| 1. |
- Dahlgren, Kristin, 1979-, et al.
(författare)
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Planktonic production and carbon transfer efficiency along a north-south gradient in the Baltic sea
- 2010
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Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 409, s. 77-94
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Tidskriftsartikel (refereegranskat)abstract
- A 1 yr study was conducted along a brackish-water production gradient to enhance the understanding of factors governing pelagic food web function. This was achieved by measuring carbon transfer efficiency (TE) from the basal resource to an intermediate trophic level. TE was defined as mesozooplankton carbon consumption rate divided by production at the basal trophic level, which is composed of phytoplankton and bacteria. A north–south transect in the Baltic Sea was used as a model system, with 2 stations each in the Bothnian Bay, Bothnian Sea and Baltic Proper being sampled 5 to 8× during 2006. In addition, data from monitoring programmes were used, which comprised 10 to 22 samplings stn–1. TE was expected to be governed by the size distribution of phytoplankton and due to the nutrient gradient, we expected to find an optimal cell size, and thus also a high TE, in the intermediate-productive Bothnian Sea. The basal production during summer/autumn increased 5-fold from north to south, while the mesozooplankton carbon consumption rate exhibited a peak inthe Bothnian Sea, being ~3× higher than in both Bothnian Bay and Baltic Proper. TE was found to be intermediate in the Bothnian Bay (average: 0.8), highest in the Bothnian Sea (1.6), and lowest in the Baltic Proper (0.2). We suggest that the variation in carbon transfer efficiency can be explained by the composition of the phytoplankton community, the abundance balance between copepods and cladocerans, as well as the species composition of mesozooplankton in relation to the size structure of phytoplankton.
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| 2. |
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| 3. |
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| 4. |
- Berglund, Johnny, et al.
(författare)
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Efficiency of a phytoplankton-based and a bacterial-based food web in a pelagic marine system
- 2007
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Ingår i: Limnology and Oceanography. ; 52:1, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- he food web efficiency in two contrasting food webs, one phytoplankton based and one bacteria based, was studied in a mesocosm experiment using seawater from the northern Baltic Sea. Organisms included in the experiment were bacteria, phytoplankton, protozoa, and mesozooplankton (copepods). A phytoplankton-based food web was generated by incubating at a high light level with the addition of nitrogen and phosphorus (NP). A bacteria-based food web was created by adding carbon, nitrogen, and phosphorus (CNP) and incubating at a lower light level. In the CNP treatment bacteria dominated the productivity (91%), while in the NP treatment phytoplankton were dominant producers (74%). The phytoplankton community in the NP treatment was dominated by autotrophic nanoflagellates. The food web efficiency, defined as mesozooplankton productivity per basal productivity (phytoplankton + bacteria), was 22% in the phytoplankton-based food web and 2% in the bacteria-based food web. This discrepancy could be explained by 1�xtra trophic levels in the bacteria-based food web where carbon passed through flagellates and ciliates before reaching mesozooplankton, while in the phytoplankton-based food web there was a direct pathway from phytoplankton to mesozooplankton. The results were supported by stable isotope analysis of mesozooplankton. We propose that climate change, with increased precipitation and river runoff in the Baltic Sea, might favor a bacteria-based food web and thereby reduce pelagic productivity at higher trophic levels.
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| 5. |
- Buhl-Mortensen, Lene, et al.
(författare)
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The inland deep sea : benthic biotopes in the Sognefjord
- 2020
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Ingår i: Seafloor geomorphology as benthic habitat. - : Elsevier. - 9780128149607 - 9780128149614 ; , s. 355-372
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Bokkapitel (refereegranskat)abstract
- The Sognefjord is a geologically unique, long, and deep glacial valley, stretching more than 200km inland with a maximum depth of 1300m. Surprisingly little is known about the seafloor environment and bottom communities of this, in a global perspective, spectacularly long and deep fjord. Megafaunal species richness, seabed substrates, and biotopes of the fjord were studied in 2000, 2001, 2014, and 2015 using underwater video as part of a joint project between the University of Bergen and the Institute of Marine Research with funds from the Norwegian Biodiversity Information Centre. Clear gradients in species richness and composition were found related to distance into the fjord, depth, and landscape features (fjord sides, basin plain, shallower side fjords). Detrended Correspondence Analyses of results from detailed video annotations indicated the presence of six biotopes with characteristic species composition and environment. Earlier fjord studies have shown that deep-sea species often occur shallower in fjord basins than in adjacent offshore areas. Furthermore, the isolation of fjord basins behind one or more sills can lead to mass occurrence of species that by chance have been introduced and been able to establish dense populations. The limited contact between fjord basins in relation to the open ocean and between side fjords makes the extremely large and branched Sognefjord particularly interesting for studies of the effects of connectivity on bottom communities. Similarities to communities outside the fjord are discussed.
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| 6. |
- Båmstedt, Ulf, et al.
(författare)
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A cost-precision model for marine environmental monitoring, based on time-integrated averages
- 2017
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Ingår i: Environmental Monitoring & Assessment. - : Springer. - 0167-6369 .- 1573-2959. ; 189:7
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Tidskriftsartikel (refereegranskat)abstract
- Ongoing marine monitoring programs are seldom designed to detect changes in the environment between different years, mainly due to the high number of samples required for a sufficient statistical precision. We here show that pooling over time (time integration) of seasonal measurements provides an efficient method of reducing variability, thereby improving the precision and power in detecting inter-annual differences. Such data from weekly environmental sensor profiles at 21 stations in the northern Bothnian Sea was used in a cost-precision spatio-temporal allocation model. Time-integrated averages for six different variables over 6 months from a rather heterogeneous area showed low variability between stations (coefficient of variation, CV, range of 0.6-12.4%) compared to variability between stations in a single day (CV range 2.4-88.6%), or variability over time for a single station (CV range 0.4-110.7%). Reduced sampling frequency from weekly to approximately monthly sampling did not change the results markedly, whereas lower frequency differed more from results with weekly sampling. With monthly sampling, high precision and power of estimates could therefore be achieved with a low number of stations. With input of cost factors like ship time, labor, and analyses, the model can predict the cost for a given required precision in the time-integrated average of each variable by optimizing sampling allocation. A following power analysis can provide information on minimum sample size to detect differences between years with a required power. Alternatively, the model can predict the precision of annual means for the included variables when the program has a pre-defined budget. Use of time-integrated results from sampling stations with different areal coverage and environmental heterogeneity can thus be an efficient strategy to detect environmental differences between single years, as well as a long-term temporal trend. Use of the presented allocation model will then help to minimize the cost and effort of a monitoring program.
