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  • 1.
    Albertsson, Jan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Leonardsson, K
    Deposit-feeding amphipods (Monoporeia affinis) reduce the recruitment of copepod nauplii from benthic resting eggs in the northern Baltic Sea2001Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 138, nr 4, s. 793-801Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We experimentally investigated the effect of different densities of the burrowing, deposit-feeding amphipod Monoporeia affinis on the recruitment of zooplankton from benthic resting eggs. Intact sediment cores with in situ density and species composition of zooplankton resting eggs and benthic fauna were collected in the northern Bothnian Sea, part of the Baltic Sea. We removed as many M, affinis as possible from the cores and then added different numbers of ill. affinis to the cores to generate a range of densities. The cores were exposed to different densities of M. affinis for either 3 or 40 days, after which the hatched zooplankton was registered. One subset of the cores were initially incubated under low temperature (2-3 degreesC, to prevent hatching) for 37 days (the resting phase), to allow for effects of M. affinis on unhatched resting eggs. These cores were then incubated under higher temperature (13 degreesC) for 3 days (the hatching phase), to induce hatching and allow for effects on hatching or hatched specimens. In a second subset of cores with the same time and temperature schedule, the M. affinis density was experimentally reduced at the start of the hatching phase, to evaluate the effect of M. affinis during the hatching phase. To a third subset of cores, we immediately initiated the hatching phase, without an experimental resting phase, to evaluate the effects induced during the resting phase. The most common zooplankton species that hatched was Eurytemora affinis (Copepoda), followed by Bosmina longispina maritima (Cladocera). In all cores that were subjected to a resting phase, the numbers of hatched E. affinis were log-linearly negatively related to density of M. affinis. An increase of M. affinis density from 1,000 to 5,000 individuals m(-2), normal field densities, reduced the hatching by 60-70%. The negative impact was mainly exerted during the hatching phase, suggesting predation on, burial of or physical injury of hatching nauplii or eggs in a late development stage as likely mechanisms. Also, the number of B. longispina maritima that hatched was reduced by M. affinis during the hatching phase, but no clear relation to density of M. affinis could be identified. The results show that M. affinis can reduce recruitment to zooplankton from benthic resting eggs. Such impact by the benthos on resting stages of zooplankton is therefore a potentially significant link between the benthic and pelagic systems.

  • 2.
    Albertsson, Jan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Leonardsson, K
    Impact of a borrowing deposit-feeder, Monoporeia affinis, on viable zooplankton resting eggs in the northern Baltic Sea2000Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 136, nr 4, s. 611-619Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the effect of different densities of the burrowing deposit-feeding amphipod Monoporeia affinis on the potential for recruitment of zooplankton from benthic resting eggs. Hatching of resting eggs was induced in the laboratory on sliced and resuspended 1-cm depth-sections of sediment cores, collected at six stations ill an archipelago area of the Gulf of Bothnia, Baltic Sea. The uppermost 5 cm of the sediment was studied. The most common species that hatched was Eurytemor affinis (Copepoda). Individuals from another copepod genus, Acartia, hatched in significant numbers only in the cores from two stations with low amphipod abundance. Cores from stations with high amphipod densities showed a deeper distribution of emerging E. affinis nauplii compared with stations with few amphipods: the oxidised sediment layer was also deeper at high M. affinis densities than at low. Total (0 to 5 cm strata pooled) number of hatched E. affinis nauplii was independent of amphipod density. This indicates that the effect of M. affinis on E. affinis eggs involves deeper burial due to bioturbation, rather than predation. Decreased benthic recruitment of zooplankton at localities with high M. affinis density is suggested, since more deeply positioned eggs are less likely to hatch. When hatching was induced in intact, non-sliced cores from one station, the number of E. affinis nauplii that hatched was on average 43% of the number that hatched in the upper centimetre of the sliced cores from the same station. This fraction (43%), if applied to the other stations, implied a potential for benthic recruitment of up to 80000 ind m(-2) for E. affinis. Due to its high abundance, M. affinis is likely to greatly reduce benthic recruitment of zooplankton in this system.

