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| 2. |
- Arendt, Kristine Engel, et al.
(författare)
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Differences in plankton community structure along the Godthåbsfjord, from the Greenland Ice sheet to offshore waters
- 2010
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Ingår i: Marine Ecology Progress Series. - 0171-8630. ; 401, s. 49-62
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Tidskriftsartikel (refereegranskat)abstract
- This study describes differences in plankton community structure and in chemical and physical gradients between the offshore West Greenland Current system and inland regions close to the Greenland Ice Sheet during the post-bloom in Godthåbsfjorden (64° N, 51° W). The offshore region had pronounced vertical mixing, with centric diatoms and Phaeocystis spp. dominating the phytoplankton, chlorophyll (chl) a (0.3 to 3.9 μg l–1) was evenly distributed and nutrients were depleted in the upper 50 m. Ciliates and heterotrophic dinoflagellates constituted equal parts of the protozooplankton biomass. Copepod biomass was dominated by Calanus spp. Primary production, copepod production and the vertical flux were high offshore. The water column was stratified in the fjord, causing chl a to be concentrated in a thin sub-surface layer. Nutrients were depleted above the pycnocline, and Thalassiosira spp. dominated the phytoplankton assemblage close to the ice sheet. Dinoflagellates dominated the protozooplankton biomass, whereas copepod biomass was low and was dominated by Pseudocalanus spp. and Metridia longa. Primary production was low in the outer part of the fjord but considerably higher in the inner parts of the fjord. Copepod production was exceeded by protozooplankton production in the fjord. The results of both physical/chemical factors and biological parameters suggest separation of offshore and fjord systems.
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| 3. |
- Haraldsson, Matilda, 1980, et al.
(författare)
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The relationship between fish and jellyfish as a function of eutrophication and water clarity
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 471, s. 73-85
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Tidskriftsartikel (refereegranskat)abstract
- There is a concern that blooms of cnidarians and ctenophores, often referred to as jellyfish, are increasing in frequency and intensity worldwide and that there is a shift from fish- to jellyfish-dominated systems. We present an idealized analysis of the competitive relationship between zooplanktivorous jellyfish that is based on a generic model, termed ‘Killing the Winner’ (KtW), for the coexistence of 2 groups utilizing the same resource. Tactile predation by jellyfish makes them less dependent on water optics than fish using vision, and we modified the KtW model to account for this particular trait difference. Expectations of the model are illustrated by use of observations from the Baltic Sea. The model predicts a general succession on how mass of the system distributes when going from an oligotrophic to a eutrophic system. Initially the mass of the system accumulates at the level of the common resource (zooplankton) and planktivorous fish (sprat/herring). At one point, with increased eutrophication, mass starts to accumulate at the level of the top predator (cod) and at a later point, at the level of the jellyfish. For those organisms utilizing vision (fishes) an optimal degree of eutrophication and water clarity is predicted due to a 2-sided effect of eutrophication.
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| 4. |
- Maar, M., et al.
(författare)
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Trophodynamic function of copepods, appendicularians and protozooplankton in the late summer zooplankton community in the Skagerrak
- 2004
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 144:5, s. 917-933
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Tidskriftsartikel (refereegranskat)abstract
- The study was carried out in the Skagerrak during late summer when population development in the pelagic cycle culminated in the yearly maximum in zooplankton biomass. The cyclonic circulation of surface water masses created the characteristic dome-shaped pycnocline across the Skagerrak. The large dinoflagellate Ceratium furca dominated the phytoplankton biomass. Ciliates and heterotrophic dinoflagellates were the major grazers and, potentially, consumed 43-166% of daily primary production. The grazing impact of copepods was estimated from specific egg production rates and grazing experiments. The degree of herbivory differed between species (14-85%), but coprophagy (e.g. feeding on fecal pellets) and ingestion of microzooplankton were also important. The appendicularian Oikopleura dioica was present in lower numbers than copepods, but cleared a large volume of water. The grazing impact of copepods and O. dioica was estimated to 57+/-24% and 12+/-12% of daily primary production, respectively. Sedimentation of organic material (30 m) varied between 169 and 708 mg C m(-2) day(-1), and the contribution from the mesozooplankton (copepod fecal pellets and mucus houses with attached phytodetritus of O. dioica) was 5-33% of this sedimentation. Recycling of fecal pellets and mucus houses in the euphotic zone was 59% and 36%, respectively. However, there was a high respiration of organic material by microorganisms in the mid-water column, and 34% of the sedimenting material actually reached the benthic community in the deep, central part of the Skagerrak.