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| 7. |
- Båmstedt, Ulf, et al.
(författare)
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An indoor pelagic mesocosm facility to simulate multiple water-column characteristics
- 2018
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Ingår i: International Aquatic Research. - : Springer. - 2008-4935 .- 2008-6970. ; 10:1, s. 13-29
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Tidskriftsartikel (refereegranskat)abstract
- Mesocosms are important research tools in aquatic ecology because they close the gap between laboratory studies at the individual or lower organization level and field studies at the population and ecosystem level. However, most mesocosm studies regarding the pelagic environment do not consider the effects of physical factors like water-column stratification, turbulence and mixing. Neglecting such factors might bias the results compared to the natural system. Using a unique indoor mesocosm facility, we present results on how different water-column stratifications can be made and how they act as barriers for exchange between water layers. Turbulent mixing, simulated by vertically rotating incubation vessels, is shown to be of high importance for primary production, generating up to nine times higher production in humus-rich water than incubation vessels at fixed depths. Convective stirring is shown to be an attractive method for generating different turbulence conditions, and different temperature settings can be used to get turnover times from 84 h or more down to 17 min for a 5-m water parcel. We also demonstrate how an anoxic bottom layer can be achieved by stimulating heterotrophic bacteria through addition of bioavailable organic carbon.
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| 8. |
- Båmstedt, Ulf
(författare)
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Comparing static and dynamic incubations in primary production measurements under different euphotic and mixing depths
- 2019
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 827:1, s. 155-169
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Tidskriftsartikel (refereegranskat)abstract
- Since phytoplankton production is usually estimated from static incubations (fixed depths or light levels), a mesocosm study was performed to evaluate the significance of mixing depth, mixing intensity and load of humus of natural phytoplankton assemblages. Vertically rotated (dynamic) incubations usually gave higher results than static incubations in humus-rich water. Mixing intensity was of significant importance in one of 2years tested, but strong interaction effects with humus complicated the explanation. Differences in primary production between dynamic incubations did not fully reflect the received PAR dose, and increased humus and increased mixing depth increased the photo-assimilation efficiency. Different single-depth incubations did not provide a shortcut method to measure water-column primary production with high accuracy. Results diverged from theoretical estimates based on recent combined photo-biological and physical environmental models. The large variability in responses to mixing is supposed to reflect species-specific adaptations and pre-history regarding quantity (photons) and quality (spectral distribution) of the optical environment in an assemblage of different species. The proportional abundance of each species with its specific characters will therefore strongly influence bulk primary production. Due to such variable responses, clear guidelines for a best practice in primary production measurements cannot be given, based on the present results.
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| 9. |
- Båmstedt, Ulf
(författare)
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Decomposing medusae as substrata for bacterial growth and their potential contribution to environmental hypoxia
- 2022
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Ingår i: Estuarine, Coastal and Shelf Science. - : Academic Press. - 0272-7714 .- 1096-0015. ; 276
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Tidskriftsartikel (refereegranskat)abstract
- Decomposing jellyfishes at 9ᵒC showed exponential loss in wet and dry weight, particulate (POC) and dissolved (DOC) organic carbon and particulate organic nitrogen (PON), with turnover times of 3.5–4.2 d. The amount (%) carbon and nitrogen of carcasses, decreased linearly over time, but the C/N atomic ratio remained stable at 7. The daily decline of POC and PON, as a % of starting C and N, both showed a negative relationship with medusa weight, but with a stable POC/PON atomic ratio at 9.1. Five morphological groups of bacteria that co-occurred with the medusa, all exhibited exponential growth, with an average daily biomass doubling rate between 2.8 and 4.9. Over a 3-d period the biomass ratio between coccoids and spirills increased by a factor of 76. Oxygen consumption in the surrounding water was on average 0.34 ± 0.10 mg l−1 h−1 and slightly increasing over time. Assuming the oxygen consumption being a function of bacterial respiration, the bacterial growth efficiency increased exponentially from <3% during the first 25 h to 16% after 55 h. Incorporating all of these results, the potential impact of decomposing jellyfishes on environmental oxygen concentration could be simulated, with the biomass of decomposing medusae and water-mixing volume as input variables. Such simulations would be useful to forecast environmental hypoxia.
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| 10. |
- Båmstedt, Ulf, et al.
(författare)
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Ecology and behavior of Bolinopsis infundibulum (Ctenophora; Lobata) in the Northeast Atlantic
- 2015
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 759:1, s. 3-14
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Tidskriftsartikel (refereegranskat)abstract
- Results from field surveys with net sampling and video profiling, combined with laboratory experiments on feeding and growth, revealed the ecological function of Bolinopsis infundibulum in northern temperate coastal waters. B. infundibulum reaching a peak abundance of around 250 ctenophores m(-2), in mid-May, followed by a dramatic reduction over the next few weeks, presumably explained by predation from the ctenophore Beroe cucumis. The field data on maximum individual body height in the population indicated an instantaneous growth rate of 0.129 d(-1). Newly hatched cydippid larvae showed an average instantaneous growth rate of 0.240 d(-1) over 4 weeks, whereas ctenophores in the size range of 4.4-9.8 mm height gave instantaneous growth rates between 0.10 and 0.20 d(-1). B. infundibulum disappeared from surface water in mid-June, but big individuals were found in deeper water, where they preyed on copepods. The results indicate that the new generation of the year was recruited from February onwards. Laboratory predation and digestion experiments showed a continuous increase in predation rate with increased prey abundance, throughout the tested range of 5-400 copepods l(-1), and a digestion time increasing from 39 min with a single copepod ingested to 73 min with 8 copepods ingested.
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| 11. |
- Båmstedt, Ulf, et al.
(författare)
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Fecundity and early life of the deep-water jellyfish Periphylla periphylla
- 2020
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Ingår i: Journal of Plankton Research. - : OXFORD UNIV PRESS. - 0142-7873 .- 1464-3774. ; 42:1, s. 87-101
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Tidskriftsartikel (refereegranskat)abstract
- Comparisons over 6 years of three Norwegian fjord populations of the deep-water scyphomedusa Periphylla periphylla are presented. A minor part of the population in Lurefjord is migrating to the surface during night, which benefits mating encounters by increasing abundance per unit volume and decreasing the distance between individuals. Simulations using a typical water-column density profile and Stoke's law show that fertilized eggs released in the surface quickly reach a depth where light is insufficient for visual predators. Consequently, the distribution of the smallest juveniles was strongly skewed towards higher depths in all three fjords studied. Mature females in Sognefjord were 4-5 times less abundant than in Lurefjord and Halsafjord, but due to a larger size and strong exponential relationship between size and number of mature oocytes, the potential recruitment rate as recruits m(-2) year(-1) was not much different from the other two fjords. Nevertheless, the observed number of small (<1 cm) juveniles was 18-31 times higher in Sognefjord than in the other two fjords, and it is assumed that the deeper habitat (up to 1300 m) compared to the other fjords (up to 440 and 530 m) is a superior habitat for the early development of P. periphylla.