  • 3.
    Andersson, Agneta
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Hajdu, Susanna
    Inst. f. Systemekologi, Stockholms universitet.
    Haecky, Pia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Kuparinen, Jorma
    Wikner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)1996Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 126, nr 4, s. 791-801Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A one year field study of four stations in the Gulf of Bothnia during 1991 showed that the biomass was ca. two times, and primary productivity ca, four times, lower in the north (Bothnian Bay) than in the south (Bothnian Sea) during the summer. Nutrient addition experiments indicated phosphorus limitation of phytoplankton in the Bothnian Bay and the coastal areas in the northern Bothnian Sea, but nitrogen limitation in the open Bothnian Sea. A positive correlation between the phosphate concentration and the production/biomass ratio of phytoplankton was demonstrated, which partly explained the differences in the specific growth rate of the phytoplankton during the summer. Differences in photosynthetic active radiation between the stations also showed a covariation with the primary productivity. The relative importance of nutrient or light limitation for photosynthetic carbon fixation could not, however, be conclusively determined from this study. Marked differences in phytoplankton species composition from north to south were also observed. The number of dominating species was higher in the Bothnian Sea than in the Bothnian Bay. The distribution of some species could be explained as due to nutrient availability (e.g. Nodularia spumigena, Aphanizomenon sp.), while salinity probably limits the distribution of some limnic as well as marine species. The potentially toxic phytoplankton N. spumigena, Dinophysis acuminata and Chrysochromulina spp. were common in the Bothnian Sea but not in the Bothnian Bay. The pico- and nanoplankton biomass during late summer was higher than previously reported due to a revised carbon/volume ratio.

  • 4. Burdett, H. L.
    et al.
    Carruthers, M.
    Donohue, P. J. C.
    Wicks, L. C.
    Hennige, S. J.
    Roberts, J. M.
    Kamenos, Nicholas A.
    School of Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
    Effects of high temperature and CO2 on intracellular DMSP in the cold-water coral Lophelia pertusa2014Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, nr 7, s. 1499-1506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Significant warming and acidification of the oceans is projected to occur by the end of the century. CO2 vents, areas of upwelling and downwelling, and potential leaks from carbon capture and storage facilities may also cause localised environmental changes, enhancing or depressing the effect of global climate change. Cold-water coral ecosystems are threatened by future changes in carbonate chemistry, yet our knowledge of the response of these corals to high temperature and high CO2 conditions is limited. Dimethylsulphoniopropionate (DMSP), and its breakdown product dimethylsulphide (DMS), are putative antioxidants that may be accumulated by invertebrates via their food or symbionts, although recent research suggests that some invertebrates may also be able to synthesise DMSP. This study provides the first information on the impact of high temperature (12 A degrees C) and high CO2 (817 ppm) on intracellular DMSP in the cold-water coral Lophelia pertusa from the Mingulay Reef Complex, Scotland (56A degrees 49'N, 07A degrees 23'W), where in situ environmental conditions are meditated by tidally induced downwellings. An increase in intracellular DMSP under high CO2 conditions was observed, whilst water column particulate DMS + DMSP was reduced. In both high temperature treatments, intracellular DMSP was similar to the control treatment, whilst dissolved DMSP + DMS was not significantly different between any of the treatments. These results suggest that L. pertusa accumulates DMSP from the surrounding water column; uptake may be up-regulated under high CO2 conditions, but mediated by high temperature. These results provide new insight into the biotic control of deep-sea biogeochemistry and may impact our understanding of the global sulphur cycle, and the survival of cold-water corals under projected global change.

