SwePub
Sök i SwePub databas

  Extended search

Träfflista för sökning "L773:0142 7873 OR L773:1464 3774 "

Search: L773:0142 7873 OR L773:1464 3774

  • Result 1-50 of 99
Sort/group result
   
EnumerationReferenceCoverFind
1.
  • Alonso-Saez, Laura, et al. (author)
  • Changes in marine prokaryotic community induced by varying types of dissolved organic matter and subsequent grazing pressure
  • 2009
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 31:11, s. 1373-1383
  • Journal article (peer-reviewed)abstract
    • We analysed changes in the abundance, biomass, activity and composition of coastal marine prokaryotic communities after the addition of organic substrates, such as glucose, leucine and yeast extract, and the effect of grazing pressure exerted by nanoflagellates. The addition of a carbon source (i.e. glucose) promoted the growth of Gammaproteobacteria, while a combined source of C and N (i.e. leucine) favoured the development of Alphaproteobacteria. The addition of yeast extract, a complex substrate rich in N and growth factors, promoted the proliferation of Alphaproteobacteria and Gammaproteobacteria. Grazing pressure exerted by nanoflagellates produced marked differences on the size structure of the prokaryotic biomass. A pronounced tendency to filamentation and aggregation was observed in the glucose treatment, while in the case of yeast extract, small and mainly freely dispersed prokaryotes were maintained throughout the incubations. Thus, the final community in the yeast extract treatment showed a high percentage of edible biomass, while an important fraction of potentially grazing-resistant prokaryotes (more than 50% of total prokaryotic biomass) was detected in the microcosms enriched with glucose. These results suggest a marked effect of DOM sources on the development of grazing-resistant prokaryotes.
  •  
2.
  • Berggren, Martin, et al. (author)
  • Toward an ecologically meaningful view of resource stoichiometry in DOM-dominated aquatic systems
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:3, s. 489-499
  • Journal article (peer-reviewed)abstract
    • Research on nutrient controls of planktonic productivity tends to focus on a few standard fractions of inorganic or total nitrogen (N) and phosphorus (P). However, there is a wide range in the degree to which land-derived dissolved organic nutrients can be assimilated by biota. Thus, in systems where such fractions form a majority of the macronutrient resource pool, including many boreal inland waters and estuaries, our understanding of bacterio-and phytoplankton production dynamics remains limited. To adequately predict aquatic productivity in a changing environment, improved standard methods are needed for determining the sizes of active (bioavailable) pools of N, P and organic carbon (C). A synthesis of current knowledge suggests that variation in the C:N:P stoichiometry of bioavailable resources is associated with diverse processes that differentially influence the individual elements across space and time. Due to a generally increasing organic nutrient bioavailability from C to N to P, we hypothesize that the C:N and N:P of bulk resources often vastly overestimates the corresponding ratios of bioavailable resources. It is further proposed that basal planktonic production is regulated by variation in the source, magnitude and timing of terrestrial runoff, through processes that have so far been poorly described.
  •  
3.
  • Berglund, Johnny, et al. (author)
  • Relative strength of resource and predation limitation of heterotrophic nanoflagellates in a low-productive sea area
  • 2005
  • In: Journal of Plankton Research. - London : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:9, s. 923-935
  • Journal article (peer-reviewed)abstract
    • The magnitude of resource and predation limitation of heterotrophic nanoflagellales (HMF) was studied in two short-term enclosure experiments performed in a low-productive sea area in the northern Baltic Sea in 2001. A cross-factorial design was used to simultaneously assess the relative importance of the two factors. Resource limitation was removed by adding bacteria, and predation limitation was eliminated by selective filtration. The first experiment was performed in June just after the spring bloom decline and the second in September at the end of the productive season. Resource limitation prevailed during both experiments, contributing to 60% of the net growth increase in June and 74% in September. Removal of predators had a significant effect only in June. Evidence for simultaneous resource and predation limitation was thus found only during the post-bloom situation. The results were applied to a model on resource and predation control of HNF abundances. To evaluate seasonal differences, field data on HNF and bacteria from a whole year study were applied to the model. Except for a few occasions during spring, the model indicated prevailing resource control of HNF at two locations with slightly different productivity. © The Author 2005. Published by Oxford University Press. All rights reserved.
  •  
4.
  • Bertilsson, S, et al. (author)
  • Size-selective predation on pelagic microorganisms in Arctic freshwaters
  • 2003
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 25:6, s. 621-631
  • Journal article (peer-reviewed)abstract
    • Herbivorous zooplankton may have a pronounced influence on pelagic microorganisms in Arctic freshwaters. We quantified experimentally the size-selective feeding of several zooplankton groups on pelagic microorganisms in high Arctic tundra systems. Our experiments and field study focused on dominant herbivores in Arctic freshwaters, including the cladoceran Dophnia, the copepod Diaptomus and the anostracan Branchinecta, and their effects on prey ranging in size from bacteria to large phytoplankton. Grazing experiments showed that Dophnia were effective predators on all types of prey, whereas Diaptomus grazed preferentially on larger phytoplankton with low clearance rates for bacterial cells. Further analysis by flow cytometry indicated that Diaptomus grazed selectively on the largest bacteria. In contrast to the results obtained in the controlled experiments, Arctic lakes and ponds with a zooplankton community dominated by Dophnia had a higher bacterial production and abundance than systems not dominated by this grazer. This may indicate that the stimulatory effect of grazers on bacterial growth is more pronounced in natural systems, or that factors other than zooplankton grazing are more important in regulating bacterial abundance and production in natural systems. Although Arctic waters differ considerably from temperate systems with respect to temperature and light regime, herbivore-prey dynamics as well as the bacterial response to temperature appear to be similar between the climatic regions.
  •  
5.
  • Bjærke, Oda, et al. (author)
  • Is chain length in phytoplankton regulated to evade predation?
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:6, s. 1110-1119
  • Journal article (peer-reviewed)abstract
    • Formation of cell chains in phytoplankton is ecologically important, but no single factor driving the evolution of chain formation has been identified. Chain length in the diatom Skeletonema marinoi declines in response to grazer cues, which reduces grazing losses in simple laboratory incubations. Here we explore a more ecologically relevant scenario with fluctuating populations of different sized grazers, and test whether chain-length plasticity provides a selective advantage by lower grazing mortality. We used a model with empirical grazer densities, the effect of grazer cues on chain length, and size selective grazing rates. Finally we compared the model outcome with Skeletonema chain length and copepod biomass in the field. Low copepod densities induced chain-length reduction in Skeletonema, showing that the signaling system is sensitive enough to operate in nature. The model shows that reducing chain length in response to copepod cues reduces annual grazing losses by 31 and 36% compared with fixed traits with either single cells or long chains, respectively. The field measurements agree well with chain length being regulated by grazer abundances. We conclude that chain-length plasticity is a selective trait, and suggest that grazer regime could be an evolutionary driver of chain formation in phytoplankton.
  •  
6.