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| 12. |
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| 13. |
- Båmstedt, Ulf
(författare)
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Life history traits of the deep-water medusa Periphylla periphylla as revealed through failure and recovery of recruitment
- 2023
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Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier. - 0272-7714 .- 1096-0015. ; 282
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Tidskriftsartikel (refereegranskat)abstract
- Extended recruitment failure and subsequent success of the coronate medusa Periphylla periphylla in a Norwegian fjord provided a unique opportunity to estimate age-related biological traits by combining individual size distribution in the population over time with previously published data. The average growth rate decreased exponentially with age, from 0.55% day−1 during the first year to <0.17% day−1 after four years. This species becomes mature at the third year, when females carry approximately 10 mature oocytes. At an age of 9 years, the medusa is on average 12 cm in diameter and carries over 1000 mature oocytes. Recruitment of juveniles, 0.5–1 cm diameter, was estimated to be 15 female−1 year−1 in Halsafjord; mortality from egg to juvenile 1 cm in diameter, using oocyte turnover times (T) of 1–12 months, was 93% (T = 12 months) to 99.95% (T = 1 month). Eggs and juveniles younger than 10 months are not capable of vertical migration and remain deeper than the sill depth where regular fjord circulation occurs. Therefore they are only vulnerable to deep-water renewal, and a fjord population of P. periphylla is estimated to gradually decrease recruitment with increased frequency of deep-water renewal and reach zero recruitment with renewal intervals of 10 months or less. It is hypothesized that differences in regular and intermittent deep-water renewal is the main factor causing variability in size (age) distribution between fjord populations.
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| 14. |
- Båmstedt, Ulf, 1946-, et al.
(författare)
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Mixing depth and allochthonous dissolved organic carbon: controlling factors of coastal trophic balance
- 2016
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Ingår i: Marine Ecology Progress Series. - Oldendorf/Luhe : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 561, s. 17-29
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: The interacting effects of different mixing depths and increased allochthonous dissolved organic carbon (DOC) on the ratio of heterotrophic to autotrophic production (i.e. trophic balance) was evaluated in a mesocosm study with a stratified water column. An autumn plankton community from the northern Bothnian Sea showed significantly decreased phytoplankton production and somewhat increased bacterial production with added DOC. In addition, increased mixing depth further reduced phytoplankton production. With a deep pycnocline and added DOC, the system became net-heterotrophic, with an average bacteria-to-phytoplankton production ratio of 1.24. With a deep pycnocline without added DOC, the trophic balance was changed to 0.44 (i.e. autotrophic). With a shallow pycnocline, the system remained net-autotrophic irrespective of DOC addition. We propose that increased precipitation in northern Europe due to climate change may result in changed density stratification and increased allochthonous DOC transport to the sea, leading to more heterotrophic coastal aquatic ecosystems. Such a scenario may entail reduced biological production at higher trophic levels and enhanced CO2 emission to the atmosphere.
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| 15. |
- Båmstedt, Ulf
(författare)
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Productivity related to ambient photon flux for phytoplankton communities under different turbid conditions
- 2019
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117. ; 837:1, s. 109-115
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton productivity standardized to chlorophyll a and photon flux (mg C mg chl. a(-1) mol photons(-1)) of natural communities from northern Bothnian Sea under dynamic (vertically rotating) incubations and different optical conditions was studied during four mesocosm experiments between April 2013 and April 2016. The standardized productivity showed a positive exponential relationship with calculated optical depth (P<0.001 in all four cases) although a considerably weaker one for one of the series where the community was pre-adapted to the same optical condition as used in the measurements. This series also showed a lower regression slope than the three non-adapted series, which in turn showed identical regression slopes, thus indicating a similar response on the standardized productivity to short-term changes in average ambient photon flux and mixing depth. These results indicate that phytoplankton communities in environments with episodic inflow and mixing of humus-rich water can partly compensate for the reduced photon flux by increased production efficiency.
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| 16. |
- Calbet, Albert, et al.
(författare)
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Future Climate Scenarios for a Coastal Productive Planktonic Food Web Resulting in Microplankton Phenology Changes and Decreased Trophic Transfer Efficiency
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:4, s. e94388-
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Tidskriftsartikel (refereegranskat)abstract
- We studied the effects of future climate change scenarios on plankton communities of a Norwegian fjord using a mesocosm approach. After the spring bloom, natural plankton were enclosed and treated in duplicates with inorganic nutrients elevated to pre-bloom conditions (N, P, Si; eutrophication), lowering of 0.4 pH units (acidification), and rising 3 degrees C temperature (warming). All nutrient-amended treatments resulted in phytoplankton blooms dominated by chain-forming diatoms, and reached 13-16 mu g chlorophyll (chl) a l(-1). In the control mesocosms, chl a remained below 1 mu g l(-1). Acidification and warming had contrasting effects on the phenology and bloom-dynamics of autotrophic and heterotrophic microplankton. Bacillariophyceae, prymnesiophyceae, cryptophyta, and Protoperidinium spp. peaked earlier at higher temperature and lower pH. Chlorophyta showed lower peak abundances with acidification, but higher peak abundances with increased temperature. The peak magnitude of autotrophic dinophyceae and ciliates was, on the other hand, lowered with combined warming and acidification. Over time, the plankton communities shifted from autotrophic phytoplankton blooms to a more heterotrophic system in all mesocosms, especially in the control unaltered mesocosms. The development of mass balance and proportion of heterotrophic/autotrophic biomass predict a shift towards a more autotrophic community and less-efficient food web transfer when temperature, nutrients and acidification are combined in a future climate-change scenario. We suggest that this result may be related to a lower food quality for microzooplankton under acidification and warming scenarios and to an increase of catabolic processes compared to anabolic ones at higher temperatures.