  • 5. Burdett, Heidi L.
    et al.
    Hatton, Angela D.
    Kamenos, Nicholas A.
    School of Geographical and Earth Sciences, University of Glasgow, Glasgow, UK.
    Effects of reduced salinity on the photosynthetic characteristics and intracellular DMSP concentrations of the red coralline alga, Lithothamnion glaciale2015Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 162, nr 5, s. 1077-1085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mid- to high-latitude fjordic coastal environments experience naturally variable salinity regimes. Climate projections suggest that freshwater input into the coastal ocean will increase in the future, exposing coastal organisms to further periods of reduced salinity. This study investigated the effect of low salinity on Lithothamnion glaciale, a red coralline alga found in mid- to high-latitude fjordic regions, during a 21-day experiment. Specific measurements included: the intracellular concentration of dimethylsulphoniopropionate (DMSP, an algal secondary metabolite and major precursor to the climatically active gas dimethylsulphide), pigment composition and photosynthetic characteristics. No significant difference in intracellular DMSP concentrations was observed between treatments, suggesting that the primary function for DMSP in L. glaciale is not as a compatible solute, perhaps favouring an antioxidant role . Photosynthetic parameters (including pigment composition) exhibited a mixed response, suggesting some degree of photosynthetic resilience to reduced salinity. This study provides evidence of intracellular mechanisms adopted by L. glaciale in response to reduced salinity. This has significant implications for the survival of L. glaciale under a projected freshening scenario and provides organism-level detail to ecosystem-level projected changes should lower-salinity conditions become more frequent and more intense in the future.

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  • 6.
    Fridolfsson, Emil
    et al.
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Bunse, Carina
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Legrand, Catherine
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Lindehoff, Elin
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Majaneva, Sanna
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Hylander, Samuel
    Linnéuniversitetet, Institutionen för biologi och miljö (BOM).
    Seasonal variation and species-specific concentrations of the essential vitamin B₁ (thiamin) in zooplankton and seston2019Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 166, nr 6, s. 1-13, artikel-id 70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thiamin (vitamin B1) is mainly produced by bacteria and phytoplankton and then transferred to zooplankton and higher trophic levels but knowledge on the dynamics of these processes in aquatic ecosystems is lacking. Hence, the seasonal variation in thiamin content was assessed in field samples of copepods and in pico-, nano- and micro-plankton of two size classes (0.7–3 µm and > 3 µm) collected monthly in the Baltic Sea during 3 years and in the Skagerrak during 1 year. Copepods exhibited species-specific concentrations of thiamin and Acartia sp. had the highest carbon-specific thiamin content, at both locations. Even members of the same genus, but from different systems contained different levels of thiamin, with higher thiamin content per specimen in copepods from the Skagerrak compared to congeners from the Baltic Sea. Furthermore, our results show that the small plankton (0.7–3 µm) had a higher carbon-specific thiamin content compared to the large (> 3 µm). Additionally, there was a large seasonal variation and thiamin content was highly correlated comparing the two size fractions. Finally, there was an overall positive correlation between thiamin content in copepods and plankton. However, for periods of high thiamin content in the two size fractions, this correlation was negative. This suggests a decoupling between thiamin availability in pico-, nano- and micro-plankton and zooplankton in the Baltic Sea. Knowledge about concentrations of this essential micronutrient in the aquatic food web is limited and this study constitutes a foundation for further understanding the dynamics of thiamin in aquatic environments.

