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1.
  • Weich, R G, et al. (författare)
  • Extracellular alkaline phosphatase activity in Ulva lactuca L
  • 1989
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 129:1, s. 33-44
  • Tidskriftsartikel (refereegranskat)abstract
    • Extracellular alkaline phosphatase activity (APA) was detected in the marine macroalga Ulva lactuca, cultivated in laboratory conditions under phosphate limitation. Algal discs were grown in continuous light and in darkness for a maximum of 205 h in sterilized seawater supplied with ammonium nitrate and various phosphate concentrations. APA and phosphate uptake in U. lactuca was stimulated in light whereas inhibition was detected in darkness. APA increased significantly during the cultivation in a phosphate-deficient medium but was suppressed at high external phosphate concentrations. In addition, pretreatment in penicillin over 48 h markedly enhanced enzyme activity during P limitation. The pretreatment in penicillin reduced the number of surface-associated bacteria. Our results indicate that APA in U. lactuca was dependent on the external phosphate concentration, energy from photophosphorylation and bacteria. Since intracellular polyphosphates and an orthophosphate pool still were displayed in 31P NMR spectra after cultivation at phosphate-limiting conditions, P deficiency was not suggested. Unfortunately, NMR spectra reflect total amounts of P compounds and local differences in the P status of the multicellular tissue could not be distinguished. Postulating a negative correlation between the P status and APA, a lower P status in meristematic areas during P limitation was suggested. Alkalisation of the growth medium during algal growth in light, and/or intracellular pH changes may additionally have affected enzyme production. 
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2.
  • Aljetlawi, A A, et al. (författare)
  • Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis
  • 2000
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - Umea Univ, Dept Ecol & Environm Sci, SE-90187 Umea, Sweden.. - 0022-0981 .- 1879-1697. ; 249:2, s. 263-280
  • Tidskriftsartikel (refereegranskat)abstract
    • We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1 +) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay. (C) 2000 Elsevier Science BN: All rights reserved.
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3.
  • Granéli, Edna, et al. (författare)
  • Effects of river water of different origin on the growth of marine dinoflagellates and diatoms in laboratory cultures
  • 1990
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981 .- 1879-1697. ; 136:2, s. 89-106
  • Tidskriftsartikel (refereegranskat)abstract
    • The hypothesis that acid humic-rich river water selectively favours dinoflagellates in comparison to diatoms in coastal waters was tested in two sets of laboratory experiments using unialgal cultures of marine phytoplankton. In the first experiment, three dinoflagellates, i.e., Prorocentrum minimum (Pav.) J. Schiller, P. micans Ehrenberg and Amphidinium carterae Hulburt, and three diatoms, i.e., Attheya decora T. West, Skeletonema costatum (Grev.) Cleve and Phaeodactylum tricornutum Bohlin, were grown in a mixture of 80% coastal (S 20%.) and 20% river water. Water from seven different rivers was used. Four rivers had a high humic content (yellow substance 22.1 ± 0.9 · m−1) but lower inorganic N and P concentrations ("forest rivers") while three rivers ("agricultural rivers") had a lower humic content (10.7 ± 1.3 · m−1) but inorganic nutrient concentrations approximately three times as high as the forest rivers. The growth rates for the dinoflagellates were significantly higher in the medium with forest river water compared to the mixtures with agricultural river water while the opposite was true for the diatoms. In the second type of experiment, the diatom Ditylum brightwellii (T. West) Grun and the dinoflagellate P. minimum were grown, as semicontinuous dilution cultures, in mixtures of 90% coastal water (S 20%.) and 10% river water. Water from four different rivers was used, one draining mainly agricultural soils and the other acidified humic-rich forested soils. River water of agricultural origin supported a higher D. brightwellii biomass and growth rate than river water draining forested soils while for P. minimum the opposite was true. Decreasing cell P quotas and increasing alkaline phosphatase activity indicated that D. brightwellii was P-deficient, especially when agricultural river water was added, while these physiological indices suggested that P. minimum cultures were not P-starved. Our results support the hypothesis that the discharge of acidified river water, rich in humic substances, to coastal waters, can play a role in shifting the species composition from diatoms to dinoflagellates. 
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4.
  • Granéli, Edna, et al. (författare)
  • The response of planktonic and microbenthic algal assemblages to nutrient enrichment in shallow coastal waters, Southwest Sweden
  • 1985
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 85:3, s. 253-268
  • Tidskriftsartikel (refereegranskat)abstract
    • Field and laboratory nutrient (nitrogen and phosphorus) enrichment experiments were performed using natural phytoplankton and microphytobenthic assemblages from the brackish water Öresund, S.W. Sweden. The response of algae from a low-nutrient area (Falsterbo Canal) was compared to that of algae from a polluted, nutrient-rich area (Lomma Bay).The biomass (measured as chlorophyll a) of both phytoplankton and microphytobenthos from the Falsterbo Canal increased after the addition of nitrogen. Phytoplankton growth was stimulated by the addition of phosphorus to the nitrogen-rich water of the polluted Lomma Bay. Sediment chlorophyll a showed no significant increase after the addition of nutrients in the Lomma Bay. In containers without sediment, phytoplankton uptake was calculated to account for ≈ 90% of the disappearance of inorganic fixed nitrogen from the water. In the sediment containers the microphytobenthos was estimated to account for ≈20% of the nitrogen uptake. The rest was presumably lost mainly through denitrification.When containers with microphytobenthos from Lomma Bay were kept in the dark, phosphorus was released at a rate of up to ≈ 180 μM · m−2 · day−1. We suggest that by producing oxygen microbenthic algae keep the sediment surface oxygenated thereby decreasing phosphorus transport from the sediment to the overlying water. 
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5.
  • Macia, Adriano, et al. (författare)
  • Thorn fish Terapon jarbua (Forskål) predation on juvenile white shrimp Penaeus indicus H. Milne Edwards and brown shrimp Metapenaeus monoceros (Fabricius) : the effect of turbidity, prey density, substrate type and pneumatophore density
  • 2003
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981 .- 1879-1697. ; 291:1, s. 29-56
  • Tidskriftsartikel (refereegranskat)abstract
    • A series of laboratory experiments was conducted at Inhaca Island Marine Biological Station, Mozambique, in order to assess the separate effects of turbidity, prey density, substrate type, pneumatophore density, and the combined effects of turbidity with the latter three, on rate of predation by the thorn fish Terapon jarbua (Forskål, 1775) on white shrimp Penaeus indicus and brown shrimp Metapenaeus monoceros. Significant interactions between turbidity and the other three factors on shrimp predation for both prey species were detected. Regardless of prey density, increasing turbidity decreased predation on P. indicus, but not on M. monoceros, for which increasing densities reduced the protective effect of turbidity. Increasing prey density increased predation on P. indicus in clear water, and increased predation on M. monoceros in low and high, but not in intermediate turbidity or clear water. The presence of a substrate suitable for burying decreased predation on M. monoceros in clear water, but not in the turbidity levels used. In clear water, solely sandy-shell substrate afforded protection to P. indicus, while in turbid water, no substrate offered significant protection and muddy substrate even increased prey vulnerability to fish probably as a result of increased preys' locomotor activity. Raising pneumatophores density seems to lower the protective value of turbidity for both species. In clear water, only low and high structure density provided a deterrent effect on predation on P. indicus; in turbid water, intermediate and higher structure density increased predation. Increasing structural complexity reduced predation on M. monoceros linearly in clear water; but in low turbid water it increased. In high turbid waters, the increase was only significant in intermediate pneumatophore density. High structural complexities impair the pursuing capacity of fish and thus decreased predation rates. The results indicate that the effective provision of shelter of different habitats depends not only on the various environmental parameters analysed, but also on the way they interact and on the behaviour of prey and predator as well.
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6.
  • Richardson, Katherine, et al. (författare)
  • The relationship between photosynthesis measured by C-14 incorporation and by uptake of inorganic carbon in unicellular algae
  • 1984
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 81:3, s. 241-250
  • Tidskriftsartikel (refereegranskat)abstract
    • The traditional 14C method of estimating photosynthetic rates was compared with net photo-synthesis in two species of unicellular algae. Net photosynthesis was defined as the disappearance of inorganic carbon from the algal medium and was determined using a described infra-red gas analyser (IRGA) technique. For Amphidinium carterae Hulbert, the 14C method always led to lower calculated rates of photosynthesis than the IRGA technique. This difference was, on average, ≈100%. For Scenedesmusobliquus (Turpin) Kützing, the 14C method could lead to over-estimates, good agreement with, or underestimates of net photosynthesis. Although the under-estimates were only of the order of 15%, the over-estimates were in some cases > 100%. There is some indication that respiration rate is an important factor in the relationship between photosynthetic rates calculated by the two methods for this organism.
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7.