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| 17. |
- Dahlgren, Kristin, 1979-
(författare)
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Food web structures and carbon transfer efficiencies in a brackish water ecosystem
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two differently structured food webs can be distinguished in the pelagic habitat of aquatic systems; the classical one (autotrophic) with phytoplankton as a base and the microbial food web (heterotrophic) with bacteria as a base. Energy (produced at the basal trophic level) reaches higher trophic levels, i.e. zooplankton, directly in the classical food web in contrast to the microbial food web where it passes through additional trophic levels before reaching zooplankton. Energy is lost between each trophic level and therefore less energy should reach higher trophic levels in the microbial food web than in the classical food web. However, factors such as edibility of prey, temperature and properties of the predator, might also influence the food web structures and functions.In this thesis I studied which factors are important for an efficient carbon transfer and how a potential climate change might alter the food web efficiency in pelagic and pelagic-benthic food webs in the Baltic Sea. Furthermore, one of the most dominant zooplankton in the northern Baltic Sea, Limnocalanus macrurus, was studied in order to establish the seasonal pattern of lipid reserves in relation to food consumption.My studies showed that the carbon transfer efficiency during summer was not directly connected to the basal production, but factors such as the ratio between heterotrophs and autotrophs, the relationship between cladocerans and calanoid copepods and the size and community structure of both phytoplankton and zooplankton were important for the carbon transfer efficiency. In a climate change perspective, the temperature as well as the relative importance of the microbial food web is likely to increase. A temperature increase may have a positive effect on the pelagic food web efficiency, whereas increasing heterotrophy will have a negative effect on the pelagic and pelagic-benthic food web efficiency, reduce the fatty acid content of zooplankton and reduce the individual weight of both zooplankton and the benthic amphipod Monoporeia affinis. During the seasonal study on the calanoid copepod L. macrurus, I found that this species is mainly a carnivore, feeding on mesozooplankton during most of the year but switches to feeding on phytoplankton when these are abundant. Furthermore, when food is scarce, it utilizes lipids that are built up during the course of the year.From these studies I can draw some major conclusions; there are many factors that influence how efficient carbon is transferred in the food web and different factors are probably of various importance in different areas. In order to determine the carbon transfer efficiency, the various strategies exerted by different organism groups have to be considered, as for example that some zooplankton utilize lipid reserves instead of feeding all year around. Also, in a climate change perspective, the pelagic-benthic food web efficiency will decrease, as will the quality of zooplankton and M. affinis, possibly having implications for higher trophic levels such as fish.
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| 18. |
- Dahlgren, Kristin, et al.
(författare)
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Seasonal variation in wax ester concentration and gut content in a Baltic Sea copepod [Limnocalanus macrurus (Sars 1863)]
- 2012
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Ingår i: Journal of Plankton Research. - Oxford : Oxford University Press. - 0142-7873 .- 1464-3774. ; 34:4, s. 286-297
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Tidskriftsartikel (refereegranskat)abstract
- Limnocalanus macrurus from Bothnian Bay in the northern part of the Baltic Sea was studied during the ice-free period (AprilDecember) in order to understand its life history and feeding biology. Our data on the population dynamics indicated that reproduction occurred during the ice-covered period, during which lipid storage was reduced to a minimum. From spring to late summer, the lipid reserve increased by a factor of 3, while the gonads of adult females were immature during this period, continuing to December as indicated by the small size of the eggs. Average stomach fullness was always ca. 50 indicating continuous feeding activity. A newly developed denaturing high-performance liquid chromatography method was used to analyse the gut contents over the study period. More than 30 taxa (at different taxonomic levels) could be identified. However, phytoplankton was only represented by one taxon (Diatomophycea), and was restricted to July. Thus, adult L. macrurus seems to have a strongly carnivorous feeding preference in the northern Baltic Sea.
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| 19. |
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| 20. |
- Degerman, Rickard, et al.
(författare)
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Food web interactions determine energy transfer efficiency and top consumer responses to inputs of dissolved organic carbon
- 2018
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 805:1, s. 131-146
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Tidskriftsartikel (refereegranskat)abstract
- Climate change projections indicate increased precipitation in northern Europe, leading to increased inflow of allochthonous organic matter to aquatic systems. The food web responses are poorly known, and may differ depending on the trophic structure. We performed an experimental mesocosm study where effects of labile dissolved organic carbon (DOC) on two different pelagic food webs were investigated, one having zooplankton as highest trophic level and the other with planktivorous fish as top consumer. In both food webs, DOC caused higher bacterial production and lower food web efficiency, i.e., energy transfer efficiency from the base to the top of the food web. However, the top-level response to DOC addition differed in the zooplankton and the fish systems. The zooplankton production increased due to efficient channeling of energy via both the bacteria land the phytoplankton pathway, while the fish production decreased due to channeling of energy mainly via the longer and less efficient bacterial pathway. We conclude that the added DOC either acted as a subsidy by increasing the production of the top trophic level (mesozooplankton), or as a sink causing decreased top consumer production (planktivorous fish).
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| 21. |
- Dinasquet, Julie, et al.
(författare)
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Cascading effects of the ctenophore Mnemiopsis leidyi on the planktonic food web in a nutrient-limited estuarine system
- 2012
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Ingår i: Marine Ecology Progress Serie. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 460, s. 49-61
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Tidskriftsartikel (refereegranskat)abstract
- Increasing biomasses of gelatinous zooplankton presumably have major implications for the structure and function of marine food webs at large; however, current data on lower trophic levels are scarce, as most studies have focused on the immediate effects on zooplankton and fish larvae only. We examined the short-term impact of larvae and adults of the invasive ctenophore Mnemiopsis leidyi on a summer planktonic food web in the estuarine southern Baltic Sea, with special emphasis on the microbial loop. Grazing by M. leidyi reduced the mesozooplankton biomass, followed by increased dinoflagellate biomass in treatments with M. leidyi. While chlorophyll a increased most in the treatments with M. leidyi, small phytoplankton and ciliates decreased in all treatments. M. leidyi had a slight effect on bacterial abundance, but not on bacterial production, ectoenzymatic activities, or community composition. Undetectable levels of phosphate and a gradual accumulation of dissolved organic carbon during the experiment suggested a malfunctioning microbial loop scenario. The experiment shows that direct and indirect short-term effects of M. leidyi on the estuarine food web are limited to higher trophic levels and indicates that top-down and bottom-up consequences of M. leidyi expansions on the microbial loop will likely depend on local nutrient conditions.
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| 22. |
- Grubisic, Lorena M., et al.