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| 5. |
- Morf, Andrea, 1968, et al.
(författare)
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Remissyttrande: Sveriges nationella havsplaner 2018
- 2018
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Havsmiljöinstitutet lämnar härmed synpunkter på dokumenten Förslag till Havsplan, Miljökonsekvensbeskrivning (MKB) samt Hållbarhetsbedömning (HB) för havsplanområdena Bottenviken, Östersjön och Västerhavet, utarbetade av Havs- och Vattenmyndigheten (HaV). Havsmiljöinstitutets (och ingående universitets) experter har tolkat sin uppgift bredare än att svara på remissfrågorna om planernas innehåll och kunskapsbas. Institutet kommenterar ur ett brett tvärvetenskapligt perspektiv följande: 1. rollen som akademin och institutet har spelat i havsplaneringen hittills, 2. kust- och havsplanerings¬systemet och processen, samt 3. dokumenten och kunskapsbasen. Här ingår förslag hur allt kunde utvecklas vidare, inklusive Institutets egen roll som länk mellan forskning och förvaltning, både på kortare och längre sikt.
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| 6. |
- Møller, Eva Friis, et al.
(författare)
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The effect of changes in temperature and food on the development of calanus finmarchicus and Calanus helgolandicus populations
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590. ; 57, s. 211-220
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Tidskriftsartikel (refereegranskat)abstract
- We studied the response in development times of Calanus finmarchicus and Calanus helgolandicus to changes in temperature and food conditions. Grazing experiments were performed at different temperatures for both species, and the results were implemented in a stage-resolved zooplankton population model that predicted development times from biomass increments controlled by ingestion and metabolic losses. Predictions were validated against development data from the literature, and show that C. finmarchicus develops faster than C. helgolandicus below 11 °C and slower above. The different relative development rates of the species are related to different temperature responses in ingestion rates. A temperature increase of 1 °C to 2 °C may have consequences for the relative contribution of C. helgolandicus and C. finmarchicus to the copepod community, and both seasonal and spatial displacements of the Calanus populations can be expected under climate change.
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| 10. |
- Tönnesson, Kajsa, 1971, et al.
(författare)
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Diet of the chaetognaths Sagitta setosa and S-elegans in relation to prey abundance and vertical distribution
- 2005
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 289, s. 177-190
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Tidskriftsartikel (refereegranskat)abstract
- The chaetognaths Sagitta setosa and S. elegans and their potential prey organisms were collected from 6 different depth strata on 6 day and night occasions in the Gullmar fjord, west Sweden. The chaetognaths were analysed for gut contents and predation impact estimated. Number of prey per chaetognath (NPC) ranged from 0.2 to 1.0 for S. setosa and 0.4 to 0.9 for S. elegans, with significantly higher values at night. For S. setosa, small copepods dominated gut contents, with the addition of the appendicularian Oikopleura dioica and chaetognaths later in the season. For S. elegans, the great majority of prey were Calanus copepodites. Predation impact was strong on single copepod species, increasing from 0.4 to a maximum of 48 % of the individuals removed daily by S. setosa at the end of October. S. elegans consumed 5 to 18 % of the deeper dwelling Calan us community daily. Cannibalism was pronounced in S. setosa; in October, 74 to 84 % of the population could potentially be removed each day, Selective feeding was observed in S. setosa by estimating clearance rates for different prey. Pseudocalanus sp. was over-represented in the guts (clearance 120 ml ind.(-1) d(-1)) as well as S, setosa (124 ml ind.(-1) d(-1)) and Paracalanus parvus (40 ml ind.(-1) d(-1)). S. setosa was able to maintain a daily ration of 11 to 17 % of body weight despite a rapid decline in copepod prey abundance, and this was possible through cannibalism and intense predation on O. dioica.