  • Sakshaug, E, et al. (författare)
  • Chemical composition and alkaline phosphatase activity of nutrient-saturated and P-deficient cells of four marine dinoflagellates
  • 1984
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 77, s. 241-254
  • Tidskriftsartikel (refereegranskat)abstract
    • Four marine dinoflagellates, Amphidinium carterae Hulburt, Ceratium tripos (O.F. Müll.) Nitzsch, Prorocentrum minimum (Pav.) J. Schiller, and Scrippsiella trochoidea (Stein) Loeblich III were grown as dilution cultures at 18°C, S = 29%. and 30 μE·m−2·s−1 at L:D = 14:10 h. In nutrient-saturated cultures, the growth rates (doubl·day−1) ranged from 0.38 for Scrippsiella to 0.80 for Prorocentrum, and carbon content (pg·cell−1) from 83 for Amphidinium to 6900 for Ceratium. The atomic N/C ratio was 0.13–0.15, but for Ceratium it was 0.088, because of its thick, cellulose theca. The atomic N/P ratio ranged from 12–13 for Ceratium and Scrippsiella to 15–17 for Prorocentrum and Amphidinium. Under P-deficient conditions (growth rate 39–70% of the maximum), cellular P decreased considerably, but so did N, so that the N/P ratio was only slightly affected. There was a concomitant increase in carbon content per cell of 1.2- to 1.7-fold. Alkaline phosphatase activity was virtually nil in nutrient-saturated cells, but was readily demonstrable in all species when P-deficient. 
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8.
  • Angeler, David (författare)
  • Effects of shrimp-farm effluents on the food web structure in subtropical coastal lagoons
  • 2011
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 402, s. 65-74
  • Tidskriftsartikel (refereegranskat)abstract
    • Although numerous studies have reported the negative effects of shrimp aquaculture on water quality, little is known about the ecological effects of these practices in coastal lagoons and near-shore marine habitats. The impact of shrimp-farm effluents on the food webs of an impacted subtropical coastal lagoon in the Gulf of California was evaluated through measurements of isotopic (delta C-13, delta N-15) signatures in sediments, plants and animals, and compared with the results of a near-pristine reference site. Degradation was manifested in a strong reduction on fish diversity at the perturbed site. delta C-13 signatures provided ambiguous evidence of degradation while delta N-15 was a better descriptor of shrimp-farm effluent impact on coastal lagoon food webs. The site receiving nutrient-rich discharges showed significant enrichment of delta N-15 (approximate to 5 parts per thousand) in sediments, macroalgae, benthic algae, filterfeeders and omnivorous feeders, resulting in qualitative differences in foodweb structure between both lagoons. The food web in the perturbed site was sustained by sediment detritus and dominated by opportunistic species. The lowest influence on delta N-15 signatures by aquaculture discharges recorded in the upper trophic levels could be explained by the shift in the composition of biotic communities, and associated feeding strategies. While alterations in resource availability do not affect directly food chain length, trophic linkages between food web compartments can be reduced as a result of shrimp farm impacts. Our study demonstrates that nutrient-enriched discharges from shrimp-farm aquaculture generate changes in the availability of food sources, which reduce biodiversity and alter structural and functional food web characteristics. (C) 2011 Elsevier B.V. All rights reserved.
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9.
  • Angove, Charlotte, et al. (författare)
  • Assessing the efficiencies and challenges for nutrient uptake by aquatic plants
  • 2018
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 507, s. 23-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Aquatic plant meadows are valuable components to the 'coastal filter' and it is important to understand the processes that drive their ability to cycle nutrients. However, at present, the field-based evidence for understanding the drivers of nutrient uptake by plants is lacking. This study aimed to investigate how well individual shoots of aquatic plants could meet their nitrogen demands using the sediment nutrient pool (porewater ammonium) and to explore which traits helped to facilitate such uptake. Several species were investigated in shallow, submerged (2-4 m) mixed-species communities in the northern Baltic Sea using incubation experiments with enriched ammonium. After a 3.5 h incubation time, individuals were collected and analysed for nitrogen (% DW) and N-15 (at-%) concentrations. Uptake by plants was calculated per unit nitrogen in response to the N-15 labelled source and to overall nitrogen availability. Background porewater ammonium availability was highly variable between individual plants. Species identity did not significantly affect uptake metrics and the effect of ambient porewater availability was weak. As biomass increased there were significant logarithmic declines in the 95th quantiles of nutrient uptake rates, ambient porewater nutrient availability and aboveground nitrogen tissue concentrations (% DW). Such findings suggested that uptake rates of plants were significantly demand driven and the nutrient conditions of the porewater were significantly driven by the demands of the plant. Findings parameterised the unfulfilled potential for some aquatic plants to cycle nutrients more efficiently and highlighted the potential importance of access to new nutrient sources as a way of enhancing nutrient cycling by aquatic plants. Plant traits and community properties such as the activity of infauna could facilitate such an access and are likely important for nutrient uptake.
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10.
  • Arroyo, Nina Larissa, et al. (författare)
  • Interactions between two closely related phytal harpacticoid copepods, asymmetric positive and negative effects
  • 2007
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 341:2, s. 219-227
  • Tidskriftsartikel (refereegranskat)abstract
    • Competition for food is generally thought to exert a strong evolutionary pressure, driving trophic niche separation, either by specialization and/or by widening the choice of potential food resources. Harpacticoid copepods are common inhabitants of phytal assemblages, where several closely related species of the so-called phytal dwelling families often co-occur. However, direct competition among phytal harpacticoids has been thought to be unlikely, due to the abundant and continuously available food supplies. We conducted a series of field and laboratory studies to assess the role of competition in the abundance distribution of two closely related harpacticoid species, Mesochra rapiens and M. aestuari. We found that the abundance of both species co-varied on several seaweed species in the northern Baltic Sea, during a 3-month period. Stable isotope ratios in the green alga Cladophora glomerata field samples indicated different resource utilization of the two species, both in fresh and deteriorated C. glomerata, and in drifting algae. We tested in the laboratory if resource utilization was different between the species in sympatry and allopatry. We used enriched stable carbon isotope ratios (C-13/C-12) of the diatom Phaeodactylum tricornutum to trace the uptake in both species. Results from these experiments showed a much higher assimilation by M. aestuari in sympatry with M. rapiens, while the latter species showed a higher assimilation in allopatry. Our results show that while there is no apparent competition for resources between these two species in the field, there seems to be an asymmetric reaction when in sympatry and provided one single resource in the laboratory. We suggest that M. rapiens may facilitate assimilation by M. acstuari and discuss the mechanisms by which this may take place.
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11.
  • Berkström, Charlotte, et al. (författare)
  • Trade-offs in the ecological versatility of juvenile wrasses : An experimental evaluation
  • 2014
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 453, s. 91-97
  • Tidskriftsartikel (refereegranskat)abstract
    • A number of theories have been advanced to explain the evolution of specialists and generalists and how they coexist. According to trade-off theory, a species can improve performance by specialising on one habitat but does so at a cost of reduced performance in others. Specialists will outperform generalists in their preferred habitats but will be outperformed by generalists in other habitats. This study aimed to examine trade-offs in juvenile coral reef wrasses that vary in their degree to which they are specialised on microhabitats. We predicted that specialists would exhibit highest survival and growth on preferred habitats, and in contrast, generalists would tend to do equally well on all habitats. Furthermore, we predicted that specialists would outperform generalists on their preferred habitat, while generalists would outperform specialists on less preferred habitats. The predictions were tested by transplanting juveniles from four different species (two specialists, and two generalists) to patch reefs constructed from different kinds of microhabitats (live coral, dead coral, and rubble) and measuring growth and survival after 3 weeks in Kimbe Bay, Papua New Guinea. Prior to this, the degree of specialisation was assessed using resource selection ratio-based field observations of habitat use and availability. Results provided mixed evidence for the trade-off hypothesis. Specialists conformed to predictions, while generalists did not. Specialist species showed higher survival rate on their preferred habitat than generalist species and the mean growth was significantly higher on the preferred habitat than less preferred habitats for one specialist species. However, generalist species did not survive on all reefs, regardless of microhabitat Growth rates between habitats could therefore not be compared for generalists and the presence of a trade-off in fitness expressed in growth may have been missed for these species. It is thus premature to reject the trade-off theory, and we encourage examining a greater range of specialist and generalist species, under conditions in which the fate of all individuals can be more accurately determined.
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12.
  • Blom, Eva-Lotta, 1973, et al. (författare)
  • Male acoustic display in the sand goby – Essential cue in female choice, but unaffected by supplemental feeding
  • 2022
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 556
  • Tidskriftsartikel (refereegranskat)abstract
    • Many teleost fishes use acoustic and visual signalling during courtship. Such displays may convey information about body condition. Here we experimentally altered body condition of sand goby (Pomatoschistus minutus) males to examine effects on acoustic and visual courtship and subsequent spawning decisions. Over two weeks, males fed in excess were fed daily, whereas food-deprived males were fed once a week. Females only spawned with males that produced courtship sound. However, there were no treatment effects on the occurrence of spawning and males fed in excess did not invest more in visual or acoustic courtship than food-deprived males. That said, males fed in excess built more well-covered nests, with more sand piled on top, compared to food-deprived males. Male condition measured as lipid content differed significantly between treatments. However, only males fed in excess differed in lipid content from wild caught males, indicating that in nature, males are of similar condition to males in the low condition treatment group. Apart from the importance of courtship sound, the only male or female behaviour predicting reproductive success was if male displayed in the nest opening. Males often produce courtship sounds together with a visual display in this position. A female dark-eye display did not associate with reproductive success which, together with previous results, suggest a non-ornamental function of this trait. We conclude that male courtship sounds appear to be crucial in female mate choice, but the information content of the courtship sounds and how it relates to male condition remains elusive.