(författare)
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Effects of stratification depth and dissolved organic matter on brackish bacterioplankton communities
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 453, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- Bacterioplankton growth is often directly or indirectly controlled by external energy subsidies via organic matter inputs or solar radiation. We carried out a mesocosm experiment to assess how bacterioplankton communities responded to elevated levels of dissolved organic matter (DOM) and experimentally controlled stratification depth. The month-long experiment consisted of 2500 l mesocosms subjected to 4 experimental manipulations in triplicate: the stratification depth was set to either 1.5 or 3.5 m, with or without experimental addition of ambient levels of chromophoric DOM. DOM addition had a significant effect on bacterial community composition as assessed by terminal restriction fragment length polymorphism of amplified 16S rRNA genes. In contrast, there were no effects of the DOM amendment on bacterial biomass or production. Mixing depth and the coupled effective light climate in the photic zone also had a significant effect on bacterial community composition. Furthermore, shallow mixing depth was associated with enhanced primary production, whereas DOM addition had a negative effect on phyto plankton biomass and productivity. Our results suggest that bacterial community composition is coupled to primary production under the studied coastal nutrient regime, and point to a key role of DOM quality in controlling bacterioplankton communities.
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| 23. |
- Haraldsson, Matilda, 1980, et al.
(författare)
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Evidence of diel vertical migration in Mnemiopsis leidyi
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to describe the fine scale vertical distribution of Mnemiopsis leidyi in the Kattegat and Baltic Proper. Potential diel vertical migration was also investigated by frequent filming during a 24-hour cycle at two contrasting locations with respect to salinity stratification. The video profiles revealed a pronounced diel vertical migration at one of the locations. However, only the small and medium size classes migrated, on average 0.85 m h-1, corresponding to a total migration distance of 10 m during 12 h. Larger individuals (with well developed lobes, approx. >27 mm) stay on average in the same depth interval at all times. Biophysical data suggest that migrating individuals likely responded to light, and avoided irradiance levels higher than approx. 10 µmol quanta m-2 s-1. We suggest that strong stratification caused by low surface salinity seemed to prohibit vertical migration.
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| 24. |
- Hosia, A., et al.
(författare)
-
Seasonal abundance and vertical distribution of siphonophores in western Norwegian fjords
- 2008
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 30:8, s. 951-962
-
Tidskriftsartikel (refereegranskat)abstract
- Seasonal abundance of siphonophores in Korsfjord and Fanafjord was studied by net sampling. Nanomia cara, Lensia conoidea and Dimophyes arctica were dominant species present throughout the year. Abundance of N. cara colonies peaked in late May and early June. Low numbers of relatively large colonies and high numbers of siphonulae were observed during winter. Dimophyes arctica and L. conoidea had a generation shift in March, when large over-wintering and small young polygastric colonies co-existed briefly before the former disappeared. Abundances were lowest during winter, and eudoxids were consistently more numerous than polygastric colonies for both species. Maximum abundances of polygastric D. arctica and L. conoidea occurred in early May and late June, respectively. Lensia conoidea may have more than one annual generation in Korsfjord. Vertical distributions of siphonophores were studied with an remotely operated vehicle in nine fjords. The distributions of agalmatid physonects, probably mostly N. cara, differed significantly between the fjords, with the weighted mean depths of the distributions ranging from 99 to 412 m. Results from Sognefjord suggested diel vertical migration. The bulk of the adult colonies in each fjord occurred below sill depth. Siphonophores were not observed at localities known to host persistent populations of Periphylla periphylla.
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| 25. |
- Hosia, A., et al.
(författare)
-
Seasonal changes in the gelatinous zooplankton community and hydromedusa abundances in Korsfjord and Fanafjord, western Norway
- 2008
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 351, s. 113-127
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative seasonal studies on gelatinous zooplankton in Norwegian fjords are scarce. We recorded the quantitative composition of the gelatinous zooplankton community in Korsfjord and Fanafjord during 1 yr. Thirty-six species or genera of hydromedusae, 7 species of siphonophores, 4 species of ctenophores and 2 species of scyphomedusae were recorded. Aglantha digitale was numerically dominant in both fjords. A separate video-profiling study on the vertical distribution of fully grown specimens of this species was made in Korsfjord and the adjacent Bjornafjord. Our data suggest 2 A. digitale generations yr(-1), with relatively low importance of the latter generation. The overwintering strategy includes autumn growth to full size and distribution at intermediate depth, mainly between 200 and 300 m. Siphonophores were prominent in the more oceanic Korsfjord, while Fanafjord was characterized by meroplanktonic hydromedusae. More species were recorded from Korsfjord, which may be partly attributed to the larger volume sampled and the higher probability of encountering oceanic visitors in this fjord. Korsfjord also harbored a community of deep-water hydromedusae absent from Fanafjord. The gelatinous community of both fjords was most numerous and species-rich from April to June. Spring maximum densities were higher in Fanafjord. During winter, gelatinous zooplankton was more abundant in Korsfjord, with eudoxids of Dimophyes arctica and Lensia conoidea forming the bulk of the community. Hydromedusa species appeared sequentially and differed in terms of maximum abundance attained and length of their presence in the plankton. Multivariate analyses revealed a clear seasonal succession for the gelatinous community of both fjords.
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| 26. |
- Kuismanen, Lauri, et al.
(författare)
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Salinity effects on egg production, hatching, and survival of Eurytemora affinis (Copepoda, Calanoida)
- 2020
-
Ingår i: Proceedings of the Eurytemora conference, St. Petersburg, 2019. - : Brill Academic Publishers. ; , s. 429-445
-
Konferensbidrag (refereegranskat)abstract
- Salinity is an important biodiversity regulating factor in the Baltic Sea, forming a physiological dispersal barrier for species. The salinity in the Baltic Sea has been predicted to decline due to increased precipitation and fewer saline water inflows from the ocean. This causes stress to species already living on the edge of their tolerances and can alter species compositions and interactions in ecosystems. Calanoid copepod resting eggs, originating from a known egg bank on the seabed in the western Gulf of Finland, were incubated in the laboratory. We monitored the hatching of the calanoid copepods Acartia sp. and Eurytemora affinis, as well as the survival to maturity of hatched Eurytemora affinis nauplii in salinities ranging from 0 to 25. Further, we also investigated salinity-related effects on body size and egg production. Based on the results of our generalized linear mixed model, peak hatching occurred within the salinity range 5-20 (6.3 at the study site). Body size was not affected by salinity and most eggs were produced in salinities of 5, 7.5 and 15. The results suggest that E. affinis lives on the edge of an optimal salinity and that a decline of salinity could affect the fitness of the local populations of the species.