  • Bolton, T. F., et al. (author)
  • Physiological acclimation to decreased water temperature and the relative importance of water viscosity in determining the feeding performance of larvae of a serpulid polychaete
  • 2005
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:9, s. 875-879
  • Journal article (peer-reviewed)abstract
    • Ambient temperature exerts both physiological and mechanical effects on the rates of functional processes of small aquatic ectotherms. Physiological effects of temperature result from its influence on the rates of chemical reactions. Mechanical effects of temperature result from the inverse relationship between the temperature of water and its dynamic viscosity. We measured the relative importance of these components of temperature on the feeding performance of polychaete larvae. Cohorts of larvae were reared for 24 h at 20 degrees C and 10 degrees C in treatments where the physiological and mechanical effects of these temperatures were separated. The feeding performance of these larvae was subsequently measured in treatments where these components of temperature were similarly partitioned. Cold-reared larvae displayed complete acclimation of feeding performance to the physiological effects of decreased temperature: thus, increased viscosity was responsible for 100% of the difference in feeding performance between 20 degrees C and 10 degrees C. The physiological ability of small aquatic ectotherms to acclimate functional processes to temperature variation may be greater than previously thought, and these results have implications for understanding the responses of aquatic ectotherms' to global temperature change.
  •  
7.
  •  
8.
  • Båmstedt, Ulf, et al. (author)
  • Fecundity and early life of the deep-water jellyfish Periphylla periphylla
  • 2020
  • In: Journal of Plankton Research. - : OXFORD UNIV PRESS. - 0142-7873 .- 1464-3774. ; 42:1, s. 87-101
  • Journal article (peer-reviewed)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.
  •  
9.
  • Carey, Cayelan C., et al. (author)
  • The cyanobacterium Gloeotrichia echinulata stimulates the growth of other phytoplankton
  • 2010
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 32:9, s. 1349-1354
  • Journal article (peer-reviewed)abstract
    • We tested the effect of the cyanobacterium Gloeotrichia echinulata on a diverse array of phytoplankton. We found that Gloeotrichia increased the growth rates of five of seven phytoplankton species up to 620% in comparison with a medium-only control after 96 h.
  •  
10.
  • Chauton, M, et al. (author)
  • Changes in pigmentation, bio-optical characteristics and photophysiology, during phytoflagellate succession in mesocosms
  • 2004
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 26:3, s. 315-324
  • Journal article (peer-reviewed)abstract
    • Pigmentation, bio-optical characteristics and photophysiology, were studied in mesocosms with different N:P ratios. No significant difference in biomass or species composition was seen under different nitrogen to phosphorus ratios (N:P), but a temporal succession of different flagellate groups was observed in all mesocosms. An initial bloom of prymnesiophytes containing chlorophyll (Chl) c and 19' hexanoyloxyfucoxanthin (19' HOF) was followed by prasinophytes containing Chl b. Electron microscope analysis confirmed the presence of genera such as Chrysochromulina (Prymnesiophyceae), Tetraselmis and Pyramimonas (Prasinophyceae). Traces of prasinoxanthin in the pigment samples showed that smaller prasinophytes were also present. Chl b influenced the photophysiology of the prasinophytes resulting in higher Chl a-specific absorption, but a greater difference between absorption and scaled fluorescence excitation spectra indicated that light absorbed by Chl b is associated with photosystem I (PSI). Since a larger fraction of the light was absorbed by chlorophyll in PSI and/or photoprotective carotenoids, the light-saturated Chl a-specific rate of photosynthesis (P-m(B)) and maximum light utilization coefficient (alpha(B)) decreased when [Chl b] increased. The highest P-m(B) values were seen when the ratios of fucoxanthins to Chl a were high, indicating that prymnesiophytes might be more efficient in light harvesting and electron transport through photosystem II (PSII) by fucoxanthins and Chl c. Our results therefore indicate different light acclimation strategies in prasinophytes versus prymnesiophytes, which may be reflected in the successional appearance of these communities in the natural environment. We also suggest that grazing by ciliates and rotifers caused periodic decreases in phytoplankton biomass, which in turn gave rise to the phytoflagellate succession observed in the mesocosms.
  •  
11.
  • Dahlgren, Kristin, et al. (author)
  • Seasonal variation in wax ester concentration and gut content in a Baltic Sea copepod [Limnocalanus macrurus (Sars 1863)]
  • 2012
  • In: Journal of Plankton Research. - Oxford : Oxford University Press. - 0142-7873 .- 1464-3774. ; 34:4, s. 286-297
  • Journal article (peer-reviewed)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.
  •  
12.
  • Degerlund, Maria, et al. (author)
  • Functional diversity in cryptic species of Chaetoceros socialis Lauder (Bacillariophyceae)
  • 2012
  • In: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 34:5, s. 416-431
  • Journal article (peer-reviewed)abstract
    • The cosmopolitan distribution of the marine planktonic diatom Chaetoceros socialis Lauder is generally interpreted as a case of wide ecological plasticity. However, cryptic diversity has recently been observed within this taxon and this genetic diversity could extend to phenotypic differences between allopatric populations. Monoclonal strains of C. socialis isolated from NE Atlantic/Arctic and Tyrrhenian Sea waters were cultivated at 2.5, 8 and 13°C, and analysed for morphological, phylogenetic (LSU rRNA gene) and physiological (growth rate, photosynthetic yield) traits. The molecular analysis indicated an unequivocal divergence between the southern and the northern strains. Clear differences in spore morphology between the two groups were also observed, despite their morphological similarity in vegetative form. The physiological data demonstrated a functional partition between the northern and southern strains. The northern strains showed significantly higher growth rates than the southern ones at the lower temperatures, and vice versa at 13°C. Differences between the groups were also observed in the photosynthetic yields. These results reveal the expression of allopatric speciation in several phenotypic characters, providing a functional dimension to the cryptic, or rather pseudo-cryptic, diversity observed within C. socialis. We believe that such an integrated approach is useful for robust taxonomic and functional delimitations of presumed cosmopolitan microorganisms.
  •  
13.
  • Ekelund, Nils, 1956- (author)
  • The effect of UV-B radiation and humic substances on growth and motility of the flagellate, Euglena gracilis.
  • 1993
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 15, s. 715-722
  • Journal article (peer-reviewed)abstract
    • The effects of ultraviolet-B radiation (UV-B, 250–315 nm) were determined on Euglena gracilis with respect to speed, phototactic orientation, specific growth rate, and in the presence of humic substances. Humic substances had a protective effect when studying the speed and specific growth rate. However, the degree of phototactic orientation decreased in UV-B radiation both with and without humic substances. The inhibition of O2 evolution and speed was most pronounced when using cutoff filters WG280 and WG295. The photosynthetic inhibitor DCMU (10–6 M) did not have any effect on the speed, but the 02 evolution decreased to zero. The effect of different wavelengths in the UV-B region on the speed of E.gracilis showed the maximum sensitivity at 280 and 290 nm.
  •  
14.