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13.
  • Both, Adrianus, 1985-, et al. (författare)
  • Solubilization of nutritional lipids from three coastal and estuarine primary producers using sodium taurocholate as a model surfactant to mimic typical consumer gut-fluids
  • 2022
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 548
  • Tidskriftsartikel (refereegranskat)abstract
    • Coastal and estuarine food webs receive large inputs of both autochthonous and allochthonous detritus, which serves as an important dietary input for a variety of detritivorous and omnivorous organisms. Surfactants, which aid digestion by solubilizing hydrophobic lipids, are found in the gut-fluids of many fish and invertebrate consumers. To develop a biomimetic assay to explore how source of primary production and age may affect the bioavailability of nutritional lipids from detrital food sources, we assessed the capacity of a model surfactant, sodium taurocholate (STC), to solubilize fatty acids from three primary producers, a haptophyte (Isochrysis galbana), a rock-weed (Ascophyllum nodosum), and a marsh grass (Spartina alterniflora). Comparing lipids solubilized by a constant concentration of STC to traditional Folch-extracted yields, we assessed relative bioavailability of nutritional lipids from fresh and decayed material of each primary producer. We focused on the solubilization of storage triacylglycerols (TAG) and the fatty acid constituents of all lipids (FA). With a temperature of 5 °C, 28.7 mM STC solubilized 44 ± 12% of total FA from S. alterniflora and about half that fraction for I. galbana and A. nodosum after 15 h in the dark unstirred. In the form of TAG, STC solubilized 53 ± 19% of pure triolein as a reference and similar proportions from S. alterniflora (56 ± 19%) and I. galbana (48 ± 2%) but only 9 ± 3% from A. nodosum. Both approaches (TAG and FA) thus show significant differences in bioavailability among these three sources. Two months of decay had inconsistent effects on overall lipid yields but substantial effects on composition. Degradation led to decreased total phospholipids and long-chain polyunsaturated FA and increased break-down products (free FA and diacylglycerols), saturated and monounsaturated FA, and bacterial FA. Lower FA bioavailability and reduced degradation rates in A. nodosum may be due to its higher polyphenol and alginate concentrations. Although we mimicked only one component of the digestion process of lipids, this study represents a first step in developing a biomimetic assay to assess the relative bioavailability of nutritional lipids.
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14.
  • Brutemark, Andreas, et al. (författare)
  • Carbon isotope signature variability among cultured microalgae: Influence of species, nutrients and growth
  • 2009
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 372:1-2, s. 98-105
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we have investigated whether the carbon isotopic signature differs between different groups and species of marine phytoplankton depending on growth phase, nutrient conditions and salinity. The 15 investigated algal species, representing the Bacillariophyceae, Chlorophyceae, Cryptophyceae, Cyanophyceae, Dinophyceae and Haptophyceae classes were grown in batch monocultures and analysed for delta C-13 in both exponential and stationary phase. For all the cultured species, delta C-13 signatures ranged from -23.5 parts per thousand (Imantonia sp.) to - 12.3 parts per thousand (Nodulania spumigena) in the exponential phase and from - 18.8 parts per thousand (Amphidinium carterae) to - 8.0 parts per thousand (Anabaena lemmermannii) in the stationary phase. Three species (Dunaliella tertiolecta, Rhodomonas sp.. Heterocapsa triquetra) were also grown under nutrient sufficient and nitrogen or phosphorus deficient conditions. Nitrogen limitation resulted in a more negative delta C-13 signature, whereas no effect could be observed during phosphorus limitation compared to nutrient sufficient conditions. Growth of Prymnesium parvum in two different salinities resulted in a more negative delta C-13 signature in the 26 parts per thousand-media compared to growth in 7 parts per thousand-media. Our results show that the carbon isotopic signature of phytoplankton may be affected by salinity, differ among different phytoplankton species, between exponential and stationary phase, as well as between nutrient treatments. (C) 2009 Elsevier B.V. All rights reserved.
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15.
  • Carlsson, Per, et al. (författare)
  • Bacterial and phytoplankton nutrient limitation in tropical marine waters, and a coastal lake in Brazil
  • 2012
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 418, s. 37-45
  • Tidskriftsartikel (refereegranskat)abstract
    • Bioassay experiments were performed two times (with 2 years in between) in order to investigate if nitrogen (N, ammonium), phosphorus (P, phosphate) and carbon (C, glucose) additions would stimulate the growth of bacteria and phytoplankton differently in three different tropical aquatic environments. The water and their indigenous microbial communities were taken from a freshwater coastal lake (Cabiunas), a coastal (Anjos), and an offshore marine station (Sonar) in the Atlantic outside Cabo Frio, Rio de Janeiro State, Brazil. Ammonium, phosphate and glucose were added alone or in combination to triplicate bottles. In the lake, P seemed to be the primary limiting factor during the first experiment, since both bacterial production and phytoplankton growth was stimulated by the P addition. Two years later, however, addition of P inhibited phytoplankton growth. During both years, C was closely co-limiting for bacteria since CP additions increased the response considerably. For both the coastal and offshore seawater stations, phytoplankton growth was clearly stimulated by N addition in both years and the bacteria responded either to the P, N or C additions (alone or in combination). To conclude, the results from these tropical aquatic systems show that it is possible that phytoplankton and bacteria may compete for a common resource (P) in lakes, but can be limited by different inorganic nutrients in marine waters as well as lakes, suggesting that phytoplankton and bacteria do not necessarily compete for the same growth limiting nutrient in these environments. (C) 2012 Elsevier B.V. All rights reserved.
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16.
  • Carney Almroth, Bethanie, 1974, et al. (författare)
  • Warmer water temperature results in oxidative damage in an Antarctic fish, the bald notothen
  • 2015
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 468, s. 130-137
  • Tidskriftsartikel (refereegranskat)abstract
    • Global climate change is predicted to result in increases in water temperature in the polar regions, but the full consequences of this for marine fish species are not understood, especially with regard to cellular mechanisms underlying oxidative stress. Warmer temperatures could potentially result in increased oxidative stress, and it is not known whether stenothermal fish can cope with this on a cellular and physiological level. In order to address this, we exposed bald notothen (Pagothenta borchgrevinki), a fish species endemic to Antarctica, to an increase in temperature from -1.6 degrees C to 4 degrees C and measured the effects on oxidative stress including antioxidant defenses, oxidative damage in proteins and lipids, and transcriptional regulation of involved genes. We show that the fish responds to an acute (12 h) temperature increase with increased antioxidant defenses. However, these antioxidant defenses were similar to basal levels following long-term (3 weeks) exposure to the higher temperature and moreover, these individuals also had higher levels of oxidative damage. These results indicate that this species has the ability to alter levels of endogenous antioxidants, but that this response is transient and insufficient to protect against oxidative damage. These effects may have serious consequences for these fish in a warmer future since long-term consequences of this accumulation of damaged lipids and proteins are associated with aging and known to include decreased cellular function, disease and eventually cell death. (C) 2015 Elsevier B.V. All rights reserved.
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17.
  • Donadi, Serena (författare)
  • The interactive role of predation, competition and habitat conditions in structuring an intertidal bivalve population
  • 2020
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 523
  • Tidskriftsartikel (refereegranskat)abstract
    • Habitat characteristics, predation and competition are known to interactively drive population dynamics. Highly complex habitats, for example, may reduce predation and competition, allowing more individuals living together in a certain area. However, the strength and direction of such interactions can differ strongly and are context dependent. Furthermore, as habitat characteristics are rapidly changing due to anthropogenic impacts, it becomes increasingly important to understand such interactions. Here, we studied the interactive effects of predation and competition on common cockle (Cerastoderma edule) recruitment, growth and survival under different habitat characteristics in the Wadden Sea, one of the world's largest intertidal ecosystems. In a predator-exclosure experiment, we manipulated cockle densities (100 vs. 1000 individuals m(-2)) and shorebird predation at two sites differing in habitat characteristics, namely at the wake of a blue mussel bed (Mytilus edulis) and at an adjacent sandy site. We found that recruitment was higher in the mussel-modified habitat, most likely due to reduction of hydrodynamic stress. Although bird predation strongly reduced recruit density, the combined effects still yielded more recruitment at the vicinity of the mussel bed compared to the sandy area. Furthermore, we found that high cockle densities combined with high densities of other potential prey (i.e. mussels) at the mussel-modified site, mitigated predation effects for adult cockles. Apart from these positive effects on adults, mussel-modified habitat reduced cockle growth, most likely by reducing hydrodynamics in the wake of the mussel bed and by increasing inter-specific competition for food. Our study experimentally underpins the importance of habitat characteristics, competition and predation in interactively structuring intertidal communities.
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18.
