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- Engkvist, Ola, et al.
(författare)
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On the relation between retention indexes and the interaction between the solute and the column in gas-liquid chromatography
- 1996
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Ingår i: Journal of chemical information and computer sciences. - : American Chemical Society (ACS). - 0095-2338 .- 1520-5142. ; 36:6, s. 1153-1161
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Tidskriftsartikel (refereegranskat)abstract
- Gas-liquid chromatography retention indexes for organic molecules are determined by the interaction between the molecule and the column liquid phase. In this article, a model for calculating the interaction energy between a molecule and a dielectric wall is developed. The model is at least to our knowledge the first attempt to predict retention indexes from the interaction between the molecules and the column. This approach to predict retention indexes is radically different from methods proposed before. Earlier predictions of the retention indexes have been done by a large number of descriptors, which were Linearly correlated to the retention indexes. The developed model has been tested for polycyclic aromatic hydrocarbons mainly with a molecular weight of 302. For the molecules with MW 302 the obtained correlation coefficient is 0.92. A somewhat simpler model is used to fit PAH with different MWs. A correlation coefficient of 0.998 is obtained if the retention indexes were fitted to the logarithm of the interaction energies between the PAHs and the column.
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| 4. |
- Engkvist, Roland
(författare)
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Grazing in Macroalgae Communities of the Baltic Sea
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fucus vesiculosus and Fucus serratus are the only large, structuring perennial brown macroalgae in the low salinity waters of the Swedish coast of the Baltic Proper. Since the 1970s there are reports of declining Fucus vesiculosus stands from several locations around the Baltic Proper, but also indications of recoveries e.g. in Finland, in the Askö area of the northern Baltic proper and in the south east coast of Sweden. There are probably several causes for these changes. This thesis focuses on how, among biological and other factors, grazing may be the proximate factor to structure the rocky phytal zone of the Baltic Sea. Destructive effects on F. vesiculosus may be connected to extreme densities of grazers. In a field survey large densities of the potential mesograzer Idotea baltica correlated positively with grazing injuries on and reduced depth penetration of Fucus vesiculosus. In a grazing experiment biomass of F. vesiculosus was halved within two weeks at a grazer density found in the field (80 I. baltica per 100 g of Fucus wet weight). In a second survey large numbers of the gastropods Theodoxus fluviatilis and Lymnaea peregra coincided with unsuccessful recruitment of F. vesiculosus. In an experiment these gastropods grazed germlings of F. vesiculosus up to sizes of 0.8 and 1.0 mm respectively. Abundances of gastropods were highest in autumn, indicating that autumn reproductive F. vesiculosus might be more influenced than spring reproductive F. vesiculosus as the latter would have surpassed the critical size in autumn. Grazing may be modified by environmental factors. Comparatively small densities of Theodoxus fluviatilis correlated positively with abundances of Fucus vesiculosus and negatively with abundances of filamentous algae. Grazing effects advantageous to F. vesiculosus were tested in a field experiment with manipulation of grazers, nutrients and propagules of filamentous algae. At low nutrient loads grazers tended to clear the substrate from filamentous algae and strengthen the competitive ability of F. vesiculosus. At high nutrient loads the grazers could not prevent dominance of filamentous algae with detrimental effects to F. vesiculosus. Physical factors like wave-action may also modify grazing effects. In a wave-exposed coastline with mixed stands of perennial brown algae and frequent occurrences of grazing isopods, F. vesiculosus declined faster than F. serratus. In an experiment F. vesiculosus was more heavily grazed than F. serratus, but only at intense water motion. Thus F. serratus seem to have a competitive advantage to F. vesiculosus in wave exposed coasts where severe grazing occurs. The fact that the grazer I. baltica often has been connected with F. vesiculosus, might indicate that this animal would be dependent on F. vesiculosus as habitat and/or food. In a wave-exposed habitat on the eastern coast of Öland, probably earlier dominated by F. vesiculosus but now holding discrete patches of either red algae {Polysiphonia fucoides) or saw-wrack (F. serratus) I. baltica used both species as habitat and food. In addition to the two macroalgae faecal pellets contained 30-40 % microalgae, indicating that mixed diets may be important for this species. In monitoring programs of rocky bottom communities fixed sites may be revisited on a yearly bases to estimate the development of the community. There is an underlying assumption that the observations at a fixed site are representative to surrounding areas. This assumption was tested along a 350 km coastline in SE Sweden. 18 years of observations were evaluated and compared to complementary sites. Within areas of similar wave exposure there was good agreement between fixed sites and surrounding areas. When all fixed sites within wave-protected areas were analysed together for long-term trends, there was an agreement in development between sites över the whole geographic area. The Fucus community increased its distribution during the 1980s, decreased during the early ]990s (probably from grazing as described above), to increase again in 2000-2001, that is an oscillating pattern is suggested. In wave-exposed sites, along a 100 km coastline, the F. vesiculosus stands were destroyed, seemingly by grazing as described above, around 1992-1994, with no signs of recovery as late as in 2002. The results are discussed in the context of grazing, regulation of grazing by predation, eutrophication and physical factors. The importance of the lack of fish predators is suggested for further research.
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| 7. |
- Engkvist, Roland, et al.