  • Engström-Öst, Jonna, et al. (author)
  • Consequences of a cyanobacteria bloom for copepod reproduction, mortality and sex ratio
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:2, s. 388-398
  • Journal article (peer-reviewed)abstract
    • The aim of the study was to measure copepod reproduction, mortality and sex ratio in the field before, during and after a cyanobacteria bloom during the summer in the western Gulf of Finland. Environment and zooplankton samples were collected every fortnight, and the copepod Acartia spp. was incubated in the laboratory for reproductive output, i.e. egg production and egg hatching success. Other responses monitored were female: male ratio, mortality and body condition. In addition, molecular analyses of the nodularin-producing cyanobacterium Nodularia in Acartia gut contents (GCs) were assessed. Egg production and body condition decreased with increasing Nodularia GCs. During the bloom, hatching decreased as a response to Nodularia in the copepod gut. Although not related to cyanobacteria variables, male mortality was higher than female mortality, resulting in a female-biased sex ratio over most of the summer. The study demonstrates that Acartia reproductive output is constrained by cyanobacteria blooms in the Baltic Sea, and more generally that copepod population dynamics may be negatively affected by such blooms. This is especially significant considering that toxin-producing blooms are predicted to increase due to warming.
  •  
15.
  • Flynn, Kevin J, et al. (author)
  • Misuse of the phytoplankton-zooplankton dichotomy : the need to assign organisms as mixotrophs within plankton functional types
  • 2013
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 35:1, s. 3-11
  • Journal article (peer-reviewed)abstract
    • The classic portrayal of plankton is dominated by phytoplanktonic primary producersand zooplanktonic secondary producers. In reality, many if not most planktontraditionally labelled as phytoplankton or microzooplankton should be identifiedas mixotrophs, contributing to both primary and secondary production. Mixotrophicprotists (i.e. single-celled eukaryotes that perform photosynthesis and grazeon particles) do not represent a minor component of the plankton, as some formof inferior representatives of the past evolution of protists; they represent a majorcomponent of the extant protist plankton, and one which could become moredominant with climate change. The implications for this mistaken identification, ofthe incorrect labelling of mixotrophs as “phytoplankton” or “microzooplankton”,are great. It extends from the (mis)use of photopigments as indicators of primaryproduction performed by strict photoautotrophs rather than also (co)locating mixotrophicactivity, through to the inadequacy of plankton functional type descriptionsin models (noting that mixotrophic production in the individual organism is not asimple sum of phototrophy and heterotrophy). We propose that mixotrophy shouldbe recognized as a major contributor to plankton dynamics, with due effortexpended in field and laboratory studies, and should no longer be side-lined inconceptual food webs or in mathematical models.
  •  
16.
  • Fridolfsson, Emil, et al. (author)
  • Limited effects of macro-nutrient ratios on thiamin content and transfer in phytoplankton and copepods
  • 2023
  • In: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 45:2, s. 360-371
  • Journal article (peer-reviewed)abstract
    • Vitamin B-1 (thiamin) is primarily produced by bacteria, phytoplankton and fungi in aquatic food webs and transferred to higher trophic levels by ingestion. However, much remains unknown regarding the dynamics this water-soluble, essential micronutrient; e.g. how it relates to macronutrients (carbon, nitrogen and phosphorous). Nutrient limitation has been found to be related to periods of thiamin deficiency as well as in models. Hence, thiamin transfer to copepods from three phytoplankton species from different taxa was investigated, along with the effect of various nutrient regimes on thiamin content. Nutrient levels did not affect thiamin content of phytoplankton nor the transfer to copepods. Instead, phytoplankton displayed species-specific thiamin and macronutrient contents and whilst a higher thiamin content in the prey lead to higher levels in copepods, the transfer was lower for Skeletonema compared to Dunaliella and Rhodomonas. In all, thiamin transfer to copepods is not only dependent on thiamin content of the prey, but also the edibility and/or digestibility is of importance. Thiamin is essential for all organisms, and this study offers insights into the limited effect of macronutrients on the dynamics and transfer of thiamin in the aquatic food webs.
  •  
17.
  • Fridolfsson, Emil, et al. (author)
  • Species-specific content of thiamin (vitamin B1) in phytoplankton and the transfer to copepods
  • 2020
  • In: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 42:3, s. 274-285
  • Journal article (peer-reviewed)abstract
    • Thiamin (vitamin B1) is primarily produced by bacteria and phytoplankton in aquatic food webs and transferred by ingestion to higher trophic levels. However, much remains unknown regarding production, content and transfer of this water-soluble, essential micronutrient. Hence, the thiamin content of six phytoplankton species from different taxa was investigated, along with the effect of thiamin amendment on thiamin content. Furthermore, thiamin transfer to copepods was estimated in feeding experiments. Prey type, not phytoplankton thiamin content per se, was the most important factor for the transfer of thiamin, as it was lowest from filamentous Cyanophyceae and highest from more easily ingested prey like Dunaliella tertiolecta and Rhodomonas salina. Cyanophyceae had the highest thiamin content of the investigated species, eightfold higher than the lowest. Phytoplankton varied in thiamin content related to the supply of thiamin, where thiamin addition enabled higher thiamin content in some species, while copepod thiamin content was less variable. In all, thiamin transfer is not only dependent on the prey thiamin content, but also the edibility and/or digestibility is of importance. Thiamin is essential for all organisms, and this study constitutes an important building block to understanding the dynamics and transfer of thiamin in the aquatic food web.
  •  
18.
  • Gambill, M., et al. (author)
  • Effects of temperature on the feeding and growth of the larvae of the invasive ctenophore Mnemiopsis leidyi
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:5, s. 1001-1005
  • Journal article (peer-reviewed)abstract
    • Carbon-specific prey clearance and ingestion rates of 1.5-mm tentaculate larvae of the ctenophore Mnemiopsis leidyi increased linearly between 6 and 25 degrees C but declined between 25 and 30 degrees C. Both absolute (length) and carbon-specific growth rate increased linearly with increasing temperature. The latter was 0.87 d(-1) at 25 degrees C. Extremely low or negative growth rates observed at 6 and 30 degrees C help define the thermal limits to population growth of this successful biological invader.
  •  
19.
  • Golz, Anna-Lea, et al. (author)
  • Stoichiometric regulation in micro- and mesozooplankton
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:2, s. 293-305
  • Journal article (peer-reviewed)abstract
    • Aquatic ecosystems experience large natural variation in elemental composition of carbon (C), nitrogen (N) and phosphorus (P), which is further enhanced by human activities. Primary producers typically reflect the nutrient ratios of their resource, whose stoichiometric composition can vary widely in conformity to environmental conditions. In contrast, C to nutrient ratios in consumers are largely constrained within a narrow range, termed homeostasis. In comparison to crustacean zooplankton, less is known about the ability of protozoan grazers and rotifer species to maintain stoichiometric balance. In this study, we used laboratory experiments with a primary producer (Nannochloropsis sp.), three different species of protozoan grazers and one mesozooplankton species: two heterotrophic dinoflagellates (Gyrodinium dominans and Oxyrrhis marina), a ciliate (Euplotes sp.) and a rotifer (Brachionus plicatilis) to test the stoichiometric response to five nutrient treatments. We showed that the dependency of zooplankton C: N: P ratios on C: nutrient ratios of their food source varies among species. Similar to the photoautotroph, the two heterotrophic dinoflagellates weakly regulated their internal stoichiometry. In contrast, the strength of stoichiometric regulation increased to strict homeostasis in both the ciliate and the rotifer, similar to crustacean zooplankton. Our study further shows that ciliate and rotifer growth can be constrained by imbalanced resource supply. It also indicates that these key primary consumers have the potential to trophically upgrade poor stoichiometric autotrophic food quality for higher trophic levels.