  • Eggertsen, Maria, et al. (författare)
  • Coral-macroalgal interactions : Herbivory and substrate type influence growth of the macroalgae Eucheuma denticulatum (N.L. Burman) Collins & Hervey, 1917 on a tropical coral reef
  • 2021
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 542
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduced macroalgae becoming invasive may alter ecological functions and habitats in recipient ecosystems. In the Western Indian Ocean (WIO), non-native strains of the native macroalgae Eucheuma denticulatum were introduced for farming practices and consequently spread into the surrounding seascape. We investigated potential effects of non-native and native strains of this macroalgae on a branching coral. We conducted a four-factor field experiment where we examined growth and holdfast development of introduced and native E. denticulatum on live and dead branches of Acropora sp. in the presence and absence of herbivores in Unguja Island, Zanzibar. Moreover, we estimated coral and macroalgae condition by visual examinations, gene expression analyses, and photosynthetic measurements. Macroalgae did not attach to any live coral and coral condition was not impacted by the presence of E. denticulatum, regardless of geographical origin. Instead, necrotic tissue on the macroalgae in areas of direct contact with corals indicated damage inflicted by the coral. The biomass of E. denticulatum did not differ between the replicates attached to live or dead corals in the experiment, yet biomass was strongly influenced by herbivory and replicates without protection from herbivores had a significantly lower biomass. In the absence of herbivory, introduced E. denticulatum had significantly higher growth rates than native algae based on wet weight measurements. These results contribute to an increased understanding of environmental effects by the farming of a non-native strain of algae on corals and stresses the importance to maintain viable populations of macroalgal feeding fishes in such areas.
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19.
  • Engstedt, Olof, 1980-, et al. (författare)
  • Strontium (Sr) uptake from water and food in otoliths of juvenile pike (Esox lucius L.)
  • 2012
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 418-419, s. 69-74
  • Tidskriftsartikel (refereegranskat)abstract
    • The strontium (Sr) or Sr:Ca ratio in otoliths has been widely used in the last decade to describe the migration histories of fish between fresh and marine waters. However, reference experimental studies of particular species and waters are necessary to confirm the underlying assumptions and evaluate the applicability of this tool to field data. Laboratory experiments indicated that juvenile, anadromous pike (Esox lucius L) from the Baltic Sea reared in successively increasing salinities (from 0 to 7 parts per thousand) for 110 d accumulated Sr in their otoliths according to a positive relationship with waterborne Sr. When the pike were given prey fish from brackish (7 parts per thousand) environments, the otolith Sr:Ca ratio increased more than in fish given prey from freshwater lakes. Pike held at constant salinity (7 parts per thousand) and given prey fish from the same salinity environment had an Sr:Ca ratio of 6.9 x 10(-3). The ratio decreased successively for fish given prey from freshwater (4.4 x 10(-3)) or kept in freshwater and given food from brackish water (3.1 x 10(-3)). Fish exposed to freshwater and given prey fish from freshwater displayed no increase in Sr:Ca ratio (1.6 x 10(-3)). The experiments demonstrated that the Sr:Ca ratio may be used to describe the migration history of pike between rivers and the Baltic Sea. The maximum Sr:Ca value for pike given marine-origin food corresponded to those of fish collected from the Baltic Sea.
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20.
  • Felisberto, Paulo, et al. (författare)
  • Acoustic monitoring of O-2 production of a seagrass meadow
  • 2015
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 464, s. 75-87
  • Tidskriftsartikel (refereegranskat)abstract
    • Acoustic data were acquired in October 2011 over a Posidonia oceanica meadow in the Bay of la Revellata, Calvi, Corsica. The purpose was to develop an acoustic system for monitoring the oxygen (O-2) production of an entire seagrass meadow. In a shallow water area (<38 m), densely covered by P. oceanica, a sound source transmitted signals in 3 different bands (400-800 Hz, 1.5-3.5 kHz and 65-8.5 kHz) toward three self-recording hydrophones at a distance of 100 m, over the period of one week. The data show a high correlation between the diel cycle of the acoustic signals' energy received by the hydrophones and the temporal changes in water column O-2 concentration as measured by optodes. The results thus show that a simple acoustic acquisition system can be used to monitor the O-2-based productivity of a seagrass meadow at the ecosystem level with high temporal resolution. The finding of a significant production of O-2 as bubbles in seagrass ecosysterns suggests that net primary production is underestimated by methods that rely on the mass balance of dissolved O-2 measurements.
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21.
  • Gerecht, A. C., et al. (författare)
  • Phosphorus availability modifies carbon production in Coccolithus pelagicus (Haptophyta)
  • 2015
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 472, s. 24-31
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract The coccolithophore Coccolithus pelagicus (Wallich) Schiller fixes CO2 into particulate organic carbon (POC) through photosynthesis and into particulate inorganic carbon (PIC) in the form of calcite. To examine the role of phosphorus (P) availability in the production of POC and PIC, C. pelagicus subsp. braarudii (Gaarder) Geisen et al. was grown in semi-continuous cultures at three initial phosphate concentrations (P-replete, 1, and 0.5 μM [P]). Reduced P-availability (1 and 0.5 μM [P]) decreased POC production, while PIC production only decreased when phosphate concentrations became growth limiting (0.5 μM [P]). This decrease has not been observed previously in batch cultures, highlighting the inadequacy of the batch culture approach with regard to determining carbon production. The reduction in growth rate by 50% at 0.5 μM [P] was accompanied by a doubling in cell volume (and POC). PIC production was halved, resulting in a lowered PIC to POC ratio. The average number of coccoliths per cell (and PIC content) remained the same among treatments, despite the significant change in cell size. Our data suggest that POC production in C. pelagicus is more sensitive towards a moderate reduction in phosphorus availability than PIC production. Once phosphorus availability limits cell division, however, phosphorus resources are invested into POC rather than PIC production. This reduces cell density and sinking rates, indicating that coccoliths do not act as ballast for reaching deeper nutrient-rich layers under nutrient limitation.
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22.
  • Hedman, Jenny E., et al. (författare)
  • Particle reworking and solute transport by the sediment-living polychaetes Marenzelleria neglecta and Hediste diversicolor
  • 2011
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 407:2, s. 294-301
  • Tidskriftsartikel (refereegranskat)abstract
    • This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind.m(-2)) and Hediste diversicolor (2 g ww, 800 ind.m(-2)) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient D(b) and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient D(a). The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). D(b) did not differ between the two species (2.4 x 10(-3) cm(2) d(-1)) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y(-1) for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min(-1) for H. diversicolor and 0.003 mL min(-1) for M. neglecta, corresponding to an area-specific rate of ca. 12 L m(-2) d(-1) at the used densities. D(a) did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.
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23.
  • Hylander, Samuel, et al. (författare)
  • UV protective compounds transferred from a marine dinoflagellate to its copepod predator
  • 2010
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 389:1-2, s. 38-44
  • Tidskriftsartikel (refereegranskat)abstract
    • Planktonic organisms living in surface waters can be exposed to harmful levels of ultraviolet radiation (UVR), but few studies have examined accumulation of UV protective compounds in marine zooplankton. Zooplankters are suggested to lack the ability to synthesize these substances and hence must accumulate them from their algal food. Here, we show that both phytoplankton (dinoflagellates) and their zooplankton grazers (copepods) respond strongly to UVR exposure by, respectively, synthesizing and accumulating the natural sunscreens mycosporine-like amino acids (MAAs). In our experiment, the MAAs content increased approximately four times in dinoflagellates exposed to UVR and PAR, as compared to non-UVR controls only receiving PAR (PAR = photosynthetically active radiation). The elevated MAAs level in the dinoflagellates was mirrored in the copepods, which accumulated more MAAs when exposed to UVR as compared to a non-UVR treatment. Overall, copepods accumulated approximately 2-5% of the total MAAs pool. Other UV protective compounds, like carotenoids, were however not accumulated by the copepods. The ability of some species to produce or accumulate photoprotective compounds may lead to increased fitness, and thus these taxa may become more dominant in plankton communities. (C) 2010 Elsevier B.V. All rights reserved.
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24.
  • Ismail, Rashid O., 1986-, et al. (författare)
  • Effects of calcification on air-water CO2 fluxes in tropical seagrass meadows : A mesocosm experiment
  • 2023
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 561
  • Tidskriftsartikel (refereegranskat)abstract
    • Seagrass meadows deliver a range of ecosystem services, where one of the more important is the capacity to store carbon and serve as sinks for atmospheric carbon dioxide. The capacity of seagrass meadows for carbon storage might, however, be modified and complicated by several factors; one important factor is the possible effects of calcification within the meadows. In tropical areas, seagrass meadows can contain high proportions of calcareous organisms, which through their calcification may cause release of CO2. To study this aspect of the CO2 balance within tropical seagrass systems, we investigated the air-water CO2 flux in seagrass mesocosms with different plant community compositions, i.e. mixtures of seagrass and calcifying macroalgae, having similar overall photosynthetic oxygen evolution rates. The measured CO2 fluxes changed both in rate and direction over the day and were significantly related to plant community composition. Downward fluxes of CO2 were found only over vegetation with high proportion of seagrass and in the afternoon, whereas occurrence of calcifying algae appeared to reverse the flow. A partial least squares (PLS) regression model indicated that pH, pCO2 and dissolved inorganic carbon (DIC) were the primary environmental variables predicting the CO2 fluxes. Our findings show that algal calcification might partly counteract the carbon sequestration in seagrass meadows.
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25.
