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  • 1.
    Engkvist, Roland
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Malm, Torleif
    Nilsson, Jonas
    Possible modification of grazing effects by wave action, changing the relative dominance between Fucus serratus and Fucus vesiculosus in the southern Baltic SeaManuscript (preprint) (Other academic)
  • 2.
    Engkvist, Roland
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Malm, Torleif
    Tobiasson, Stefan
    Density dependent grazing effects by the Isopod Idotea baltica L on Fucus vesiculosus L in the Baltic Sea.2000In: Aquat. Ecol. 34: 253-260.Article in journal (Refereed)
  • 3.
    Engkvist, Roland
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Malm, Torleif
    Tobiasson, Stefan
    Density dependent grazing effects by the Isopod Idotea baltica Pallas on Fucus vesiculosus L in the Baltic Sea2000In: Aquatic Ecology, ISSN 1386-2588, Vol. 34, no 3, p. 253-260Article in journal (Refereed)
  • 4.
    Engkvist, Roland
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Nilsson, Jonas
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Malmfjärden - vatten och biologi 20112013Report (Other academic)
  • 5.
    Engstedt, Olof
    et al.
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Engkvist, Roland
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Larsson, Per
    Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
    Elemental fingerprinting in otoliths reveals natal homing of anadromous Baltic Sea pike (Esox lucius L.)2014In: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 23, no 3, p. 313-321Article in journal (Refereed)
    Abstract [en]

    We examined the element pattern in the otoliths of a migratory fish species that inhabit the coastal areas in the brackish of the Baltic Sea. The northern pike (Esox lucius) show migratory behaviour, spawning in streams and rivers and foraging in the sea. We examined spawning migration in four nearby streams in the south-west part of the Baltic. Otolith analysis by microPIXE revealed unique elemental patterns (Sr, Zn, Br, Co and Mn) for the juveniles in each of the different streams. The strontium signal in the otolith of the juveniles was used as an indicator of freshwater origin and the time spent in the stream. Adult pike in their migrating spawning phase were caught in each of the streams. The elemental composition in otoliths in their freshwater phase (using juvenile pike in the streams as references) was determined. A principal component analysis showed that the elemental fingerprint during the freshwater phase several years back in time was similar for the adult fish and for juveniles inhabiting the stream today. The results indicated natal homing of the adults to a specific stream, a conclusion that was strengthened by the fact that marked fish returned to spawn over consecutive years. Anadromous pike in the Baltic Sea may thus be divided in subpopulations. The results of the study may have implications for fishery management, as pike in the Baltic Sea cannot be seen as homogenous population.

  • 6. Malm, Torleif
    et al.
    Engkvist, Roland
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Kautsky, Lena
    Grazing effects of two freshwater snails on juvenile Fucus vesiculosus in the Baltic Sea1999In: Marine Ecology Progress Series, ISSN 0171-8630, Vol. 188, p. 63-71Article in journal (Refereed)
    Abstract [en]

    The low salinity in the non-tidal Baltic Sea excludes many species, including marine littorinoids. The only large gastropods that occur in substantial quantities in the central Baltic proper are the freshwater snails Lymnaea peregra (O.F. Müller) and Theodoxus fluviatilis (L.); both are known to consume filamentous green and brown algae. The main objective of the present study was to test the hypothesis that freshwater snails can exert substantial grazing pressure on juvenile and regenerating Fucus vesiculosus populations in the Baltic Sea. In laboratory experiments, both snail species were able to graze on F. vesiculosus germlings up to a size of approximately 0.8 to 1.0 mm. During the study period (autumn 1996 and spring and summer 1997), the largest F. vesiculosus germlings of the cohorts settled in September and May reached approximately 1.0 mm at the same time (July). Thus, to reach the 'safe' size and escape grazing requires about 8 mo for germlings settling in autumn but only 1 mo for germlings settling in spring. The survival and growth rate of new fronds from regenerating F. vesiculosus holdfasts in outdoor tank experiments were higher than for sexually recruited juveniles. After 1 yr, 95% of the holdfasts had survived, and the mean length (±SE) of the largest frond on each holdfast was 12 ± 2 mm. Grazing by L. peregra or T. fluviatilis did not affect regeneration or frond growth. During a long-term field study (1991 to 1994), an average of 8.5 ± 0.7 T. fluviatilis ind. dm-2 were found, with a maximum density of 40 ind. dm-2 in September. During a 1 yr study (1996), the average density of L. peregra was comparatively low and varied from 0.5 ind. dm-2 in April to 20 ind. dm-2 in August. The higher density found in August (L. peregra) and in September (T. fluviatilis) suggests that both species may have a grazing impact during this time. We conclude that both T. fluviatilis and L. peregra have the capacity to graze on zygotes and germlings of F. vesiculosus until they reach a safe size of approximately 0.8 to 1.0 mm. Both snail species can occasionally reach abundances high enough to affect the recruitment of F. vesiculosus. Freshwater snails do not affect the regeneration from holdfasts. However, because the time for germlings settled in autumn to reach a safe size is much longer than for germlings settled in spring, it is possible that even a low snail density has an impact on recruitment in the field. This will, however, require verification because levels of grazing activity during different times of the year are unknown.