  •  
20.
  • Gorokhova, Elena (author)
  • Individual body size as a predictor of lipid storage in Baltic Sea zooplankton
  • 2019
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 41:3, s. 273-280
  • Journal article (peer-reviewed)abstract
    • The size structure of a zooplankton community is frequently used as a trait reflecting functional properties, including biochemical composition. Therefore, a shift in zooplankton body size can reflect shifts in the nutritional quality of zooplankton. In dominant Baltic copepods and cladocerans, neutral to polar lipid ratio (NL/PL ratio), a proxy for the mass-normalized lipid storage, was determined and related to individual body weight. A significant relationship between the NL/PL ratio and body weight was found; the latter was the strongest and the most significant predictor of the lipid storage capacity across different species and developmental stages. These findings provide support for using mean body weight in zooplankton community as a proxy for lipid storage capacity of zooplankton prey and justify applicability of zooplankton mean size as an indicator of nutritional conditions for Baltic zooplanktivores.
  •  
21.
  • Gorokhova, Elena, et al. (author)
  • Toxin concentration in Nodularia spumigena is modulated by mesozooplankton grazers
  • 2009
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 31:10, s. 1235-1247
  • Journal article (peer-reviewed)abstract
    • The ecological role of nodularin in cyanobacterium Nodularia spumigena is still largely unknown, as are the conditions that promote toxin production. We report a modulating effect of mesozooplankton grazing on cellular nodularin content in N. spumigena expressed as a decrease in cell-bound toxin concentration in the presence of copepods compared with the cyanobacterium in similar assemblages without copepods. In our experiments, N. spumigena was incubated in an ambient plankton (< 90 mu m) assemblage (Expt I) or in 0.2-mu m filtered seawater (Expt II), with and without the copepod Eurytemora affinis. Following similar to 28-h incubation, we measured the changes in N. spumigena abundance and nodularin concentration, frequency of Nodularia DNA occurrence in copepods as a proxy for grazing pressure on the cyanobacterium and individual RNA content in E. affinis as a proxy for copepod growth response. In all copepod-free treatments, intracellular nodularin concentrations were up to four times higher than in the treatments containing copepods. In Experiment I, the copepods also has a positive effect on the cyanobacterium growth, presumably due to a selective removal of more edible algal species and thus decreased competition for nutrients. Nodularia DNA was detected with high frequencies, 18-80%, increase in treatments with no alternative food or high copepod densities. Simultaneously, no noxious effects of N. spumigena on the copepods were detected as indicated by higher RNA content in copepods exposed to N. spumigena with or without ambient plankton organisms compared with started controls. These findings stress the need to understand the importance of intra-specific interactions for nodularin production in relation to population dynamics of N. spumigena.
  •  
22.
  •  
23.
  • Granhag, Lena, 1974, et al. (author)
  • Size-specific clearance rates of the ctenophore Mnemiopsis leidyi based on in situ gut content analyses
  • 2011
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:7, s. 1043-1052
  • Journal article (peer-reviewed)abstract
    • The ctenophore Mnemiopsis leidyi can consume large amounts of zooplankton prey.However, quantitative measurements of feeding rates, based on field data, arescarce. We measured the time required by the invasive M. leidyi to digest naturallyoccurring prey species in the Gullmar fjord, Sweden. Digestion times were relatedto prey size and type, number of prey in the gut and size of the predator. Largeprey species or many prey in the gut resulted in longer digestion times comparedwith small or few prey, but digestion time also varied with the size of M. leidyi. Theprey- and predator-specific digestion times were used together with in situ preyconcentrations and gut contents of M. leidyi to calculate the clearance rates.Clearance rate as a function of ctenophore size is presented for the most abundantmesozooplankton: Acartia sp., Oithona sp., Oikopleura dioica and Penilia avirostris. Onthe basis of the relation between digestion time and the carbon content ratiobetween prey and predator, we discuss the possible effects of mixed prey assemblageson the estimates of clearance rates.
  •  
24.
  • Hagström, Johannes, et al. (author)
  • Domoic acid production and elemental composition of two Pseudo-nitzschia multiseries strains, from the NW and SW Atlantic Ocean, growing in phosphorus- or nitrogen-limited chemostat cultures.
  • 2011
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:2, s. 297-308
  • Journal article (peer-reviewed)abstract
    • Here we compare cell physiology and domoic acid (DA) production for two strains of the diatom Pseudo-nitzschia multiseries originating from two opposite latitudes: Canada (CA) and Brazil (BR). The algae were grown as chemostat cultures at 0.2, 0.3 and 0.4 day−1 under nitrogen (N)- and phosphorus (P)-deficient conditions. The level of deficiency significantly affected the atomic C:N, C:P, C:Si and N:P ratios in both strains. In both strains, P per cell was 2–4× higher in the N- than in the P-deficient cultures. The opposite was not found for N in the P-deficient cultures, as shown by the N:P ratios and C:N ratios. The C:N and C:P ratios were significantly lower in the CA strain, and this did not change due to the level of deficiency. The concentration and production of DA per cell per day were significantly higher for both strains under P deficiency as expected since the toxin is rich in N. However, DA was also produced by both strains during continuous cell division under N deficiency. High or low bacterial densities associated with P. multiseries did not increase or decrease DA production. Our data imply that more attention needs to be given to the N:P ratios and concentrations in the waters where these algae occur, as both N and P deficiencies affect DA production and cellular DA concentrations.
  •  
25.
  • Hampton, SE, et al. (author)
  • Environmentally controlled Daphnia spring increase with implications for sockeye salmon fry in Lake Washington, USA
  • 2006
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 28:4, s. 399-406
  • Journal article (peer-reviewed)abstract
    • In Lake Washington, juvenile sockeye salmon (Oncorhynchus nerka) strongly prefer Daphnia over other prey, switching uniformly to Daphnia when the threshold abundance of 0.4 Daphnia L-1 is achieved. Using long-term Lake Washington data (1978-2001) and fry trap data (1992-2001) from a major tributary, we examined the following: (i) factors that predict Daphnia pulicaria and Daphnia thorata increase to this threshold "switching" abundance, (ii) trends in Daphnia dynamics that may affect sockeye foraging and (iii) temporal correspondence of Daphnia increase and fry arrival. The winter abundance of D. pulicaria, in combination with basic parameters of spring conditions, was an important predictor of the date of D. pulicaria spring increase, indicating greater reliance on pelagic population dynamics (versus diapause hatch) than D. thorata exhibited. In addition, D. pulicaria was a more consistent prey than D. thorata, the latter exhibiting larger population fluctuations. Thus, recently increasing D. thorata prominence could decrease diet consistency for sockeye fry. Additionally, the timing of sockeye arrival to Lake Washington and Daphnia's increase to the switching threshold has become less concordant, so that fry in recent years have had to rely upon less profitable prey for longer periods. Long-term trends and species-specific differences in Daphnia phenology may affect fry through altering diet composition, with additional implications for other zooplankton withstanding greater predation pressure in Daphnia's absence. Recent decades of warming in Lake Washington are consistent with the warming of lakes worldwide, and complex phenological responses such as those reported here may be common as the climate continues to change.