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| 27. |
- Lefébure, Robert, 1980-
(författare)
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Effects of temperature and terrestrial carbon on fish growth and pelagic food web efficiency
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Both temperature and terrestrial dissolved organic carbon (TDOC) have strong impacts on aquatic food web dynamics and production. Temperature affects vital rates of all organisms and terrestrial carbon has been shown to alter the dynamics of phytoplankton and bacterial production and affect the trophic structure of planktonic food webs. As climate change predictions for the Baltic Sea suggests future increases in both terrestrial carbon run-off and increases in temperature, the aim of thesis was to adopt a system-ecological approach and study effects of these abiotic variables, not only on interactions within planktonic food webs, but also on the growth and consumption rates of one of the most common zooplanktivorous fish in the Baltic Sea, the three-spined stickleback Gasterosteus aculeatus. Results showed that three-spined sticklebacks display a high degree of resilience against increasing temperatures, as both growth rates as well as consumption rates on zooplankton were high at temperatures well over 20 °C. Furthermore, it was shown that the minimal resource densities required to sustain individual and population growth, actually decreased with increasing temperatures, implying that sticklebacks around their optimum temperature for growth at 21 °C will actually have an increased scope for growth. As stickleback population densities have increased over the last decade in the Baltic Sea and are now suggested to out-compete other coastal fish species for shared zooplankton resources, the results presented in this thesis suggest that increased water temperatures would only serve to increase sticklebacks competitive advantage. As the structuring role of this small zooplanktivore on pelagic communities might be considerable, further studies investigating competitive interactions as well as patterns of population abundances are definitely warranted. TDOC was overall shown to stimulate bacterial production and the microbial food web. Because of the longer trophic pathways required to transport carbon from bacterial production to higher trophic levels, the addition of TDOC always reduced food web transfer efficiency. However, it became apparent that the full effect of TDOC additions on pelagic food webs was complex and depended heavily not only on the existing trophic structure to which the carbon was introduced, but also on ambient temperature levels. When three-spined sticklebacks were part of food webs with significant TDOC inputs, the presence of fish, indirectly, through predator release of lower trophic levels, amplified the magnitude of the effects of carbon addition on bacterial production, turning the base of the system significantly more heterotrophic, which ultimately, impacted negatively on their own production. However, when a pelagic food web containing sticklebacks was simultaneously subjected to realistic increases in temperature and TDOC concentrations, food web efficiency and fish production increased compared to present day conditions. These results were explained by a temperature dependent increased production potential of zooplankton, sustained by an increased production of heterotropic microzooplankton via TDOC additions, which lead to higher fish production. Although the increased number of trophic linkages in heterotrophic food webs should have reduced energy transfer efficiency, these negative effects seem here to have been overridden by the positive increases in zooplankton production as a result of increased temperature. These results show that heterotrophic carbon transfer can be a viable pathway to top-consumers, but also indicates that in order to understand the full effects of climate change on trophic dynamics and fish production, abiotic variables cannot be studied in isolation.
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| 28. |
- Lefebure, Robert, et al.
(författare)
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Impacts of elevated terrestrial nutrient loads and temperature on pelagic food-web efficiency and fish production
- 2013
-
Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 19:5, s. 1358-1372
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Both temperature and terrestrial organic matter have strong impacts on aquatic food-web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food-web dynamics and food-web efficiency in a plausible future scenario with respect to these abiotic variables in a large-scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food-web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food-web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web.
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| 29. |
- Md Amin, Roswati, 1983-
(författare)
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Copepods in Skeletonema-dominated food webs : Toxicity and nutritional quality as factors controlling copepod-diatom interactions
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- My thesis focuses on copepod-diatom interactions, specifically on the effects of food quality and toxicity on copepod feeding, reproductive success and behavior but as a frame, also includes a quantitative evaluation of copepod carbon requirements compared to other trophic plankton groups. My aim was to evaluate the function of copepods in diatom-dominated spring blooms. I thereby used a series of mesocosm and laboratory experiments. For a realistic extrapolation of the results to natural environments I used different strains of a diatom species, Skeletonema marinoi, which is a common spring blooming species in the Baltic Sea. This species is known to produce polyunsaturated aldehydes (PUA; mainly heptadienal, octadienal and decadienal), which have previously been identified as the potential reasons for the detrimental effects of diatoms on copepod reproduction. All strains varied in size, mineral and biochemical content, and PUA production. I tested the effects on different dominant copepod species from northern temperate waters; Acartia sp. (A. clausi and A. tonsa), Calanus finmarchicus, Pseudocalanus elongatus, and Temora longicornis, as well as the dominant species in the northern Baltic Sea, Eurytemora affinis. The specific contributions of respiratory carbon requiment of mesozooplankton and lower size fractions to carbon cycling during PUA-producing diatom blooms are poorly documented. My results show that nanoplankton and microzooplankton dominated the carbon cycling (> 50% of primary production) whereas the contribution of bacterioplankton varied. Mesozooplankton was always of minor importance with contribution of <6% of primary production. This illustrates the importance of lower size fractions during a phytoplankton spring bloom. Irrespective of their small contribution to the total community carbon cycling, copepods displayed non-selective and typically high feeding rate on different PUA-producing S. marinoi strains, indicating that there was no feeding deterrence. The effect of feeding on copepod reproductive success, however, varied between different strains, and depending on copepod species. In experiments with monospecific diatom diets reduced egg production rate and hatching success were mainly related to food quality measured as fatty acids and sterols, or algae growth rate, low assimilation efficiency or PUA production / ingestion. On the other hand, copepod reproduction and population development in the diverse diet, including a high concentration of S. marinoi and PUA (both particulate and dissolved), increased with increasing food concentration and was unaffected by the presence of toxic diatoms. I conclude that although a negative correlation between different reproductive variables and PUA production / ingestion may sometimes be observed in laboratory incubations, this is highly dependent on the strain / species used, and the effect of the algal strain can be stronger than the effect of the e.g., growth-stage dependent PUA production. Although copepod grazing might not be very important during a diatom spring bloom, even a highly PUA-producing S. marinoi can be considered an appropriate food source for copepods when occurring among the natural food assemblage, inducing a high reproductive output.
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| 30. |
- Md Amin, Roswati, et al.