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  • 7.
    Heuschele, Jan
    et al.
    Centre for Ocean Life, National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark.
    Ceballos, Sara
    Centre for Ocean Life, National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark; Spanish Institute of Oceanography, Oceanographic Center of Gijón, Gijón, Avd. Príncipe de Asturias, Spain.
    Borg, Christian Marc Andersen
    Centre for Ocean Life, National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark.
    Bjaerke, Oda
    Department of Biosciences, University of Oslo, Oslo, Norway.
    Isari, Stamatina
    Instituto de Ciencias del Mar-CSIC, Barcelona, Spain; Institute of Oceanography, Hellenic Centre for Marine Research, Athens, Greece.
    Lasley-Rasher, Rachel
    Department of Biology, Georgia Institute of Technology, Atlanta, United States; Darling Marine Center, University of Maine, Walpole, United States.
    Lindehoff, Elin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Centre for Ecology and Evolution in Microbial Model Systems (EEMiS), Linnaeus University, Kalmar, Sweden.
    Souissi, Anissa
    Université Lille Nord de France, Lille, France; USTL, LOG, Station Marine de Wimereux, Wimereux, France; CNRS, Wimereux, France.
    Souissi, Sami
    Université Lille Nord de France, Lille, France; USTL, LOG, Station Marine de Wimereux, Wimereux, France; CNRS, Wimereux, France.
    Titelman, Josefin
    Department of Biosciences, University of Oslo, Oslo, Norway.
    Non-consumptive effects of predator presence on copepod reproduction: insights from a mesocosm experiment2014Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 161, nr 7, s. 1653-1666Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reproduction in planktonic animals depends on numerous biotic and abiotic factors. One of them is predation pressure, which can have both direct consumptive effects on population density and sex ratio, and non-consumptive effects, for example on mating and migration behaviour. In copepods, predator vulnerability depends on their sex, motility pattern and mating behaviour. Therefore, copepods can be affected at multiple stages during the mating process. We investigated the reproductive dynamics of the estuarine copepod Eurytemora affinis in the presence and absence of its predator the mysid Neomysis integer in a mesocosm experiment. We found that the proportion of ovigerous females decreased in the presence of predators. This shift was not caused by differential predation as the absolute number of females was unaffected by mysid presence. Presence of predators reduced the ratio of males to non-ovigerous females, but not by predation of males. Our combined results suggest that the shift from ovigerous to non-ovigerous females under the presence of predators was caused by either actively delayed egg production or by shedding of egg sacs. Nauplii production was initially suppressed in the predation treatment, but increased towards the end of the experiment. The proportion of fertilized females was similar in both treatments, but constantly fell behind model predictions using a random mating model. Our results highlight the importance of non-consumptive effects of predators on copepod reproduction and hence on population dynamics.

  • 8.
    Md Amin, Roswati
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Koski, Marja
    National Institute of Aquatic Resources, Technical University of Denmark, Charlettenlund, Denmark.
    Bamstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Vidoudez, Charles
    Departement of organismic and evolutionary biology, Harvard University, Cambridge, USA.
    Strain-related physiological and behavioral effects of Skeletonema marinoi on three common planktonic copepods2011Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 158, nr 9, s. 1965-1980Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three different diatom strains (9B, 1G, and 7J) induced widely different effects on Acartia tonsa physiology, and the 9B strain induced different effects for the three copepods. In contrast, different strains induced no or small alterations in the distribution, swimming behavior, and turning frequency of the copepods. 22:6(n-3) fatty acid (DHA) and sterol content of the diet typically showed a positive effect on either egg production (A. tonsa) or hatching success (P. elongatus), while other measured compounds (PUA, other long-chain polyunsaturated fatty acids) of the algae had no obvious effects. Our results demonstrate that differences between strains of a given diatom species can generate effects on copepod physiology, which are as large as those induced by different algae species or groups. This emphasizes the need to identify the specific characteristics of local diatoms together with the interacting effects of different mineral, biochemical, and toxic compounds and their potential implications on different copepod species.