  • Kamenos, Nicholas A., et al. (författare)
  • Attachment of the juvenile queen scallop (Aequipecten opercularis (L.)) to Maerl in mesocosm conditions; juvenile habitat selection
  • 2004
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 306:2, s. 139-155
  • Tidskriftsartikel (refereegranskat)abstract
    • Substratum un-acclimated juvenile queen scallops (Aequipecten opercularis) (< 18 mm and 1830 mm shell height) were released in equal numbers onto pristine live maerl (PLM), impacted dead maerl (IDM), gravel and sand in choice chambers. Their habitat selection was monitored over a 4-day period in control and predator treatments (utilising Asterias rubens L. and Carcinus maenas (L.)). Microhabitat use of PLM by juvenile queen scallops and the presence of cues in live maerl were also investigated.In control and predator treatments juvenile queen scallops were observed to attach preferentially to PLM than IDM, gravel or sand. Juvenile queen scallops were observed to maintain a more exposed attachment site in the absence of predators but sought refuge within and between maerl nodules in the presence of both predators. Smaller queen scallops (< 18 mm shell height) were more efficient at utilising maerl thalli as a refuge. Juvenile A. opercularis showed hierarchical cue responses mediated by predator presence, i.e. responding favourably to a factor associated with live maerl presence irrespective of heterogeneity in the absence of predators but favourably to higher maerl heterogeneity in their presence. If they also preferentially attach to PLM in the field, at some sites where PLM grounds cover large areas, they may thus be considered to constitute 'nursery areas'. Habitat attachment preference appears to be predetermined and not a result of localised predator avoidance; however, habitat usage changes in the presence of predators. Maerl beds have been shown to be easily damaged by scallop dredging in Scotland and if such nursery areas are being destroyed extensively in the field, this could damage recruitment to localised adult populations. 
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26.
  • Kamenos, Nicholas A., et al. (författare)
  • Maerl grounds provide both refuge and high growth potential for juvenile queen scallops (Aequipecten opercularis L.)
  • 2004
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 313:2, s. 241-254
  • Tidskriftsartikel (refereegranskat)abstract
    • Human damage to biogenic substrata such as maerl has been receiving increasing attention recently. Maerl forms highly biodiverse and heterogeneous habitats composed of loose-lying coralline red algae, which fulfil nursery area prerequisites for queen scallops (Aequipecten opercularis) and other invertebrates. The benefits obtained by queen scallops utilising maerl were poorly understood, so we used both laboratory predation and field tethering experiments to investigate the refuge and growth potential provided by pristine live maerl (PLM) grounds over other common substrata. In aquaria, more juvenile queen scallops (<35 mm shell height) survived on PLM than on gravel substrata in the presence of the crab Carcinus maenas or the starfish Asterias rubens. Field tethering experiments indicated similar survivorship of juvenile queen scallops on PLM and gravel; additionally, their growth rates were similar on both substrata. PLM allows scallops to seek refuge from predators and position themselves to optimise their food supply. Other bivalve refugia have been shown to provide poor food supply as a consequence of their high heterogeneity, yet maerl grounds provide a 'win-win' scallop nursery area coupling refuge availability with high food supply. 
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27.
  • Kutti, Tina, et al. (författare)
  • Metabolic responses of the deep-water sponge Geodia barretti to suspended bottom sediment, simulated mine tailings and drill cuttings
  • 2015
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 473, s. 64-72
  • Tidskriftsartikel (refereegranskat)abstract
    • Northeast Atlantic sponge beds are recognized as local hotspots for biodiversity and nutrient cycling. Despite their important functional role little is known about their sensitivity to effluents from the expanding hydrocarbon-, mining- and bottom trawling industry. Here, data on physiological and biological responses of the common demosponge Geodia barretti to short (4 h) and long-term (50 day) cyclic exposure of suspended particles are presented. The laboratory study showed that 4 hour pulse exposures with crushed rock particles at 500 mg l(-1) caused a 50% drop in oxygen consumption but with a quick recovery to pre-exposure oxygen consumption once suspended sediment loads returned to background levels. Long-term cyclic exposure (12 h each 24 h) for 29 days caused a permanent drop in oxygen consumption with 60% in sponges exposed to 50 mg l(-1) of crushed rock but with no apparent effect on the energy content of the sponge. Oxygen consumption and energy content of sponges exposed to natural bottom sediments at the same concentration remained unchanged. In conclusion, G. barretti appears to have well developed mechanisms to resist sediment stress, however, the study demonstrated that operations releasing large amounts of suspended crushed rock such as exploration drilling and submarine tailings disposal near sponge beds should be carefully planned to avoid long-term losses of benthic ecosystem functions, such as organic matter re-mineralization.
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28.
  • Lefébure, Robert, et al. (författare)
  • Temperature and size-dependent attack rates of the three-spined stickleback (Gasterosteus aculeatus) : are sticklebacks in the Baltic Sea resource-limited?
  • 2014
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 451, s. 82-90
  • Tidskriftsartikel (refereegranskat)abstract
    • The three-spined stickleback Gasterosteus aculeatus is a small omnivorous fish, widely distributed in the northern hemisphere. In the Baltic Sea, recently observed increases in their population densities have been attributed to declines of piscivorous predators. Concurrent with this predator release, an alternative hypothesis is that past and present consumption rates and resource limitation thresholds may have contributed to the recent increases in stickleback abundance. To evaluate this hypothesis, we estimated the size- and temperature-dependent attack rate and the critical resource density (CRD) of three-spined sticklebacks. We incorporated laboratory results with time series of zooplankton abundance to estimate historical trends in degrees of resource limitation in sticklebacks and evaluate if increases in individual consumption rates could be a plausible mechanism facilitating the suggested population increase. Attack rates increased with body size and temperature in laboratory experiments. Estimated CRD increased with size but decreased with temperature, suggesting that stickleback scope for individual and population growth might increase at temperatures above 15 degrees C. Our results further suggest that sticklebacks have been living closer to maximum consumption capacity in the coastal areas of the Bothnian Sea (BS) and Bothnian Bay (BB). Moreover, decreasing levels of resource limitation in the corresponding off-shore zones may have facilitated increases in stickleback densities for these areas. However, in the coastal zones of the Baltic proper (BP), resource levels have declined and are approaching the CRD, suggesting that stickleback populations in BP may not increase further. The decrease in CRD with temperature implies that increasing summer temperatures will increase the scope of individual and population growth in the three-spined stickleback and may favor the three-spined stickleback's competitive ability over other species under a warmer climate. (C) 2013 Elsevier B.V. All rights reserved.
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29.
  • Liénart, Camilla, et al. (författare)
  • Diet quality determines blue mussel physiological status : A long-term experimental multi-biomarker approach
  • 2023
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 563
  • Tidskriftsartikel (refereegranskat)abstract
    • Cyanobacterial blooms have increased worldwide and decreases in spring blooms of diatoms in temperate aquatic ecosystems are increasingly reported. Whether such shifts in the food base positively or negatively affect primary consumer's physiological status, growth, and more broadly, ecosystem functioning, is poorly known. Here, we test how a widespread filter-feeding blue mussel from the genus Mytilus reacts to diatoms, filamenous non-toxic cyanobacteria and a mixture of the two in a 50 day feeding experiment and compare with mussels in the field. We use a multi-tracer approach to assess mussels' nutritional and physiological status. Diatoms had highest relative proportions of the essential fatty acids 20:5ω3 (EPA) and 22:6ω3 (DHA), but cyanobacteria had a high relative proportion of polyunsaturated FAs (PUFAs) especially 18:3ω3, a precursor of ω3 FAs. Bulk and amino-acid-δ15N demonstrated assimilation of cyanobacterial N or diatom N by the mussels, while fatty acid (FA) composition and δ13C-FA analyses demonstrated assimilation of C and FAs from diatoms. Still, C and N from both food sources were utilized when mussels were fed the mix and condition index, scope for growth (SFG; measure of energy status) and the elemental N:P ratio of mussels where higher in mussels fed cyanobacteria only, indicating better growth status in this treatment. It seems like mussels fed cyanobacteria, a food with low proportions of essential FAs compared to diatoms, were able to cover the dietary requirements through FA biosynthesis from precursor FAs. The FA composition and δ15N-results from mussels fed cyanobacteria agreed well with seasonal field measurements of mussels. Our study provides the first feeding experiment investigating how blue mussels utilize N from cyanobacteria and shows the rather positive response to this type of food. Our results suggest that imbalances in the biochemical composition of diet of consumers can be overcome through biosynthesis of essential FAs. In the context of climate change with shifting biogeochemical baselines, it is crucial to understand the biological effects of such changes in the quality of the production base.
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30.