(författare)
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Partition of planktonic respiratory carbon requirements during a phytoplankton spring bloom
- 2012
-
Ingår i: Marine Ecology Progress Series. - : Inter-research. - 0171-8630 .- 1616-1599. ; 451, s. 15-29
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the effect of variable phytoplankton biomass and dominance of the diatom Skeletonema marinoi on the planktonic community respiratory carbon requirement over a period of 14 days (14-28 April, 2008) in 3 different mesocosms filled with natural water at Espegrend marine biological field station by Raunefjord, Norway. The carbon requirement was measured on mesozooplankton (the calanoid copepod Calanus finmarchicus) and three different size fraction; <200 µm (dominated by microzooplankton), <15 µm (dominated by nanoplankton including most of the phytoplankton) and particles passing GF/C (dominated by bacterioplankton) by measuring oxygen consumption with an optode system with two SensorDish Readers. The respiratory carbon requirement showed no clear trend over time for any of the four groups. The mesozooplankton contributed the least to the total community carbon requirement, corresponding to less than 6% of primary production. In contrast, microzooplankton and nanoplankton consistently dominated the community carbon requirement, corresponding to > 50% of the primary production, while bacterioplankton showed an intermediate and variable contribution (ca <20% with a max of 50%). Feeding experiments on mesozooplankton (C. finmarchicus) two days before the peak in phytoplankton biomass, showed that the copepods ingested 2.4-4.3 times their respiratory carbon requirements, thus giving a high potential for growth. Respiratory carbon requirements of mesozooplankton were not significantly related to dominance or quantity of food available, whereas the respiratory carbon requirements of other groups were all related to the production of 22:6(n-3) fatty acid. The study confirms the important role of microorganisms in the biological carbon transformation through the food web during a phytoplankton spring bloom.
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| 31. |
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| 32. |
- Olsen, Bernt Rydland, et al.
(författare)
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PCR-DHPLC assay for the identification of predator-prey interactions
- 2012
-
Ingår i: Journal of Plankton Research. - Oxford : Oxford University Press. - 0142-7873 .- 1464-3774. ; 34:4, s. 277-285
-
Tidskriftsartikel (refereegranskat)abstract
- Denaturing high-performance liquid chromatography (DHPLC) is a relatively new method for separating amplicons in a mixture, and was recently developed for parasite detection in the blue crab Callinectes sapidus. That assay used a peptide nucleic acid (PNA) PCR hybridization blocking probe (PNAPCRDHPLC) to decrease the generic PCR bias of dominant templates (the host) in the mixture prior to separation on the DHPLC column, thus enhancing the less abundant parasite DNA. The same assay and rational can be used to investigate predatorprey interactions. However, in ecosystem studies with many predatorprey relationships, development of specific PNA-blocking probes for each predator would be too laborious. Here, we have developed a PCRDHPLC assay excluding the dominant predator amplicons in a first DHPLC run, followed by re-amplification of the non-predator retention volumes and further separation and characterization in a second DHPLC run. This assay generated data on the specific trophic interactions between the calanoid copepod Limnocalanus macrurus and its prey from a seasonal sampling programme. The assay provides an efficient way for an unbiased screening of predatorprey relationships, and although developed for L. macrurus in this study, the approach has wide applicability for any predatorprey interaction.
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| 33. |
- Sjoqvist, C., et al.
(författare)
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Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population
- 2014
-
Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 67:1, s. 83-95
-
Tidskriftsartikel (refereegranskat)abstract
- Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.
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| 34. |
- Sornes, T.A., et al.
(författare)
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Swimming and feeding in Periphylla periphylla (Scyphozoa, Coronatae)
- 2008
-
Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 153:4, s. 653-659
-
Tidskriftsartikel (refereegranskat)abstract
- Some western Norwegian fjords host extraordinarily abundant and persistent populations of the mesopelagic, coronate scyphomedusa, Periphylla periphylla. In these environments, from late autumn to spring, the medusae undertake regular diel vertical migrations into surface waters. From unique observations obtained with a remotely operated vehicle (ROV), including observations made without artificial light, we observed that 90% of the medusae swam with their tentacles in aboral position. Stomach content analyses of surface-collected specimens revealed that the medusae ate mainly calanoid copepods, but ostracods and large euphausiids were also prominent components of their diets. The clearance rate potential of P. periphylla, assessed from in situ observations and stomach contents, was comparable to that of similar-sized, epipelagic gelatinous species. Our findings suggest that P. periphylla behave as active predators in surface waters.
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| 35. |
- Sotje, I., et al.
(författare)
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Trophic ecology and the related functional morphology of the deepwater medusa Periphylla periphylla (Scyphozoa, Coronata)
- 2007
-
Ingår i: Marine Biology. - 0025-3162 .- 1432-1793. ; 150:3, s. 329-343
-
Tidskriftsartikel (refereegranskat)abstract
- Remotely operated vehicle (ROV)-based field studies on the distribution and behaviour of Periphylla periphylla Péron and Lesueur (Ann Mus Hist Nat Marseille 14:316-366, 1809), from three Norwegian fjords have been combined with on-board experiments and morphological and histological studies in order to understand the trophic ecology of this species. Field studies from one of the fjords showed that the zooplankton biomass was negatively related with P. periphylla abundance, indicating a predatory effect. The majority of zooplankton biomass tended to be distributed above the aggregation of P. periphylla, which in turn showed highest abundance at 100-200 m depth. Observation on the orientation of medusae passing the ROV when descending down in the water column at dawn and dusk, showed no consistency with the theory of diel vertical migration. Estimated metabolic demand of P. periphylla indicated a daily predation impact on the prey assemblage of 13% as an average for the fjord. In situ behavioural observations showed that the dominant tentacle posture of large medusae was straight upward, with tentacles extended to the oral-aboral body axis. The hunting mode alternates between ambush and ramming, whereby tentacle posture minimises the water turbulence that may otherwise alarm the prey. The musculature of the tentacles is well developed, with an especially strong longitudinal muscle on the oral side, facilitating fast movement of the tentacle towards the mouth. In addition, ring-, radial-, and diagonal musculatures are also present. The diagonal is probably most important for the corkscrew retraction of the tentacle, used at the moment of prey capture. Results from laboratory experiments show that different body-parts of P. periphylla vary in sensitivity for chemical and mechanical stimuli, including hydrodynamic disturbance and vibration in the surrounding water. Feeding success is facilitated by combining the vibration-sense on the tentacle tips and the marginal lappets, the touch-sense on the tentacle bases and marginal lappets, and a taste control of the captured prey at the mouthlips.