  • 7.
    Nilsson, Jonas
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Engkvist, Roland
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Persson, Lars-Eric
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Long-term decline and recent recovery of Fucus populations along the rocky shores of southeast Sweden, Baltic Sea2004In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 38, no 4, p. 587-598Article in journal (Refereed)
    Abstract [en]

    The Fucus populations on rocky shores along 300 km of the coastal waters of southeast Sweden in the Baltic proper have been studied since 1984 at a number of fixed sites as part of monitoring programmes. This paper describes changes in distribution and abundance of F. vesiculosus and F. serratus during the period 1984–2001. Sheltered sites showed a consistent temporal and spatial pattern of Fucus spp. distribution over a coastline of 300 kilometres. The depth penetration and abundance of Fucus spp. increased during the 1980s. Around 1990 the development reversed as a consequence of grazing and in 1997 many sites were almost devoid of Fucus spp. Since 1998 both abundance and depth penetration have increased again, possibly as a result of local measures against eutrophication. Exposed sites, on the other hand, lost their Fucus populations at the beginning of the 1990s, and they have not recovered. Extended field studies lead us to deduce that the fixed sites referred to above were representative of the Fucus populations in the area investigated. Major declines, both at sheltered and exposed sites, are attributed to grazing by the isopod Idotea baltica. The populations of I. baltica may have been favoured by the continuing eutrophication of the Baltic, a series of mild winters in the 1990s, and a contemporary decline in some potential predators.

  • 8.
    Nilsson, Jonas
    et al.
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Malm, Torleif
    Stockholm University.
    Engkvist, Roland
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Interaction between isopod grazing and wave action: a structuring force in macroalgal communities in the southern Baltic Sea2004In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 38, no 3, p. 403-413Article in journal (Refereed)
    Abstract [en]

    The macroalgal belt in the southern Baltic Sea may be partly structured by the interaction of physical and biological factors. A field study, spanning the 1990s, describes a rapid decline of the Fucus spp. stands along the wave-exposed Swedish southeast coast. During this period, a relative dominance of Fucus vesiculosus L. shifted to a relative dominance of Fucus serratus L. The decline of F. vesiculosus coincided with observations of large numbers of the grazing isopods Idotea baltica (Pallas) and Idotea granulosa Rathke, or with field observations of frequent grazing marks on Fucus fronds. I. baltica, but not I. granulosa, tended to aggregate in the declining Fucus spp. stands, indicating a strong preference for Fucus spp. In a mesocosm experiment I. baltica, when given a choice, grazed both Fucus species at weak water motion. At strong water motion grazing was concentrated on F. vesiculosus. It is hypothesized that one of the reasons I. baltica preferred F. vesiculosus to F. serratus at strong water motion may have been differences in habitat quality, like width of thallus, influencing the ability to cling to the plant. Smaller thallus, as in F. vesiculosus, thus is the preferred habitat for grazing of I. blatica. We postulate that the existence of F. serratus in the area may be favoured by strong wave action and moderate but not strong grazing by I. baltica, relaxing the interspecific competition from F. vesiculosus.

  • 9.
    Svensson, P. Andreas
    et al.
    Norwegian Univ Sci & Technol, Dept Biol, NO-7491 Trondheim, Norway .
    Malm, Torleif
    Engkvist, Roland
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Distribution and host plant preference of Idotea baltica (Pallas) (Crustacea: Isopoda) on shallow rocky shores in the central Baltic Sea2004In: Sarsia, ISSN 0036-4827, E-ISSN 1503-1128, Vol. 89, no 1, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Partially due to the mass occurrence of the isopod Idotea baltica, the perennial fucoid vegetation in the Baltic Sea has been destroyed over large areas and replaced by filamentous algae. With a combination of field investigations and laboratory experiments, we tested whether I. baltica preferred Fucus serratus to the dominant red alga Polysiphonia fucoides. In the field, the I. baltica density was higher inside F. serratus than P. fucoides patches when measured per unit area, but the situation was reversed if measured per biomass algae. Diet in the field was well correlated with the distribution of the isopods. A large proportion of the isopod faecal pellets collected in the field contained remnants of microalgae, planktonic animals, and bacteria, but the dominating material was always cells from the actual host plant. In a host plant preference experiment, I. baltica distributed evenly between the two host plant types, but the isopods grazed more heavily on F. serratus. We conclude that although F. serratus is the preferred food item in a choice situation, P. fucoides appears to have the potential to support the I. baltica population with food and shelter. A possible relationship between the weak host plant preference and the low stocks of predatory fish is discussed.

  • 10. Worm, Boris
    et al.
    Lotze, Heike K.
    Boström, Christoffer
    Engkvist, Roland
    University of Kalmar, School of Pure and Applied Natural Sciences.
    Labanauskas, Vytautas
    Sommer, Ulrich
    Marine diversity shift linked to interactions among grazers, nutrients and propagule banks1999In: Marine Ecology Progress Series, ISSN 0171-8630, Vol. 185, p. 309-314Article in journal (Refereed)
    Abstract [en]

    Diverse coastal seaweed communities dominated by perennial fucoids become replaced by species-poor turfs of annual algae throughout the Baltic Sea. A large scale field survey and factorial field experiments indicated that grazers maintain the fucoid cornmunity through selective consumption of annual algae. Interactive effects between grazers and dormant propagules of annual algae. stored in a 'marine seed bank', determine the response of this system to anthropogenic nutrient loading. Nutrients override grazer control and accelerate the loss of algal diversity in the presence but not in the absence of a propagule bank. This irnplies a novel role of propagule banks for community regulation and ecosystem response to manne eutrophication.

     

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