  • Lin, Senjie, et al. (författare)
  • Two flavodoxin genes in Trichodesmium (Oscillatoriales, Cyanophyceae): Remarkable sequence divergence and possible functional diversification
  • 2009
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 371:1, s. 93-101
  • Tidskriftsartikel (refereegranskat)abstract
    • We analyzed flavodoxin gene sequences and transcription patterns in the marine nitrogen-fixing cyanobacterium Trichodesmium Ehrenberg ex Gomont 1892. While a typical cyanobacterial flavodoxin ortholog (fld1) was identified from cultured (strain IMS101) and environmental Trichodesmium by PCR and Southern blot hybridization, a second flavodoxin (fld2) was identified in the genome sequence. BLAST and phylogenetic analyses indicated that the two fld genes were highly divergent: fld1 was most closely related to fld common in cyanobacteria, wheras fld2 formed a distinct cluster with a fld so far only found in the unicellular diazotrophic cyanobacteria Cyanothece and Crocosphaera (in which fld2 was the only fld). The fld2 cluster was more closely allied with a fld in non-cyanobacterial diazotrophs such as Azotobacter and Azoarcus than fld1 in other cyanobacteria. This result suggests different evolutionary history of these two genes. Real-Time RT–PCR analysis on iron-replete and iron-deplete Trichodesmium cultures revealed remarkable diel dynamics in transcription of both flds but surprisingly failed to show induction under iron stress. Addition of nitrate to these cultures depressed nifH and fld2 transcription while elevating the transcription of fld1 in iron-stressed cultures. A positive correlation between fld and nifH transcript abundances was found, which was stronger in the case of fld2 than fld1. Our data suggest that these two flavodoxins in Trichodesmium may be functionally diversified and that use of flavodoxin as an iron stress indicator needs to be validated for each organism with consideration of diel dynamics of gene expression.
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31.
  • Meunier, Cedric Leo, et al. (författare)
  • Impact of swimming behaviour and nutrient limitation on predator-prey interactions in pelagic microbial food webs
  • 2013
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 446, s. 29-35
  • Tidskriftsartikel (refereegranskat)abstract
    • Heterotrophic dinoflagellates are motile protozoans, important consumers of phytoplankton in aquatic environments. Motility is a main advantage for predators during grazing activities, but can also serve as defence mechanisms against being grazed. Thus, numerous microalgal species are also motile. We hypothesise that the nutrient status of an organism affects its swimming speed and especially that nutrient limitation has a negative impact on cell motility. Such altered motility of both predator and prey should influence feeding success of grazers. We tested those hypotheses by investigating the impact of nutrient (phosphorus) limitation on motility of two algal species, Rhodomonas sauna and Teleaulax sp., and the heterotrophic dinoflagellate Oxyrrhis marina and examined how differences in prey swimming speed affect grazing of O. marina. We show that nutrient limitation had a strong impact, reducing algal swimming speed and escape success and in turn significantly influencing food uptake of O. marina which was maximal for intermediate prey swimming speed. We also tested the importance of algal behaviour on O. marina selective feeding and observed that Teleaulax sp. presented an escape behaviour, which appeared to be an effective defence mechanism against grazing of O. marina. While this study has focused on the trophic interactions between two algal species and one dinoflagellate, the impact of nutrient limitation and escape strategy on feeding success of the predator is likely to be found in the whole range of plankton trophic interactions.
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32.
  • Nascimento, Francisco, et al. (författare)
  • Settling cyanobacterial blooms do not improve growth conditions for soft bottom meiofauna
  • 2009
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier B.V. - 0022-0981 .- 1879-1697. ; 368, s. 138-146
  • Tidskriftsartikel (refereegranskat)abstract
    • Summer blooms of the toxin-producing cyanobacteria Nodularia spumigena are frequent in the Baltic Sea and recent findings suggest that they may be an important food source for the benthos below the euphotic zone. To investigate the effects of settling spring and summer phytoplankton blooms on meiofaunal growth, we assayed concentrations of nucleic acids in three ostracod species (Candona neglecta; Heterocyprideis sorbyana and Paracyprideis fennica) and one genus of nematodes (Paracanthonchus spp.) after incubation in sediments with the one of the following food additions: (1) diatoms, (2) the cyanobacterium Nodularia spumigena, (3) Tetraphyll® as a known high-quality food source, (4) lignin as a refractory artificial food, and (5) control (no added organic matter). The ribosomal ribonucleic acid (RNA) content and RNA:DNA ratios of the tested organisms were lower in the cyanobacteria treatment than in the diatom treatment, with the difference in RNA:DNA ratios being statistically significant for all species except C. neglecta. Moreover, individuals incubated with N. spumigena showed RNA:DNA levels similar to those found in the lignin and control treatments. Furthermore, N. spumigena had lower concentrations of both enzymatically hydrolysable amino acids (EHAA) and eicosapentaenoic acid (EPA) than diatoms suggesting lower nutritional quality for consumers. These results indicate that recently settled summer blooms of N. spumigena are nutritionally poor and do not improve conditions for meiofaunal growth in Baltic sediments. In contrast, input of diatoms to the sediments during spring is crucial for meiofaunal growth.
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33.
  • Strömberg, Helena, et al. (författare)
  • Effects of territorial damselfish on cryptic bioeroding organisms on dead Acropora formosa
  • 2005
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 327:1, s. 91-102
  • Tidskriftsartikel (refereegranskat)abstract
    • Many damselfishes exclude other grazers from their territories and “farm” filamentous algae within their territories. In this study the indirect effect of damselfish territories on faunal composition and abundance of internal bioeroders of dead Acropora formosa (Dana, 1846) was investigated in territories of two damselfish species, Stegastes nigricans (Lacepède, 1802) and Plectroglyphidodon lacrymatus (Quoy and Gaimard, 1825). S. nigricans tends to be more protective and defend their territories more aggressively than P. lacrymatus. Newly killed branches of A. formosa were placed inside and outside damselfish territories, for 1 or 2 years, at a coral reef near Zanzibar, Tanzania. As predicted, the coral branches became covered with more filamentous algae in the S. nigricans territories than in the controls, with intermediate levels in the P. lacrymatus territories. Among the internal bioeroding fauna, polychaetes were by far the most common group. In total, there were significantly more borers in the first year than the second, which was mainly due to a high abundance of sabellids. Furthermore, sabellids were significantly more abundant in control areas and in the P. lacrymatus territories compared to the S. nigricans territories. However, many other genera showed the opposite pattern, with more polychaetes in the fish territories compared to the controls. There was also a clear difference in assemblage structure between S. nigricans territories and controls. Thus, we found strong effects of whether a piece of coral was placed inside or outside a damselfish territory on the abundance of many of the bioeroding taxa. We discuss multiple reasons for these indirect effects of the territories, including that deposit feeding bioeroders may benefit from the dense algal turf found inside the territories whereas suspension feeding bioeroders may benefit from substrate with less filamentous algae found outside territories. Considering our results in the context of the large areas of coral reefs that typically are defended as territories by damselfishes, these fish are likely to have a considerable impact on the boring community of a coral reef.
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34.
  • Vehmaa, Anu, et al. (författare)
  • How will increased dinoflagellate:diatom ratios affect copepod egg production? : a case study from the Baltic Sea
  • 2011
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 401:1-2, s. 134-140
  • Tidskriftsartikel (refereegranskat)abstract
    • Mild winters are modifying the plankton spring bloom composition so that diatoms are decreasing and dinoflagellates increasing. We used two common spring bloom phytoplankton species, a diatom and a dinoflagellate to study the effects of changing bloom composition on the reproduction of the calanoid copepod Acartia bifilosa Giesbrecht, a dominant species in the northern Baltic Sea. Egg production was significantly higher when copepods were fed with Scrippsiella hangoei (Schiller) Larsen dinoflagellates or a mixture of Scrippsiella and Skeletonema marinoi Sarno and Zingone diatoms than when they were provided with Skeletonema only. This effect was observed despite the fact that the Skeletonema strain did not produce polyunsaturated aldehydes (PUAs) and its nutritional quality was high according to polyunsaturated fatty acid (PUFAs) and sterol measurements, and moderate according to mineral (C:N and C:P) measurements. When offered mixtures of Skeletonema and Scrippsiella, copepods ingested both, even when the other one was rare. This indicates potential positive effect of multispecies diets not verified in this study. Here we show that increasing dinoflagellate:diatom ratio might have a positive effect on copepod reproduction.
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35.
  • Villnas, Anna, et al. (författare)
  • Multi-level responses of Macoma balthica to recurring hypoxic disturbance
  • 2019
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 510, s. 64-72
  • Tidskriftsartikel (refereegranskat)abstract
    • The frequency of seasonal and short-term hypoxia is increasing in coastal seas. How such repeated disturbances affect key species that have important roles for ecosystem processes and functions remains, however, unknown. By performing a field experiment we explored if the bivalve Macoma balthica can cope with short-term, recurring hypoxic stress, and investigated how hypoxia affects the condition of surviving bivalves. By combining data on different levels of biological organization, i.e., on physiology (biomarker response), behaviour and demography, we identified stress responses before the population declined. One pulse of hypoxic disturbance (3 days) resulted in behavioural alterations, as adult M. balthica extended their siphons, emerged towards the sediment surface and expressed decreased reburial rates. However, the demographic structure of the population remained unaltered. Several pulses of recurring hypoxic stress resulted in physiological response with changes in glutathione reductase and acetylcholinesterase enzyme activities. The recurring hypoxic disturbance was observed to affect juvenile bivalves before adults, while pro-longed hypoxia reduced the entire bivalve population. Our results clearly show that hypoxic stress changes the behaviour and physiology of M. balthica before demographic changes occur, which is likely to have severe implications for the contribution of this key species to ecosystem functioning. That a combination of measures at different levels of organization can detect disturbances at an early stage suggests that such an approach would be useful for assessing the effects of disturbances on marine ecosystems that are increasingly affected by anthropogenic change.