  • 9.
    OQUIST, G
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik.
    HAGSTROM, A
    ALM, P
    Samuelsson, Göran
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    RICHARDSON, K
    CHLOROPHYLL-A FLUORESCENCE, AN ALTERNATIVE METHOD FOR ESTIMATING PRIMARY PRODUCTION1982Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 68, nr 1, s. 71-75Artikel i tidskrift (Refereegranskat)
  • 10. PREZELIN, BB
    et al.
    Samuelsson, Göran
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    MATLICK, HA
    PHOTOSYSTEM-II PHOTOINHIBITION AND ALTERED KINETICS OF PHOTOSYNTHESIS DURING NUTRIENT-DEPENDENT HIGHLIGHT PHOTOADAPTATION IN GONYAULAX-POLYEDRA1986Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 93, nr 1, s. 1-12Artikel i tidskrift (Refereegranskat)
  • 11.
    Samuelsson, Göran
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysiologisk botanik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå Plant Science Centre (UPSC).
    RICHARDSON, K
    PHOTOINHIBITION AT LOW QUANTUM FLUX DENSITIES IN A MARINE DINOFLAGELLATE (AMPHIDINIUM-CARTERAE)1982Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 70, nr 1, s. 21-26Artikel i tidskrift (Refereegranskat)
  • 12. Sebastian, Patrizia
    et al.
    Stibor, Herwig
    Berger, Stella
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Effects of water temperature and mixed layer depth on zooplankton body size2012Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, nr 11, s. 2431-2440Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ecological consequences of global warming include shifts of species ranges toward higher altitudes and latitudes as well as temporal shifts in phenology and life-cycle events. Evidence is accumulating that increasing temperature is also linked to reduced body size of ectotherms. While temperature can act directly on body size, it may also act indirectly by affecting the timing of life-cycle events and the resulting population age and size structure, especially in seasonal environments. Population structure may, in turn, be influenced by temperature-driven changes in resource availability. In a field mesocosm experiment, we investigated how water temperature and mixed surface layer depth (a temperature-dependent determinant of light availability to phytoplankton) affected population dynamics, population age and size structure, and individual size at stage (size at first reproduction) of Daphnia hyalina during and after a phytoplankton spring bloom. Mixed layer depth was inversely related to the magnitudes of the phytoplankton spring bloom and the subsequent Daphnia peak, but had no effect on the body size of Daphnia. Conversely, temperature had no effects on abundance peaks but strongly affected the timing of these events. This resulted in at times positive, at other times negative, transient effects of temperature on mean body size, caused by asynchronous changes in population size structure in cold versus warm treatments. In contrast to mean body size, individual size at stage consistently decreased with increasing temperature. We suggest that size at stage could be used as an unbiased response parameter to temperature that is unaffected by transient, demographically driven changes in population size structure.

  • 13. Sommer, Ulrich
    et al.
    Aberle, Nicole
    Lengfellner, Kathrin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Lewandowska, Aleksandra
    The Baltic Sea spring phytoplankton bloom in a changing climate: an experimental approach2012Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, nr 11, s. 2479-2490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The response of the Baltic Sea spring bloom was studied in mesocosm experiments, where temperatures were elevated up to 6A degrees C above the present-day sea surface temperature of the spring bloom season. Four of the seven experiments were carried out at different light levels (32-202 Wh m(-2) at the start of the experiments) in the different experimental years. In one further experiment, the factors light and temperature were crossed, and in one experiment, the factors density of overwintering zooplankton and temperature were crossed. Overall, there was a slight temporal acceleration of the phytoplankton spring bloom, a decline of peak biomass and a decline of mean cell size with warming. The temperature influence on phytoplankton bloom timing, biomass and size structure was qualitatively highly robust across experiments. The dependence of timing, biomass, and size structure on initial conditions was tested by multiple regression analysis of the y-temperature regressions with the candidate independent variables initial light, initial phytoplankton biomass, initial microzooplankton biomass, and initial mesozooplankton (=copepod) biomass. The bloom timing predicted for mean temperatures (5.28A degrees C) depended on light. The peak biomass showed a strong positive dependence on light and a weaker negative dependence on initial copepod density. Mean phytoplankton cell size predicted for the mean temperature responded positively to light and negatively to copepod density. The anticipated mismatch between phytoplankton supply and food demand by newly hatched copepod nauplii occurred only under the combination of low light and warm temperatures. The analysis presented here confirms earlier conclusions about temperature responses that are based on subsets of our experimental series. However, only the comprehensive analysis across all experiments highlights the importance of the factor light.