  •  
26.
  •  
27.
  • Hansen, Benni W., et al. (author)
  • In situ and experimental evidence for effects of elevated pH on protistan and metazoan grazers
  • 2019
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 41:3, s. 257-271
  • Journal article (peer-reviewed)abstract
    • Plankton succession was studied in a hyper-eutrophic stratified estuary, Mariager Fjord, Denmark. Above the pycnocline (15 m) pH increased from 8.5 to 9.2 and the oxygen increased to super saturation after 5 d of sunny weather due to high primary production. The protistan grazers were dominated by heterotrophic dinoflagellates and mixotrophic and heterotrophic ciliates. Metazooplankton was dominated by meroplankton, rotifers and the copepod, Acartia tonsa, all with a relatively low biomass. Cirriped nauplii occupied the upper strata while polychaete larvae populated the whole water column. Bivalve larvae occurred occasionally above the pycnocline even at very high pH. In pH challenge experiments, the mixotrophic ciliate Mesodinium rubrum was the least pH tolerant species, followed by Strombidium spp., which did not cope well with seawater pH > 8.5. Some heterotrophic dinoflagellates were more tolerant with net growth at pH > 9. The predominant rotifer Synchaeta sp. tolerated up to pH 9.5 and the copepod survived pH 10 but stopped producing eggs at pH 9.5 with unaffected egg hatching success. The polychaete and cirriped larvae tolerated pH 9.5, but bivalve larvae showed decreased survival already at pH 8.5. In situ distribution patterns and pH challenge experiments suggest that pH indeed contribute to structuring zooplankton distribution.
  •  
28.
  • Heuschele, J., et al. (author)
  • The chemical ecology of copepods
  • 2014
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 36:4, s. 895-913
  • Research review (peer-reviewed)abstract
    • An increasing number of studies show the importance of chemical interactions in the aquatic environment. Our understanding of the role of chemical cues and signals in larger crustaceans has advanced in the last decades. However, for copepods, the most abundant metazoan zooplankton and essential for the functioning of the marine food web, much is still unknown. We synthesize current knowledge about chemical ecology of copepods including foraging, survival and reproduction. We also compile information on the sensory apparatus and new analytical approaches that may facilitate the identification of signal molecules. The review illustrates the importance of chemical interactions in many aspects of copepod ecology and identifies gaps in our knowledge, such as the lack of identified infochemicals and electrophysiological studies to confirm the function of sensory structures. We suggest approaches that are likely to further our understanding of the role of chemical interactions in the pelagic ecosystem.
  •  
29.
  • Hogfors, Hedvig, 1980-, et al. (author)
  • Does female RNA content reflect viable egg production in copepods? : A test with the Baltic copepod Acartia tonsa
  • 2011
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:9, s. 1460-1463
  • Journal article (peer-reviewed)abstract
    • Biomarkers are very useful for in situ assessments of zooplankton growth. In particular, RNA-based methods have been developed to estimate egg production in copepods. However, RNA-growth relationships can potentially depend on a variety of factors, such as egg quality. This study shows that in Acartia tonsa, female RNA-content reflects egg production irrespective of egg viability, implying that this growth proxy is not applicable for recruitment studies if the proportion of viable eggs fluctuates widely.
  •  
30.
  • Holeton, Claire, et al. (author)
  • Decreased astaxanthin at high feeding rates in the calanoid copepod Acartia bifilosa
  • 2009
  • In: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 31:6, s. 661-668
  • Journal article (peer-reviewed)abstract
    • In marine food webs, copepods are the major producers of a carotenoid pigment astaxanthin, which is an important antioxidant. The availability of astaxanthin for higher trophic levels can be affected by changes in phytoplankton stocks and copepod feeding; however, the functional relationship between food availability and astaxanthin production is poorly understood. We hypothesized that with a given food type and quality, astaxanthin content in copepods is positively related to feeding and egg production rates. The hypothesis was tested by measuring astaxanthin accumulation in concert with ingestion and egg production rates in the copepod Acartia bifilosa exposed to different algal concentrations (Tetraselmis suecica; 0 to 1200 mu g C L(-1)). Egg production and ingestion rates increased with increasing food availability and reached a plateau at >= 400-600 mu g C L(-1). In contrast, increasing accumulation of astaxanthin with increasing food availability was observed only at concentrations <= 150 mu g C L(-1). Contrary to our hypothesis, at 600-1200 mu g C L(-1) copepods had maximal ingestion and egg production rates, but low astaxanthin contents. It is suggested that this low accumulation of astaxanthin at high food concentrations results from a food-dependant decrease in assimilation efficiency. These findings are important for the understanding of astaxanthin dynamics within marine food webs, where increases in phytoplankton biomass may translate to a trade-off between zooplankton quantity and its nutritional quality for zooplanktivores.
  •  
31.
  • Holliland, Per B., et al. (author)
  • Assessing diet of the non-indigenous predatory cladoceran Cercopagis pengoi using stable isotopes
  • 2012
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 34:5, s. 376-387
  • Journal article (peer-reviewed)abstract
    • In the Baltic Sea, the predatory cladoceran Cercopagis pengoi is a non-indigenous species that has potential to compete for mesozooplankton with pelagic zooplanktivorous fish. To understand the extent of diet overlap with these fishes in a coastal area of the northern Baltic proper, we studied the feeding of C. pengoi using stable C-13 and N-15 isotope signatures of the predator and possible prey. Feasible combinations of sources were estimated in two ways: (i) with the IsoSource mixing model, and (ii) temporal-tracking analysis. Further, contribution of different prey was related to ambient zooplankton composition to gauge selectivity. The modelling results indicate that C. pengoi is an opportunistic generalist predator with a positive selection towards older copepodites (CIVVI) of Acartia spp. and Eurytemora affinis, which also have the greatest contribution to its diet. Positive selection towards podonid Cladocera is also likely. In contrast, evidence for extensive feeding on microzooplankton was inconclusive, and bosminids were not found to be an important prey in the zooplankton assemblages studied. As the derived diet of C. pengoi overlaps greatly with that of zooplanktivorous fish, food competition between these zooplanktivores is possible.
  •  
32.