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36.
  • Waldeck, Peter, et al. (författare)
  • Effects of winter water temperature on mass loss in Baltic blue mussels : Implications for foraging sea ducks
  • 2013
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 444, s. 24-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Water temperature may through its effects on body mass, reproductive output and recruitment of bivalves also influence organisms higher up the food chain. The small sized Baltic blue mussel (Mytilus trossulus × Mytilus edulis) is a dominant key species in the Baltic Sea food web and it is an important food source for sea ducks such as the common eider (Somateria mollissima) and the long-tailed duck (Clangula hyemalis) and for some species of fish. Possible links between winter water temperature and the quality of blue mussels as food for wintering sea ducks were investigated by measuring the soft body mass loss of mussels during winter in an experimental set-up and in the field. Results demonstrated that warmer water temperatures in winter had a significant negative effect on soft body mass of Baltic blue mussels. Analysed mussels, on average 15 mm in length, kept in experimental aquaria between January and March and exposed to a 3.6 °C elevated water temperature regime corresponding to conditions during mild winters, had about 11% smaller tissue dry mass in March than mussels exposed to a water temperature regime corresponding to conditions in cold winters. At two field study areas, the body mass loss of mussels from October to March in a mild winter was significant and more pronounced (15% and 19%, respectively) than in a cold winter (11% and 4% respectively). This difference is of importance because in winter and spring, sea ducks build up energy stores for the subsequent breeding season by consuming large quantities of blue mussels and the energy gain of the birds per dive will be affected by the soft body tissue content of the mussels. The results improve our possibilities to predict the seasonal and yearly variation of the quality of the main food of sea ducks and help us to better understand the causes for the variable reproductive success and the present population declines of sea ducks. The results may also improve our possibilities to model the effects on Baltic Sea food webs of possible future increases in water temperature.
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37.
  • Westerberg, Håkan (författare)
  • Predation on migrating eels (Anguilla anguilla L.) from the Western Mediterranean
  • 2021
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 544
  • Tidskriftsartikel (refereegranskat)abstract
    • Nineteen female silver European eels (Anguilla anguilla L.) were tagged with satellite tags and released in the Gulf of Lion in the Mediterranean during the migration seasons 2013 and 2015. Sixteen tags transmitted data: five in the Atlantic Ocean, and eleven in the Mediterranean. Of those, 50% of migrating eels were consumed by marine mammals in each year, all in the Mediterranean. The diving behaviour recorded by the tags after the eels were consumed indicated that the most likely predators were deep diving toothed whales. Measurements of the acoustic target strength of the tag showed a negligible effect on the detectability by whale biosonar. Overall, the observed predation rate was similar to that reported for eels escaping into the Atlantic. However, unlike eels in the Atlantic, which are most vulnerable to predators in the first week of escapement as they traverse the continental shelf and before they reach the refuge of the deep ocean, eels escaping from the Mediterranean were predated in deep water, months after release, likely as a consequence of their migration within a relatively narrow and deep corridor in the Alboran Sea. This emphasises the challenge of accounting for natural mortality in management plans for the long-term recovery of the European eel.
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38.
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39.
  • Turner, J. T., et al. (författare)
  • ZOOPLANKTON FEEDING ECOLOGY - GRAZING DURING ENCLOSURE STUDIES OF PHYTOPLANKTON BLOOMS FROM THE WEST-COAST OF SWEDEN
  • 1992
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 157:1, s. 19-31
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of grazing on natural phytoplankton populations was examined during enclosure studies on the effects of nutrients, zooplankton, and ctenophores on phytoplankton bloom dynamics on the west coast of Sweden in May, 1990. Grazers included the copepods Acartia clausi Giesbrecht, Centropages hamatus Lilljeborg, and Oithona similis Claus, and the marine cladoceran Podon polyphemoides Leuckart. These species ingested various diatoms, dinoflagellates and athecate microflagellates, but grazing was minimal. Clearance rates of the copepods were < 1 ml.animal-1.h-1, while those of cladocerans reached 2.5 ml.animal-1.h-1, at microflagellate concentrations of 1442-3519 cells.ml-1. Despite the low levels of copepod and cladoceran grazing, there was considerable removal of Chl a by grazers < 90-mu-m in longest dimension. These micrograzers were present in experimental and control containers. Athecate ciliates < 20-mu-m in longest dimension were abundant (up to 1730 cells.ml-1) in some samples, and these ciliates were the most probable micrograzers. Rates of clearance of these ciliates by A. clausi (0.13-0.81 ml.animal-1.h-1) and C. hamatus (0.46-0.81 ml.animal-1.h-1) were high, even though ciliates were less abundant than most co-occurring phytoplankton taxa. Copepod and cladoceran grazing appeared to have little impact on phytoplankton dynamics. Rather, copepods were selective consumers of the ciliates that were probably the dominant grazers.
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40.
  • Cervin, Gunnar, 1967, et al. (författare)
  • Do littorinids affect the survival of Ascophyllum nodosum germlings?
  • 1997
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 218:1, s. 35-47
  • Tidskriftsartikel (refereegranskat)abstract
    • The survival of germlings of the brown alga Ascophyllum nodosum on the west coast of Sweden were investigated in two field experiments. In the first experiment the role of Littorina fabalis, L. littorea, L. obtusata and L. saxatilis for the survival of 5 days old germlings were tested at two spatial scales, by comparing plots cleared of Littorina spp with plots holding the natural composition of the snails. The second experiment tested the effect of Littorina littorea and the exclusion of mesoherbivores other than littorinids on the survival of 13 days old germlings placed in cages. The treatments were cages with and without L. littorea and two mesh sizes (1.4 and 6.3 mm respectively), where the finer mesh was thought to exclude the mesoherbivores. There were no detectable effects of Littorina spp in the first experiment despite a low survival of the germlings. Significant differences in the survival of germlings were found between plots within a shore on a spatial scale of 2 to 30 m, but no significant differences were found between shores about 1 km apart. In the second experiment L. littorea had a negative effect on the survival of the germlings, and there was a lower level of survival of the juveniles in the cages with a larger mesh size compared to those with a finer mesh size. It is suggested that the difference in effect between the cages with different mesh sizes is due to the difference of accessibility for mesoherbivores of different sizes and that it is not caused by physical alterations by the cages. Our experiments showed that Littorina spp had no effect on the survival of germlings of A. nodosum unless in cages at abundances higher than those naturally occurring in the area at this time. Further, the experiments suggest that other mesoherbivores such as isopods and amphipods are important grazers on A. nodosum germlings. (C) 1997 Elsevier Science B.V.
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41.
  • Morford, Jennifer L., et al. (författare)
  • Sampling marine pore waters for Mn, Fe, U, Re and Mo: Modifications on diffusional equilibration thin film gel probes
  • 2003
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285-286, s. 85-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Pore water metal profiles are important for identifying redox horizons and understanding trace metal geochemical cycling. The challenges of pore water sampling for trace metals are minimizing disturbance, especially at the sediment–water interface, and minimizing oxidation during sampling. We are investigating diffusional equilibration in thin films (DET) probes for obtaining pore water profiles. Our goal is to use probes for redox-sensitive trace metals U, Re and Mo, in addition to Mn and Fe, in coastal marine areas. Initial solution equilibration tests and laboratory core incubation experiments suggest that equilibration times for probes in sediments are approximately 24–48 h. Control tests suggest that the incubation does not alter the redox conditions in the pore waters. Pore water profiles from cores sampled by slicing, centrifuging and filtering (in a nitrogen atmosphere) and from probes are similar. Two modifications on the gel probe design were tested to determine their impact. (1) PVC wedges were attached to the backs of probes to increase the contact between sediments and the probe surface and to reduce the risk of forming channels along the probe surface, which might allow vertical pore water transport. Lower Fe concentrations were measured from probes without PVC wedges, but other metal profiles were similar. (2) A modified face frame was removed from the front of a probe, to reduce disturbance of the sediments during insertion and to increase the contact between the sediments and probe surface. Probes with modified face frames did not have increasing U and Mo concentrations with depth, whereas two of the three probes without face frames did have increasing concentrations. Increasing U and Mo concentrations at depth may be reflecting the influence of irrigating burrows and their supply of oxygen to reduced sediments, which could oxidize previously reduced metals. The distribution of burrows is heterogeneous and resulting profiles would also be expected to be heterogeneous in their response. Differences between probe profiles and sliced/centrifuged profiles are examined to gain insight into possible sampling artifacts. Peaks in the Re sliced/centrifuged profiles suggest a large Re flux to the overlying waters, which is neither calculated from probe profiles nor measured in benthic chamber samples. It is possible that heterogeneity at the sampling site in Buzzards Bay resulted in these differences; however, it is also possible that centrifugation releases Re from pore structures that would not be measured with less intrusive sampling methods, such as gel probes or benthic chambers.
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42.