  • 14. Sotje, I.
    et al.
    Tiemann, H.
    Båmstedt, Ulf
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå marina forskningscentrum (UMF).
    Trophic ecology and the related functional morphology of the deepwater medusa Periphylla periphylla (Scyphozoa, Coronata)2007Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, ISSN 10.1007/s00227-006-0369-2, Vol. 150, nr 3, s. 329-343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Remotely operated vehicle (ROV)-based field studies on the distribution and behaviour of Periphylla periphylla Péron and Lesueur (Ann Mus Hist Nat Marseille 14:316-366, 1809), from three Norwegian fjords have been combined with on-board experiments and morphological and histological studies in order to understand the trophic ecology of this species. Field studies from one of the fjords showed that the zooplankton biomass was negatively related with P. periphylla abundance, indicating a predatory effect. The majority of zooplankton biomass tended to be distributed above the aggregation of P. periphylla, which in turn showed highest abundance at 100-200 m depth. Observation on the orientation of medusae passing the ROV when descending down in the water column at dawn and dusk, showed no consistency with the theory of diel vertical migration. Estimated metabolic demand of P. periphylla indicated a daily predation impact on the prey assemblage of 13% as an average for the fjord. In situ behavioural observations showed that the dominant tentacle posture of large medusae was straight upward, with tentacles extended to the oral-aboral body axis. The hunting mode alternates between ambush and ramming, whereby tentacle posture minimises the water turbulence that may otherwise alarm the prey. The musculature of the tentacles is well developed, with an especially strong longitudinal muscle on the oral side, facilitating fast movement of the tentacle towards the mouth. In addition, ring-, radial-, and diagonal musculatures are also present. The diagonal is probably most important for the corkscrew retraction of the tentacle, used at the moment of prey capture. Results from laboratory experiments show that different body-parts of P. periphylla vary in sensitivity for chemical and mechanical stimuli, including hydrodynamic disturbance and vibration in the surrounding water. Feeding success is facilitated by combining the vibration-sense on the tentacle tips and the marginal lappets, the touch-sense on the tentacle bases and marginal lappets, and a taste control of the captured prey at the mouthlips.

  • 15. Winder, Monika
    et al.
    Berger, Stella A
    Lewandowska, Aleksandra
    Aberle, Nicole
    Lengfellner, Kathrin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Sommer, Ulrich
    Diehl, Sebastian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och geovetenskap.
    Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions2012Ingår i: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 159, nr 11, s. 2491-2501Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Shifts in the timing and magnitude of the spring plankton bloom in response to climate change have been observed across a wide range of aquatic systems. We used meta-analysis to investigate phenological responses of marine and freshwater plankton communities in mesocosms subjected to experimental manipulations of temperature and light intensity. Systems differed with respect to the dominant mesozooplankton (copepods in seawater and daphnids in freshwater). Higher water temperatures advanced the bloom timing of most functional plankton groups in both marine and freshwater systems. In contrast to timing, responses of bloom magnitudes were more variable among taxa and systems and were influenced by light intensity and trophic interactions. Increased light levels increased the magnitude of the spring peaks of most phytoplankton taxa and of total phytoplankton biomass. Intensified size-selective grazing of copepods in warming scenarios affected phytoplankton size structure and lowered intermediate (20-200 mu m)-sized phytoplankton in marine systems. In contrast, plankton peak magnitudes in freshwater systems were unaffected by temperature, but decreased at lower light intensities, suggesting that filter feeding daphnids are sensitive to changes in algal carrying capacity as mediated by light supply. Our analysis confirms the general shift toward earlier blooms at increased temperature in both marine and freshwater systems and supports predictions that effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.

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