  • Holliland, Per B., et al. (author)
  • Ontogenetic and seasonal changes in diel vertical migration amplitude of the calanoid copepods Eurytemora affinis and Acartia spp. in a coastal area of the northern Baltic Proper
  • 2012
  • In: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 34:4, s. 298-307
  • Journal article (peer-reviewed)abstract
    • We studied diel vertical migration (DVM) of the six copepodite stages of two of the most abundant crustacean zooplankton in the Baltic Sea, the calanoid copepods Eurytemora affinis and Acartia spp. The study was conducted monthly from May through October in a bay in the northwestern Baltic proper. Fish biomass, phytoplankton abundance and temperature were obtained in conjunction with the zooplankton sampling. Both copepod species performed DVM. With the exception of females, all E. affinis copepodite stages performed migrations of over 10 m with only a slight increase with the copepodite stage. Adult female E. affinis remained at depth with only slight upward movement at night. In Acartia spp., DVM amplitude increased with stage and size, suggesting an ontogenetic shift in behaviour; although they had a less pronounced DVM than E. affinis. Although DVM amplitude increased with size, indicative of visual predation, fish biomass did not correlate with the amplitude of DVM. However, fish were present throughout the study period. We surmise that these ontogenetic shifts in behaviour are due to size increase and therefore visibility to predators and that the difference in DVM between the species may well be a result of physiological differences and reproductive strategy.
  •  
33.
  • Holmborn, Towe, 1979-, et al. (author)
  • Genetic species identification and low genetic diversity in Pseudocalanus acuspes of the Baltic Sea
  • 2011
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:3, s. 507-515
  • Journal article (peer-reviewed)abstract
    • Calanoid copepods of the genus Pseudocalanus are key species in temperate-boreal marine pelagic ecosystems. Pseudocalanus species are difficult to distinguish morphologically and there is uncertainty regarding the species present in the Baltic Sea. In this study, we investigated the species composition of Pseudocalanus in the Baltic proper and the Gulf of Finland using a restriction fragment length polymorphism approach. Screening of 888 individuals from 13 different stations, sampled during various seasons on a total of 22 different occasions stretching from November 2006 until July 2008, confirmed that P. acuspes is the only Pseudocalanus species normally present in the Baltic Sea. Mitochondrial diversity is exceptionally low in Baltic Sea populations of P. acuspes, as only two cytochrome oxidase I haplotypes were observed in samples ranging from the Gulf of Finland in the north to the Arkona Basin in the south (83 individuals). This unusually low level of genetic diversity indicates that planktonic organisms may experience loss of genetic diversity in marginal Baltic Sea populations, despite large population sizes. Low genetic diversity may negatively impact the species' capacity for adaptation to environmental change.
  •  
34.
  • Hosia, Aino, et al. (author)
  • Autumnal bottom-up and top-down impacts of Cyanea capillata: a mesocosm study
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:5, s. 1042-1055
  • Journal article (peer-reviewed)abstract
    • Jellyfish are effective predators on mesozooplankton and release large amounts of dissolved organic matter. Nevertheless, jellyfish initiated trophic cascades and bottom-up influences impacting lower trophic levels have received limited attention. We conducted a mesocosm experiment to quantify simultaneous top-down and bottom-up effects of a common jellyfish, Cyanea capillata, in a natural plankton community during autumn. Treatments were 0, 2 or 5 jellyfish per 2.5 m3 mesocosm, four replicates each, with initial additions of inorganic nutrients. Primary and bacterial production, species abundance and composition of several trophic levels and nutrient and carbon dynamics were followed during the 8-day experiment. Multivariate statistics and generalized additive mixed modelling were applied to test whether jellyfish carbon concentration (0–1.26 mg jellyC L−1) in the mesocosms affected the variables monitored. Unexpected negligible predatory impact of jellyfish on mesozooplankton was observed, potentially related to jellyfish senescence. Community compositions of bacteria, phytoplankton and mesozooplankton changed with time, but did not differ between treatments. However, nutrient regeneration by jellyfish was evident, and jellyfish had a positive impact on total and specific bacterial production, total primary production and the >10 µm chlorophyll a fraction. Bottom-up influences from abundant jellyfish could thus stimulate productivity in nutrient depleted autumnal surface waters.
  •  
35.
  •  
36.
  • Hosia, A., et al. (author)
  • Seasonal abundance and vertical distribution of siphonophores in western Norwegian fjords
  • 2008
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 30:8, s. 951-962
  • Journal article (peer-reviewed)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.
  •  
37.
  •  
38.
  • Hylander, Samuel, et al. (author)
  • Climate-induced input of turbid glacial meltwater affects vertical distribution and community composition of phyto- and zooplankton
  • 2011
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 33:8, s. 1239-1248
  • Journal article (peer-reviewed)abstract
    • Receding glaciers are among the most obvious changes caused by global warming, and glacial meltwater entering lakes generally forms plumes of particles. By taking vertical samples along a horizontal gradient from such a particle source, we found that photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) attenuated 20-25% faster close to the inflow of suspended particles compared with the more transparent part of the gradient. All sampled stations had a deep chlorophyll a (Chl a) maximum at 15-20 m which was more distinct in the transparent part of the horizontal gradient. Picocyanobacteria increased in abundance in more transparent water and their numbers were tightly correlated with the intensity of the deep Chl a maxima. Motile species of phytoplankton had a deeper depth distribution in transparent versus less transparent water. Yet other species, like Chrysochromulina parva, that can withstand high PAR intensities and low nutrient concentrations, increased in abundance as the water became more transparent. Also copepods increased in abundance, indicating that they are more successful in transparent water. We conclude that sediment input into lakes creates horizontal gradients in PAR and UVR attenuation which strongly affect both distribution and behavior of phyto-and zooplankton. The input of glacial flour creates a sub-habitat that can function as a refuge for species that are sensitive to high PAR and UVR exposure. When the glacier has vanished, this habitat may disappear. During the melting period, with heavy sediment input, we predict that competitive species in transparent waters, like Chrysocromulina, picocyanobacteria and copepods, will become less common. The deep Chl a maxima is also likely to become less developed. Hence, glacier melting will probably have profound effects on both species composition and behavior of several planktonic taxa with potential effects on the food web.
  •  
39.
  • Hylander, Samuel, et al. (author)
  • Vertical migration mitigates UV effects on zooplankton community composition
  • 2010
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 32:7, s. 971-980
  • Journal article (peer-reviewed)abstract
    • Several zooplankton species are susceptible to ultraviolet radiation (UV), suggesting that UV may shape zooplankton community composition. Little is known, however, about the quantitative effects of long-term UV exposure in relation to biological processes. Therefore, we studied effects of UV on behaviour, population dynamics and reproduction of several zooplankton taxa. We identified different strategies regarding daytime vertical distribution: a strong response to UV threat, illustrated by Daphnia; a weak, albeit significant response, such as in copepods; and lastly, a stationary position in a depth refuge, as in Chydorus and Eurycercus. The relative abundances of the different zooplankton species were similar and only Daphnia and copepod nauplii displayed a slight decrease in relative abundance in response to UV treatment. Daphnia also reacted to the UV threat by increasing resting egg production, whereas long-term population dynamics for all studied species were surprisingly similar between treatments, despite considerable differences in UV exposure for several months. We conclude that zooplankton communities at temperate latitudes are able to survive increased UV levels due to efficient defences, suggesting that future potential increases in UV radiation may result in only moderate impacts on zooplankton population dynamics and community composition.
