement of energy through the food web. As one facet of the BEST-BSIERP Bering Sea program, we determined the proximate composition and essential allometric relationships of multiple species of euphausiids collected over three years in the eastern Bering Sea. Three euphausiid species were examined: Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes. While the three species were similar with respect to size, T. inermis had the highest average wet and dry weights per size class, as well as highest carbon and caloric concentrations. Among the three species, T. inermis and T. longipes had similar lipid concentrations, with T. longipes showing higher average lipid concentrations. Empirical equations were developed to describe fundamental relationships between length, weight, PC/PN, and calorie and lipid content for the three species over the full range of sizes encountered in the study area. Such relationships increase our understanding of how euphausiids contribute to the carbon budget and energy input in the eastern Bering Sea system and help to define realistic parameters for ongoing and future modeling efforts.
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The timing and location of spawning for the Euphausiid Thysanoessa spinifera off the Oregon coast, USA
Deep-sea Research Part Ii-topical Studies in Oceanography, 2009Co-Authors: Leah R. Feinberg, William T. Peterson, C. Tracy ShawAbstract:Abstract Thysanoessa spinifera eggs were sampled biweekly from 1997–2005 along a transect extending off the coast of Newport, OR, USA. T. spinifera eggs were typically found in greatest abundance at NH05, our shallower mid-shelf station, and in lowest abundance at NH25, our offshore, deep-water station beyond the shelf break. In most years small peaks in density of T. spinifera eggs were found in late winter (February–March) and/or spring (April–May) along with large, prolonged peaks in summer, from July–September. However, it was more common to find egg densities of −3 or to find no eggs at all (58–91% of sampling dates per year had densities −3 at NH05). We found that egg densities were significantly positively correlated with chlorophyll a concentrations during the winter and spring ( r 2 =0.52 and 0.55 respectively, p When winters were stormy, as in 1998, 1999 and 2000 the first eggs of Thysanoessa spinifera were not observed at any station until after upwelling was initiated later in the spring. However, in other years eggs were likely to be found earlier in the year if there were fewer storms, or winter or spring upwelling events that were not followed by a large storm. In most years, spawning continued until the upwelling season ended in the autumn, however this trend ceased in 2003–2005 and spawning was interrupted earlier in the season. Overall, we found that chlorophyll a peaks and egg peaks increased in magnitude in the later part of our study. We have concluded that T. spinifera is likely an intermittent spawner, whose ovaries are not constantly mature and prepared for spawning, despite the presence of ocean conditions that are suitable for spawning.
H. Rodger Harvey - One of the best experts on this subject based on the ideXlab platform.
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Physical and biochemical properties of the euphausiids Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes in the eastern Bering Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2012Co-Authors: H. Rodger Harvey, Rachel L. Pleuthner, Evelyn J. Lessard, Megan J. Bernhardt, C. Tracy ShawAbstract:Euphausiids are an integral part of the Bering Sea ecosystem, linking primary production to upper level trophic levels as both consumers and prey. Species native to this region extend over a range of geographic provinces and serve as a critical component of the movement of energy through the food web. As one facet of the BEST-BSIERP Bering Sea program, we determined the proximate composition and essential allometric relationships of multiple species of euphausiids collected over three years in the eastern Bering Sea. Three euphausiid species were examined: Thysanoessa inermis, Thysanoessa raschii, and Thysanoessa longipes. While the three species were similar with respect to size, T. inermis had the highest average wet and dry weights per size class, as well as highest carbon and caloric concentrations. Among the three species, T. inermis and T. longipes had similar lipid concentrations, with T. longipes showing higher average lipid concentrations. Empirical equations were developed to describe fundamental relationships between length, weight, PC/PN, and calorie and lipid content for the three species over the full range of sizes encountered in the study area. Such relationships increase our understanding of how euphausiids contribute to the carbon budget and energy input in the eastern Bering Sea system and help to define realistic parameters for ongoing and future modeling efforts.
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The role of lipids during embryonic development of the euphausiids Euphausia pacifica and Thysanoessa spinifera
Limnology and Oceanography, 2006Co-Authors: H. Rodger Harvey, Jaime Gómez-gutiérrez, William T. PetersonAbstract:To understand the role of lipids during early embryogenesis, major lipid classes together with individual fattyacid and sterol composition were determined in embryos from multiple developmental stages of the euphausiids Euphausia pacifica and Thysanoessa spinifera. Average lipid content in embryos of E. pacifica and T. spinifera from the earliest stage (multicell) were 4.45 and 3.69 mg embryo21, respectively. During development, the lipid content decreased at similar rates in the embryos of both species. In contrast to many crustacean eggs, phospholipids were the dominant lipid class in all embryonic stages, with decreasing concentrations seen during development. Individual fatty acids and sterols showed selective utilization during early developmental stages. The dominant fatty acids were 16:0 and 16:1v7 and 20:5v3, with most polyunsaturated fatty acids preferentially metabolized throughout early stages. An exception was 22:6v3, which remained near constant through all stages. Cholesterol was the dominant sterol (.82% of total sterols) in embryos, with only minor changes during development. The appearance of algal sterols and fatty alcohols, including phytol, in T. spinifera embryos suggests that considerable amounts of algal lipids are directly allocated to eggs during vitellogenesis. Despite the substantial changes in lipid amount and composition during embryo development, the presence of phospholipids as the dominate lipid store acts to moderate changes in egg-sinking rate for both species until the late (early and late limb-bud) stages of development.
Arnoldus Schytte Blix - One of the best experts on this subject based on the ideXlab platform.