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| 11. |
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| 12. |
- Tönnesson, Kajsa, 1971, et al.
(författare)
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Feeding and production of the carnivorous copepod Pareuchaeta norvegica in the Skagerrak
- 2006
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 314, s. 213-225
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Tidskriftsartikel (refereegranskat)abstract
- The vertical and horizontal distribution of the carnivorous copepod Pareuchaeta norvegica Boeck and its potential prey were analysed in the Skagerrak during spring 1999 and autumn 2000. Feeding by P. norvegica was assessed by measuring egestion of faecal pellets. Pellet production at night was significantly higher than during the day. Feeding rates for females ranged from 1.4 to 5.2 prey d(-1) in the spring and from 6.2 to 8.6 prey d(-1) in the autumn. Feeding rates for juveniles were higher in both seasons. Peak spermatophore attachment and fertilisation occurred during spring when the proportion of males was also highest. The weight-specific egg production rate was estimated by the egg ratio method and ranged from 0.31 to 0.73% d(-1) in the spring and from 0.42 and 0.66% d(-1) in the autumn; no significant difference between seasons was found. The number and the total volume of the eggs were positively correlated to prosome length of the females. The population of F norvegica ingested 2.0 to 4.6% of the spring copepod population daily and 2.4 to 6.5% of the autumn population. The predation impact of F norvegica was equivalent to 6 to 14 and 9 to 16% of the copepod population production in spring and autumn, respectively, illustrating the importance of this species in the Skagerrak pelagic ecosystem. Compared with the other important invertebrate predators, the chaetognaths, the impact of R norvegica was 10 to 100 times higher in both seasons.
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| 16. |
- Tönnesson, Kajsa, 1971, et al.
(författare)
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Grazing impact of Oikopleura dioica and copepods on an autumn plankton community
- 2005
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Ingår i: Marine Biology Research. - : Informa UK Limited. - 1745-1000 .- 1745-1019. ; 1:5, s. 365-373
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Tidskriftsartikel (refereegranskat)abstract
- Copepods and appendicularians are major grazers in the pelagic environment. They have different retention efficiencies for prey and may therefore exert a variable grazing pressure on the spectrum of pico- to micro-plankton. We determined clearance rates of both groups at one station during 24 h in the Gullmar fjord, west Sweden, in autumn 1999. Total potential prey biomass ranged from 75 mu g C l(-1) at the surface to 14 mu g C l(-1) at 30 m with a dominance of larger dinoflagellates (10-25 mu m athecate species and Gymnodinium /Gyrodinium sp.) and the pennate diatom Pseudo -nitzschia sp. Grazer biomass was dominated by copepods (Acartia clausi, Paracalanus parvus) and appendicularians (Oikopleura dioica). O. dioica showed non-selective clearance rates of 0.7-1.8 ml mu g C-1 h(-1) on most diatoms, flagellates and ciliates, whereas Pseudo -nitzschia sp. and dinoflagellates and ciliates > 25 mu m were not removed by O. dioica. Appendicularian grazing impact was 0.06% d(-1) on the phytoplankton and 0.4% d(-1) on bacterial biomass. Despite a seven-fold higher biomass, the grazing impact of copepods on phytoplankton biomass was only 0.28% d(-1) indicating that O. dioica had a proportionally greater impact and, in contrast to copepods, also utilised bacteria. The low observed grazing impact was due to a low grazer biomass and a prey community largely unavailable to the investigated grazers.
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