  •  
40.
  • Isaksson, Anneli, et al. (author)
  • Bacterial grazing by phagotrophic phytoflagellates in a deep humic lake in northern Sweden
  • 1999
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 21:2, s. 247-268
  • Journal article (peer-reviewed)abstract
    • Bacterial grazing was measured from June to August 1995 in Lake Örträsket, a deep brown-water lake in northern Sweden. Mixotrophic chrysophytes were the dominating bacterivores at all times, grazing 3-14% of bacterial standing stock daily. The effects of altered nutrient supply and light availability on grazing activity and growth were studied in two mesocosm experiments. Incubation in the dark did not stimulate phagotrophy, which would otherwise be expected if bacteria were mainly being used as an energy source. Furthermore, clearance rates were not reduced after alleviation of nutrient limitation conditions. Rather, phagotrophy may work as a relatively fixed attribute of the mixotrophic community in this lake. When availability of dissolved nutrients is restricted, phagotrophy permits the mixotrophs to outcompete other phytoplankton, but they become less competitive at high nutrient concentrations. The relative share of mixotrophs in relation to total phytoplankton decreased considerably after enrichment with nitrogen + phosphorus.
  •  
41.
  • Jaspers, C., et al. (author)
  • Reproduction rates under variable food conditions and starvation in Mnemiopsis leidyi: significance for the invasion success of a ctenophore
  • 2015
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 37:5, s. 1011-1018
  • Journal article (peer-reviewed)abstract
    • The ctenophore Mnemiopsis leidyi is characterized by high growth rates and a large reproductive capacity. However, reproductive dynamics are not yet well understood. Here, we present laboratory data on food-dependent egg production in M. leidyi and egg hatching time and success. Further, we report on the reproduction of laboratory-reared and field-caught animals during starvation. Our results show that the half-saturation zooplankton prey concentration for egg production is reached at food levels of 12-23 mu gC L-1, which is below the average summer food concentration encountered in invaded areas of northern Europe. Furthermore, starved animals continue to produce eggs for up to 12 days after cessation of feeding with high overall hatching success of 65-90%. These life history traits allow M. leidyi to thrive and reproduce in environments with varying food conditions and give it a competitive advantage under unfavourable conditions. This may explain why recurrent population blooms are observed and sustained in localized areas in invaded northern Europe, where water exchange is limited and zooplankton food resources are quickly depleted by M. leidyi. We suggest that these reproductive life history traits are key to its invasion success.
  •  
42.
  • Jaspers, Cornelia, et al. (author)
  • Seasonal dynamics of early life stages of invasive and native ctenophores give clues to invasion and bloom potential in the Baltic Sea
  • 2013
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 35:3, s. 582-594
  • Journal article (peer-reviewed)abstract
    • Recently, both the invasive ctenophore Mnemiopsis leidyi and the arctic Mertensia ovum were discovered in the Baltic Sea but their range expansion remains unclear due to misidentification of their larval stages. Supported by molecular species verification we describe seasonal abundance and distribution of larvae and eggs of these two species. We show that their occurrence is significantly but inversely related to salinity. Mertensia ovum was present year round throughout the brackish Baltic Sea but also occurred in high-saline areas during cold seasons. Larvae of M. leidyi occurred throughout all seasons in high-saline areas but never extended further into the central Baltic. Highest ctenophore egg abundances were observed in high-saline areas during summer along with the first appearance of M. leidyi adults. The M. leidyi population peaked 2 months after the first occurrence of adults in high-saline areas, suggesting these areas as a source for lower saline regions. Low larvae abundances and a reduced transitional-to-adult ratio in the southern Baltic point to reduced or no active recruitment, suggesting that drift of animals from high-saline into lower saline regions sustains the M. leidyi population in the southern Baltic such as the Arkona and Bornholm basins.
  •  
43.
  • Jephson, Therese, et al. (author)
  • Species- and stratification-dependent diel vertical migration behaviour of three dinoflagellate species in a laboratory study
  • 2009
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 31:11, s. 1353-1362
  • Journal article (peer-reviewed)abstract
    • This study shows that different species of the same genus can behave differently in relation to a salinity gradient and suggests that a halocline can act as a barrier to the diel vertical migration (DVM) of dinoflagellate species. In a laboratory study, we found that the dinoflagellates Ceratium furca, C. tripos and Dinophysis acuta did not cross a salinity gradient of 5 psu, but instead exhibited DVM exclusively below and above the halocline. Furthermore, C. tripos aggregated in the halocline during the night and migrated to the surface at midday, whereas C. furca aggregated in the halocline at midday and migrated downwards to the bottom during the dark period. Dinophysis acuta was found exclusively above the halocline, with the highest density in the surface water at midday. The present results suggest that different dinoflagellate species display unique DVM behaviours in stratified waters. The species-specific DVM strategies revealed in this study are of central importance for understanding the ecology of these taxa and to further elucidate both the ecological significance and the mechanisms of DVM.
  •  
44.
  •  
45.
  • Karlsson-Elfgren, Irene, et al. (author)
  • Pelagic growth and colony division of Gloeotrichia echinulata in Lake Erken
  • 2005
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:2, s. 145-151
  • Journal article (peer-reviewed)abstract
    • Gloeotrichia echinulata colony development was monitored in Lake Erken, Sweden and studied inenclosure experiments. Significant colonial division did not occur in mesh bags, although the abundance ofthe pelagic population in the lake increased during the experimental periods. On the basis of these findings,it is suggested that circulation of G. echinulata to deeper nutrient rich water supports pelagic growth. Insupport of this, a large part of the buoyant G. echinulata colonies in Lake Erken was found at severalmeters depth. In an experiment with nutrient additions, the only treatment that favoured G. echinulatadevelopment was additions of phosphate, nitrate and iron. Trace element additions had a negative effecton the development of G. echinulata. On the basis of these findings, the nutritional requirements ofG. echinulata are discussed.
  •  
46.
  • Klevjer, Thor A., et al. (author)
  • In situ behaviour and acoustic properties of the deep living jellyfish Periphylla periphylla
  • 2009
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 31:8, s. 793-803
  • Journal article (peer-reviewed)abstract
    • The importance of jellyfish in marine systems is increasingly being recognized, and in some ecosystems, jellyfish may now be considered the top predator. We studied the behaviour of individuals of the deep-water schypozoan Periphylla periphylla in one such location, the Lurefjord, Norway. The study was performed using a combination of submersible acoustics (38 kHz), video and net methods, and the focus was on variation in behaviour and vertical distribution in relation to the diel cycle. A proportion of the population underwent synchronous vertical migrations, but P. periphylla were still recorded throughout the water column both day and night. The majority of individuals were swimming (vertically) at speeds < 2 cm s(-1) irrespective of the time of day. However, occasional vertical swimming events with speeds exceeding 10 cm s(-1) were recorded. Such events of elevated vertical speeds were of short duration, followed by subsequent periods of no vertical movements. Different size fractions appeared to have different patterns of vertical swimming activity, with smaller jellyfish swimming more continuously than the larger Periphylla. The echo strengths of the individual returns (target strength, TS) peaked at approximately -62 dB, and variability in TS for individuals was high, with the strongest echoes seen in deep water. The results show the feasibility of acoustic methods for studying the in situ behaviour and acoustic properties of these jellyfish, but also that acoustically weak jellyfish are only recorded close to the transducer or the acoustic axis, which will bias acoustic data on vertical size distribution and acoustic abundance estimates.