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Digestibility of krill (Euphausia superba and Thysanoessa sp.) in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus)
The British journal of nutrition, 1994Co-Authors: Per-erik Mårtensson, Erling S. Nordøy, Arnoldus Schytte BlixAbstract:Apparent digestible efficiency (% DE) was studied by use of dietary Mn as an inert marker, in minke whales (Balaenoptera acutorostrata) and crabeater seals (Lobodon carcinophagus) which had been eating krill. Median % DE in minke whales (n 5) eating krill of the genus Thysanoessa sp. (energy density (ED) 23·8 kJ/g) was 93 (range 87–93). Median % DE in crabeater seals (n 6) eating krill of the species Euphausia superba (ED 20·8 kJ/g) was 84 (range 79–85), which is significantly lower than the % DE of krill in minke whales (P = 0·008). Since the chemical composition in E. superba and in Thysanoessa sp. is similar, it is suggested that the complex multi-stomached system of minke whales, which contains both chitinase (EC 3.2.1.14)-producing as well as several other types of bacteria, is superior to the single-stomached system of crabeater seals with regard to krill digestion. It is worth noting, however, that the % DE of krill in the crabeater seal is still very high.
Mette Dalgaard Agersted - One of the best experts on this subject based on the ideXlab platform.
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Thysanoessa raschii (Euphausiacea), adult morphology and map of sampling sites.
2015Co-Authors: Hasna Akther, Mette Dalgaard Agersted, Jørgen OlesenAbstract:(A) Adult morphology of Thysanoessa raschii (Euphausiacea) (photo by permission from Russel Hopcroft). (B, C) Map of Godthåbsfjord, SW Greenland, with sampling stations indicated by black dots and station numbers. The larvae examined in this study originated from station GF8 (arrow on C).
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gut evacuation rate and grazing impact of the krill Thysanoessa raschii and t inermis
Marine Biology, 2015Co-Authors: Frederik Wolff Teglhus, Mette Dalgaard Agersted, Kristine Engel Arendt, Torkel Gissel NielsenAbstract:Gut evacuation rates and ingestion rates were measured for the krill Thysanoessa raschii and T. inermis in Godthabsfjord, SW Greenland. Combined with biomass of the krill community, the grazing potential on phytoplankton along the fjord was estimated. Gut evacuation rates were 3.9 and 2.3 h−1 for T. raschii and T. inermis, respectively. Ingestion rates were 12.2 ± 7.5 µg C mg C−1 day−1 (n = 4) for T. inermis and 4.9 ± 3.2 µg C mg C−1 day−1 (n = 4) for T. raschii, corresponding to daily rations of 1.2 and 0.5 % body carbon day−1. Clearance experiments conducted in parallel to the gut evacuation experiment gave similar results for ingestion rates and daily rations. Krill biomass was highest in the central part of the fjord’s length, with T. raschii dominating. Community grazing rates from krill and copepods were comparable; however, their combined impact was low, estimated as <1 % of phytoplankton standing stock being removed per day during this late spring study.
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The functional biology and trophic role of krill ( Thysanoessa raschii ) in a Greenlandic fjord
Marine Biology, 2011Co-Authors: Mette Dalgaard Agersted, Torkel Gissel Nielsen, Peter Munk, Bent Vismann, Kristine Engel ArendtAbstract:Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the Godthabsfjord (64°N, 51°W) SW Greenland, through a combination of fieldwork and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily ration of 1% body C d−1. Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 μm, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory behaviour of krill will concentrate and elevate the grazing in specific areas of the euphotic zone.
Torkel Gissel Nielsen - One of the best experts on this subject based on the ideXlab platform.
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gut evacuation rate and grazing impact of the krill Thysanoessa raschii and t inermis
Marine Biology, 2015Co-Authors: Frederik Wolff Teglhus, Mette Dalgaard Agersted, Kristine Engel Arendt, Torkel Gissel NielsenAbstract:Gut evacuation rates and ingestion rates were measured for the krill Thysanoessa raschii and T. inermis in Godthabsfjord, SW Greenland. Combined with biomass of the krill community, the grazing potential on phytoplankton along the fjord was estimated. Gut evacuation rates were 3.9 and 2.3 h−1 for T. raschii and T. inermis, respectively. Ingestion rates were 12.2 ± 7.5 µg C mg C−1 day−1 (n = 4) for T. inermis and 4.9 ± 3.2 µg C mg C−1 day−1 (n = 4) for T. raschii, corresponding to daily rations of 1.2 and 0.5 % body carbon day−1. Clearance experiments conducted in parallel to the gut evacuation experiment gave similar results for ingestion rates and daily rations. Krill biomass was highest in the central part of the fjord’s length, with T. raschii dominating. Community grazing rates from krill and copepods were comparable; however, their combined impact was low, estimated as <1 % of phytoplankton standing stock being removed per day during this late spring study.
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The functional biology and trophic role of krill ( Thysanoessa raschii ) in a Greenlandic fjord
Marine Biology, 2011Co-Authors: Mette Dalgaard Agersted, Torkel Gissel Nielsen, Peter Munk, Bent Vismann, Kristine Engel ArendtAbstract:Despite being a key zooplankton group, knowledge on krill biology from the Arctic is inadequate. The present study examine the functional biology and evaluate the trophic role of krill in the Godthabsfjord (64°N, 51°W) SW Greenland, through a combination of fieldwork and laboratory experiments. Krill biomass was highest in the middle fjord and inner fjord, whereas no krill was found offshore. The dominating species Thysanoessa raschii revealed a type III functional response when fed with the diatom Thalassiosira weissflogii. At food saturation, T. raschii exhibited a daily ration of 1% body C d−1. Furthermore, T. raschii was capable of exploiting plankton cells from 5 to 400 μm, covering several trophic levels of the pelagic food web. The calculated grazing impact by T. raschii on the fjord plankton community was negligible. However, the schooling and migratory behaviour of krill will concentrate and elevate the grazing in specific areas of the euphotic zone.