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| 36. |
- Van Nieuwerburgh, Lies, 1973-
(författare)
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Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines the role of dissolved inorganic nutrients in generating changes in phytoplankton community and pigment composition and if such changes can affect the production of the antioxidant astaxanthin in the ecosystem via pelagic copepods. The background of my studies is the possible relationship between eutrophication and a reproductive disturbance in Baltic populations of Atlantic salmon (M74), which is associated with astaxanthin and thiamine deficiencies and oxidative stress. In the southern Baltic Sea, changes in nutrient loads correlate with observed trends of flagellates replacing diatoms in the phytoplankton. Copepods are the main producers of astaxanthin and a major link between phytoplankton and higher trophic levels. In laboratory and field experiments in the Baltic Sea proper and the Norwegian Sea, I show that astaxanthin synthesis in copepods is fast and depends on pigment composition of the phytoplankton diet. Among single-species diets, a diatom and a green algal cyst yielded the highest astaxanthin levels in copepods, and another diatom species, a green alga and a cyanobacterium the lowest. In nutrient-generated phytoplankton blooms in mesocosms, copepods grazing on diverse communities dominated by weakly silicified diatoms produced more astaxanthin compared with copepods grazing on communities dominated by strongly silicified diatoms. This suggests that diatoms invested in defence mechanisms and escaped grazing at surplus Si. A nutrient-starved diatom culture subjected to intraspecific competition exhibited decreased pigment levels, increased thiamine levels and increased oxidative stress. My results suggest that diatoms are beneficial for astaxanthin and thiamine production compared to other phytoplankton groups, but not under all circumstances. Copepod growth and development also responded to inorganic nutrient availability and affected total astaxanthin production per volume seawater, with highest production when the copepods grazed on diatoms. From an ecosystem perspective, increased N and P loads seem to promote high astaxanthin production, but not when diatoms disappear completely.
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| 37. |
- Voigt, Thiemo, et al.
(författare)
-
Sensor Networking in Aquatic Environments - Experiences and New Challenges
- 2007. - 1
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Konferensbidrag (refereegranskat)abstract
- In this paper we present the design and implementation of a small-scale marine sensor network. The network monitors the temperature in the Baltic Sea on different heights from the water surface down to the bottom. Unlike many other wireless sensor networks, this network contains both a wired and a wireless part. One of the major challenges is that the network is hard to access after its deployment and hence both hard- and software must be robust and reliable. We also present the design of an advanced buoy system featuring a diving unit that achieves a better vertical resolution and discuss remaining challenges of sensor networking in aquatic environments.
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| 38. |
- Wikner, Johan, 1961-, et al.
(författare)
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Precise continuous measurements of pelagic respiration in coastal waters with Oxygen Optodes
- 2013
-
Ingår i: Limnology and Oceanography. - : Association for the Sciences of Limnology and Oceanography. - 1541-5856. ; 11, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical setup for respiration rate measurements was developed and evaluated in pelagic water samples using a commercially available optical oxygen sensor (Optode (TM)). This setup required the development of a gas tight stopper to connect the sensors to a 1 dm(3) glass sample bottle, precise temperature control (+/- 0.05 degrees C), and proper stirring of samples. The detection limit and precision of the method was 0.3 mmol O-2 m(-3) d(-1). This was similar to the detection limit for the high-precision Winkler titration method reported in field studies. When compared with the Winkler method, the Optode sensor enabled operator-independent, high temporal resolution measurement of respiration, better coverage of plankton groups and detection of non-linear oxygen decline, without the need for wet chemistry. Respiration rates measured by the Optodes showed good accuracy when compared with measurements made with the Winkler titration method (3% deviation), followed the expected temperature response (Q(10) = 3.0), were correlated with chlorophyll a and were congruent with earlier reported values in the literature. The main source of uncertainty was a necessary correction for system drift during the incubation period, due to oxygen release from the plastic components. Additionally, less stringent temperature control on board research vessels during rough seas reduced the precision. We conclude that the developed Optode system can be used to measure respiration in productive coastal waters. Samples from cold or deep waters were, however, often below the detection limit.
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| 39. |
- Wikner, Johan, Professor, 1961-, et al.
(författare)
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Report on boundary conditions for winter mesocosms
- 2023
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ongoing climate change is projected to extend the warmer and therefore the biologically productive season, reducing ice cover, ice thickness, and quality, potentially influencing biodiversity, and productivity of aquatic ecosystems. Changed influence of dissolved organic matter is one factor that can contribute to those effects. Winter ecology is little studied, and the advancement of knowledge would benefit from controlled experiments on the mesocosm scale. To investigate the capability of mesocosm experimental infrastructures for winter ecological research, a 5-months long experiment during the sub-arctic winter in 2021/2022 was conducted in Umeå, Sweden. Simultaneously, the performance of an outdoor and indoor mesocosm facility with ice-forming capability at the same site was compared. Boundary conditions for hydrographic, chemical, and biological variables were determined.The facilities were operated successfully over winter and treatments caused similar effects in both systems, despite some differences presented below. Salinity and temperature were similar between the facilities throughout the experiment. Ice was markedly thicker on the sea compared to in the indoor facility. Further the ice inside the outdoor mesocosms, was significantly thicker than on the surrounding natural sea. Light irradiance indoors correlated with the outdoor facility, but light irradiance indoors could not reach the outside values in the lightest months of the experiment (after mid-March). Both dissolved organic carbon and dissolved nitrogen was higher in the outdoor facility, possibly caused by a pump effect increasing organic carbon and nitrogen concentrations. Most other nutrient levels remained similar. Chlorophyll-a was comparable between the facilities, while plankton respiration was twice the rate outdoors compared to indoors. Two substances were used to simulate browning, HuminFeed® (a commercially available leonardite) and soil extract, causing similar treatment effects in both facilities for 75% of measured variables. HuminFeed caused a marked increase in CDOM (coloured dissolved organic matter) and nitrite during spring. Treatment with soil extract resulted in slightly higher phosphorus concentrations.The indoor mesocosm facility was thus comparable to the outdoor facility regarding experimental effects, despite facility differences observed. The organic matter sources HuminFeed and soil extract differ in some experimental effects that need to be considered. These results should provide basic knowledge for improving experimental design in future winter mesocosm studies.
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| 40. |
- Winder, Monika, et al.
(författare)
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Increased appendicularian zooplankton alter carbon cycling under warmer more acidified ocean conditions
- 2017
-
Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 62:4, s. 1541-1551
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Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications.
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