  • Roegner, C., et al. (författare)
  • Transport of Recently Settled Soft-Shell Clams (Mya Arenaria L.) in Laboratory Flume Flow
  • 1995
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 187:1, s. 13-26
  • Tidskriftsartikel (refereegranskat)abstract
    • A laboratory flume was used to examine the retention of juvenile soft-shell clams (2 wk postsettlement) in sediment when exposed to flow. Clams resisted erosion until the initiation of sediment transport, after which they were rapidly advected from sections of test substrate. Comparisons between living and killed clams indicated that burrowing behavior was instrumental for maintaining position in flow I the critical erosion velocity for sediment movement. The ability of low density, shallow-burrowing juvenile bivalves to avoid transport as bedload or resuspended particles is probably minimal during erosional periods, despite that fact that the position of larger, deeper living individuals may be unaffected, In energetic regimes, infaunal recruitment patterns can be dominated by hydrodynamic forces affecting juveniles.
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43.
  • Abreu, Paulo Cesar, et al. (författare)
  • Importance of biofilm as food source for shrimps (Farafantepenaeus paulensis) evaluated by stable isotopes (∂13C and ∂15N)
  • 2007
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 347:1-2, s. 88-96
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract The contribution of biofilm and artificial feeds for the growth of the pink shrimp Farfantepenaeus paulensis reared in tanks and net cages were evaluated by using stable isotope (δ13C and δ15N) analysis. In the net cage experiment, mass balance and mixing equations showed that the biofilm contribution to shrimp growth was over 49% of carbon and 70% of nitrogen. These data suggest that the artificial feed offered in this experiment, although ingested, was not properly incorporated in the shrimp tissue. In contrast, biofilm growing in tanks contributed little to the nitrogen incorporated by the shrimp (maximum of 29%). In this experiment, shrimp presented an unusually large isotope fractionation. These results imply that the shrimp are selectively ingesting some items from the biofilm, or differentially assimilate specific items of the artificial feed, due to differential digestibility. The hypothesis of selective feeding of biofilm microorganisms was corroborated in the experiment with net cages, where shrimp preferentially consumed centric diatoms. This study also demonstrated that shrimp biofilm consumption and the presence of artificial feed largely influenced biofilm formation. The consumption of centric diatoms by shrimp seem to stimulate biofilm chlorophyll-a, while biofilm δ15N values measured in tanks indicate that microorganisms present in the biofilm absorbs nitrogen released by artificial feed after its decomposition.
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44.
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45.
  • Araujo, R., et al. (författare)
  • The role of disturbance in differential regulation of co-occurring brown algae species: Interactive effects of sediment deposition, abrasion and grazing on algae recruits
  • 2012
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 422-423, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • Disturbance is an important structuring factor in intertidal communities. This study aimed at experimentally testing the effects of three important sources of disturbance to intertidal rocky habitats (abrasion, sediment deposition and herbivory) on the survivorship and growth of embryos of canopy forming fucoid species (Fucus vesiculosus and Fucus serratus). Natural levels of sediment deposition and herbivore density were characterized and the temporal variation of populations of both species was followed. The experimental study showed that the survivorship of F. serratus embryos was negatively affected by herbivory but growth was enhanced in the presence of abrasion and herbivores. F. vesiculosus suffered the interactive negative effects of the three sources of disturbance tested, although abrasion was the most important factor affecting mortality rates of embryos. Conversely, none of the tested sources of disturbance significantly affected growth of embryos. These results highlight the importance of disturbance events in regulating species interactions which might be particularly relevant for population dynamics and persistence at the geographical borders of species' distribution. (C) 2012 Elsevier B.V. All rights reserved.
  •  
46.
  • Bayne, B. L., et al. (författare)
  • Seasonal variability in feeding behaviour, metabolic rates and carbon and nitrogen balances in the Sydney oyster, Saccostrea glomerata (Gould)
  • 2006
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 332:1, s. 12-26
  • Tidskriftsartikel (refereegranskat)abstract
    • To establish if nutrients limit the growth of bivalves requires information not only on the quality of food available, but also the animals' feeding behaviour and endogenous metabolic demands. We hypothesized that growth of the Sydney rock oyster (Saccostrea glomerata) would vary in response to seasonal changes in food quality rather than quantity. We also predicted that the oysters would show feeding preferences for nitrogen over carbon, and this behaviour would result in carbon/nitrogen (C/N) ratios for ingested and absorbed matter that would be lower than the C/N of both the seston and the oysters' estimated metabolic maintenance requirements. The experiments were done in two phases under natural conditions. In phase 1, feeding behaviour was assessed on a single occasion and the results used to pose hypotheses for testing in phase 2, which included measurements made on three occasions encompassing autumn, winter and spring conditions. Growth rates varied with changes in ambient food quality and not with the concentration of total suspended matter. Feeding behaviour responded to food quality and, in most cases, resulted in nitrogen enrichment. For example, when nitrogen was potentially limiting to growth and/or maintenance.. due to high food C/N (July) or high nitrogen demand (March), pre-ingestive selection ensured nitrogen enrichment of ingested matter and UN ratios of ingested matter which were below the maintenance requirement. However, in November, when endogenous demands indicated an increased requirement for carbon, feeding behaviour resulted in carbon enrichment, an increase in carbon conversion efficiency, and ingested C/N ratios greater than the maintenance requirement. The results support the assertion of variable feeding physiology in oysters, responsive to both exogenous (seasonal differences in carbon and nitrogen availability) and endogenous (cycles of reproduction and growth) factors. (c) 2005 Elsevier B.V. All rights reserved.
  •  
47.
  • Behrens, Jane W, et al. (författare)
  • Correlations between hemoglobin type and temperature preference of juvenile Atlantic cod Gadus morhua
  • 2012
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 413, s. 71-77
  • Tidskriftsartikel (refereegranskat)abstract
    • Atlantic cod (Gadus morhua L.) exhibits polymorphic hemoglobin variants with the HbI locus showing a strong North-South geographic cline in frequency distribution of three main types (1/1, 1/2 and 2/2). This may indicate selective advantages of the different HbI types under various temperature regimes. Despite this only one study has directly examined the temperature preference of the two homozygous types, HbI- 1/1 and HbI-2/2, whereas the preference of the heterozygote (HbI-1/2) has never previously been addressed. By exposing fish to a 4–19 °C temperature gradient in an annular preference chamber we recorded the preferred temperature of wild juvenile G. morhua of all three main Hbl types originating from an area where they co-exist. HbI-2/2 G. morhua preferred significantly cooler water (8.9±0.2 °C) compared to the HbI-1/1 group (11±0.6 °C), this difference, however, not being as distinct as previously reported. There was pronounced inter-individual variation in the temperature preference of the HbI-1/2 G. morhua ranging between 6.7 and 13.8 °C, and their overall preference (10.5±0.9 °C) did not differ significantly from either of the homozygous HbI types. Notably, the mean range of utilized temperature (temperature span between 1st and 3rd quartile) was very similar between all 3 Hbl types with 3.2–3.5 °C. Considering the complexity of a trait like temperature preference, there are clearly many other factors besides HbI type that influence the thermal biology of cod, and therefore we also investigated possible associations between genotype and temperature preference for 12 variable candidate gene single nucleotide polymorphisms (SNPs) a priori expected to be related to growth and reproduction. There were, however, no significant correlations between temperature preference and any of the candidate gene SNPs indicating that none of these polymorphisms strongly associates with thermal behavior. Considering however the high-throughput genotyping methods becoming increasingly accessible there is great potential for association studies involving many more genetic markers to identify additional genetic polymorphisms that are important for temperature preference in G. morhua. In conclusion, we support the notion of a ‘warm’ (HbI-2/2) and a ‘cold’ (HbI-1/1) Hb type, although we suggest the difference to be more subtle than previously reported. Furthermore HbI-1/2 G. morhua shows rather inconsistent thermoregulatory behavior. To obtain a more definitive picture of the extent to which thermal niches are realized under natural conditions field observations in areas where the 3 HbI types co-exist should be performed.
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48.
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49.
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50.
  • Burns,, et al. (författare)
  • Intrinsic gene expression during regeneration in arm explants of Amphiura filiformis
  • 2012
  • Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 413, s. 106-112
  • Tidskriftsartikel (refereegranskat)abstract
    • The extensive regeneration ability of ophiuroids, particularly in relation to arm re-growth following amputation, is becoming increasingly recognized as a useful model system for understanding cellular differentiation and regeneration in a whole animal context. Amputated ophiuroid arms are referred to as explants. These are able to survive for several months in seawater and, when amputated at both ends (“double amputated”), can undergo partial regeneration at one end and wound healing at the other. As such, they present a simplified and controlled regenerating model system which can potentially provide clues as to the mechanism involved in the programming and polarity of cellular differentiation. In this first investigation of gene expression in an ophiuroid explant we used cDNA microarrays in the transcriptional profiling of the proximal, medial and distal sections of double amputated explants of the temperate brittle star Amphiura filiformis. The results demonstrated an active transcriptome with extensive differential gene expression focused at the original distal part of the arm explant where the regenerating blastema was located. The transcription profiles also revealed that expression patterns showed subtle differences in the levels of gene expression rather than the presence or absence of certain genes. The sections of arm under study were no longer attached to the whole animal and therefore reduced levels of activity of some transcripts e.g. ciboulot, a gene potentially involved in cell differentiation events such as neuronal development, suggest that transcript dosage and/or relative expression of certain gene combinations may play an important role in the progression of cellular differentiation events.
  •  
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