  •  
47.
  • Lischke, Betty, et al. (author)
  • Large biomass of small feeders : Ciliates may dominate herbivory in eutrophic lakes
  • 2016
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 38:1, s. 2-15
  • Journal article (peer-reviewed)abstract
    • The importance of ciliates as herbivores and in biogeochemical cycles is increasingly recognized. An opportunity to observe the potential consequences of zooplankton dominated by ciliates arose when winter fish kills resulted in strong suppression of crustaceans by young planktivorous fish in two shallow lakes. On an annual average, ciliates made up 38-76% of the total zooplankton biomass in both lakes during two subsequent years. Consequently, ciliate biomass and their estimated grazing potential were extremely high compared with other lakes of various trophic states and depths. Grazing estimates based on abundance and size suggest that ciliates should have cleared the water column of small (<5 mu m) and intermediate (5-50 mu m) sized phytoplankton more than once a day. Especially, small feeders within the ciliates were important, likely exerting a strong top-down control on small phytoplankton. Particle-attached bacteria were presumably strongly suppressed by intermediate-sized ciliate feeders. In contrast to other lakes, large phytoplankton was proportionately very abundant. The phytoplankton community had a high evenness, which may be attributed to the feeding by numerous fast growing and selective ciliate species. Our study highlights ciliates as an important trophic link and adds to the growing awareness of the role of winter processes for plankton dynamics.
  •  
48.
  • Majaneva, Sanna, et al. (author)
  • Feeding of the Arctic ctenophore Mertensia ovum in the Baltic Sea : evidence of the use of microbial prey
  • 2014
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 36:1, s. 91-103
  • Journal article (peer-reviewed)abstract
    • Since its first reported appearance in the Baltic Sea in 2007, there has been a little research on the role of the Arctic ctenophore Mertensia ovum in this ecosystem. We provide results from the first feeding experiments of M. ovum from the northern Baltic Sea. Experiments were conducted with various prey types; picocyanobacteria Synechococcus bacillaris, ciliates Mesodinium rubrum, nauplii of mixed copepod species and copepodites of Eurytemora affinis. Molecular gut content analyses were also used to measure in situ feeding of M. ovum on the picocyanobacteria. The observed clearance rates on M. rubrum (< 9.0 mL predator(-1) h(-1)), and S. bacillaris (<7.5 mL predator(-1) h(-1)) were lower than those reported for similar-sized ctenophore species feeding on similar prey. Similarly, clearance rates of M. ovum on copepodites and copepod nauplii were close to zero, implying significantly lower predation on crustacean prey compared with other ctenophores. Overall, M. ovum predation rates were relatively low with a maximum daily consumption of 0.95 mu g C ind.(-1) day(-1) (similar to 15.8% of estimated predator carbon content). In addition, we examined the vertical distribution of M. ovum in relation to that of micro- and mesozooplankton and found greater overlap with potential microplankton prey than with mesozooplankton. Taken together, these results imply that in the Baltic Sea, M. ovum feed mainly on bacterio-and microplankton, thus potentially contributing to the coupling between the microbial loop and higher consumers in the pelagic food web.
  •  
49.
  • Ogonowski, Martin, 1980-, et al. (author)
  • A weight and temperature dependent model of respiration in Praunus flexuosus (Crustacea, Mysidacea)
  • 2012
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 34:7, s. 642-645
  • Journal article (peer-reviewed)abstract
    • The mysid shrimp Praunus flexuosus is common in littoral habitats in the Baltic Sea and other marine areas, but its bioenergetic characteristics have not been studied. We present the first model of its routine respiration rate as a function of size and a natural temperature range. The model explained 87% of the variance in respiration, indicating that it could be useful in a larger modeling framework. Specific respiration rates and temperature dependence were consistent with previous reports for this and other littoral mysids at low-to-moderate temperatures. Respiration at higher temperatures was lower, indicating that previous reports may have been biased by residual SDA (specific dynamic action) effects. Increased respiration due to SDA was detectable over a longer period than previously reported, ∼30 h.
  •  
50.
  • Olivares, Manuel, et al. (author)
  • Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus
  • 2020
  • In: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 42:6, s. 742-51
  • Journal article (peer-reviewed)abstract
    • Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.
  •  
Skapa referenser, mejla, bekava och länka
  • Result 1-50 of 99
Type of publication
journal article (98)
research review (1)
Type of content
peer-reviewed (99)
Author/Editor
Rengefors, Karin (6)
Hansson, Lars-Anders (5)
Granéli, Edna (3)
Granéli, Wilhelm (3)
Hansson, Sture (3)
Riemann, Lasse (3)
show more...
Andersson, Agneta (2)
Larsson, Ulf (2)
Holliland, Per B. (2)
Carlsson, Per (2)
Bergström, Ann-krist ... (2)
Engström-Öst, Jonna (2)
Bonnet, D. (1)
Dahl, K. (1)
Michel, C. (1)
Karlsson, Magnus (1)
Andersson, A (1)
Nielsen, G (1)
Hilt, Sabine (1)
Pettersson, K (1)
Odebrecht, C (1)
Olsson, P. (1)
Berglund, J (1)
Stenlid, Jan (1)
Sommaruga, Ruben (1)
Winder, Monika (1)
Petranovic Nielsen, ... (1)
Andersson, Lars (1)
Jansson, Mats (1)
Rydin, Emil (1)
Harris, R (1)
Ahlbeck, Ida (1)
Vrede, Tobias (1)
Hyenstrand, Per (1)
Jonsson, Per R., 195 ... (1)
Berggren, Martin (1)
Jönsson, Mikael (1)
Motwani, Nisha H. (1)
Lindehoff, Elin (1)
Larsson, Ann I., 196 ... (1)
Godhe, Anna, 1967 (1)
Roland, Fábio (1)
Vehmaa, Anu (1)
Brutemark, Andreas (1)
Alonso-Saez, Laura (1)
Unanue, Marian (1)
Latatu, Ainhoa (1)
Azua, Inigo (1)
Ayo, Begona (1)
Artolozaga, Itxaso (1)
show less...
University
University of Gothenburg (27)
Uppsala University (18)
Stockholm University (17)
Lund University (15)
Umeå University (14)
Linnaeus University (13)
show more...
Chalmers University of Technology (4)
Swedish University of Agricultural Sciences (3)
Linköping University (2)
Malmö University (1)
Mid Sweden University (1)
Karlstad University (1)
show less...
Language
English (99)
Research subject (UKÄ/SCB)
Natural sciences (86)
Engineering and Technology (1)
Agricultural Sciences (1)

Year

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Close

Copy and save the link in order to return to this view