(författare)
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Utbredning av blås- och sågtång i Kalmar och och Blekinge län: utvärdering och kvalitetssäkring av regionala data
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Tångsamhällena i sydöstra Sverige följs inom den regionala recipientkontrollen genomregelbundna besök av dykare på ett antal fasta lokaler. I Kalmar län besöks lokalerna en gångom året sedan 1980-talets början, i Blekinge län minst vartannat år sedan 1990. År 2000återbesöktes ett stort antal extra lokaler som tidigare endast besökts vid enstaka tillfällen isamband med andra miljöundersökningar. Målet med denna rapport är att beskrivautvecklingen av blås- och sågtångens utbredning i länen samt att utvärdera om data frånrecipientkontrollen är representativ för omgivande kustområden.
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| 8. |
- Engstedt, Olof, 1980-, et al.
(författare)
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Elemental fingerprinting in otoliths reveals natal homing of anadromous Baltic Sea pike (Esox lucius L.)
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Northern pike (Esox lucius) inhabit the coastal areas of the Baltic Sea. A large part of the fishes show anadromous behaviour and spawn in streams and rivers but spend most of the time foraging in the sea. We examined spawning migration in four streams in the southwest part of the Baltic, situated within a radius of 50 km. Using juvenile pike in the streams as references, otolith analysis by microPIXE revealed unique elemental patterns (Sr, Zn, Br, Co and Mn) for the juveniles in each of the four 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 (size of juveniles). Adult marked pike in their migrating spawning phase were caught in each of the streams and otoliths were analysed. Defining earlier freshwater origin by the Sr signal from the otolith core to the increase in Sr when the fish as juvenile pike migrated to the sea, element composition was determined. A principal component analysis showed that the elemental fingerprint during the freshwater phase several years back was similar for adult fish and juveniles inhabiting the stream today. The results indicated native homing of the adults to a specific stream, a process further corroborated by results from electronic marking (Pit-tags) with the return of adult individuals over several consecutive years. We interpret the results as evidence that pike in the Baltic Sea consists of several sub-populations and are developed by homing to specific spawning streams. The results of the study may have implications for fishery management as pike in the Baltic Sea cannot be seen as homogenous “stock“, but instead consists of different, unique populations similar to the pattern demonstrated in salmon (Salmo salar).
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| 9. |
- Engstedt, Olof, et al.
(författare)
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Elemental fingerprinting in otoliths reveals natal homing of anadromous Baltic Sea pike (Esox lucius L.)
- 2014
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 23:3, s. 313-321
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Malm, Torleif, et al.
(författare)
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Bentiska processer på och runt artificiella strukturer i Sveriges kustvatten
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inom de närmaste decennierna kommer sannolikt vindkraftsparker med en utbredning på många kvadratkilometer att byggas i svenska kustvatten. Dessa installationer kan påverka miljön med dess ekologiska samhällen på olika sätt; till exempel genom den redan kända reveffekten, genom att populationsstrukturen hos viktiga predatorer som fisk och mussel- och fiskätande fåglar kan förändras, eller genom förändrade strömmar som kan gynna vissa arter, främst mjukbottenarter, medan andra arter missgynnas. Därigenom kan trofiska kaskader (födovävsinteraktioner) ner i det bentiska samhället uppstå på såväl hård- som mjukbottnar. Hur parkerna påverkar de ekologiska samhällena beror troligen i hög grad på de initiala förhållandena i de aktuella områdena. Under perioden 2005–2009 utfördes en studie i syfte att undersöka den bentiska samhällsstrukturen på hårdbottnar före och efter byggnationen av större vindkraftparker. De områden som undersöktes var, Skottarevet i Kattegatt, Lillgrund i södra Öresund, Utgrunden II i södra Kalmarsund, Kårehamn utanför nordöstra Öland samt Klasådern utanför sydvästra Gotland. Av legala och ekonomiska orsaker byggdes endast en park, Lillgrund, under projekttiden. Vi fann betydande samhällsskillnader mellan områdena på såväl art- som funktionell nivå. Den största skillnaden fann vi mellan Kattegatt och Östersjön med stora skillnader i artsammansättningen och delvis med andra funktionella grupper. Även inom Östersjölokalerna hittades betydande skillnader. Samhällena i de båda sunden hade betydligt högre biomassor av musslor per kvadratmeter än de öppna områdena vid Gotland och Öland. Även algfloran skilde sig betydligt. I sunden dominerade övergödningsgynnade fintrådiga brunalger medan bottnarna längs de öppna kusterna i högre grad var beklädda med perenna rödalger. Vindkraftsutbyggnaden vid Lillgrund påverkade de bentiska samhällena måttligt men tydligt. Musslor och havstulpaner koloniserade fundament och erosionsskydd snabbt. Redan efter två år hade de artificiella och naturliga substraten en liknande samhällsstruktur. Dessutom verkar bottnarna som helhet ha påverkats av parken. Jämfört med tidigare år hade de naturliga substraten år 2009 en större biomassa av musslor och havstulpaner och en lägre biomassa av fintrådiga alger. Skillnaden var liten men signifikant.Slutsatsen av denna studie är att vindkraftsparker möjligen kan ge ekologiska effekter på bottensamhällena men att vår studie har sådana brister i geografisk och tidsmässig utsträckning att det inte säkert går att dra denna slutsats. Eftersom förhållandena runt våra kuster skiljer sig åt kan man inte dra säkra slutsatser från en plats. Det är också svårt att dra slutsatser från den korta period som förflutit sedan byggnationen av parken. Meteorologiska och oceanografiska processer som inte är relaterade till vindkraftsparken kan ha bidragit till resultatet.
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