| 11. |
- Andersson, Agneta, et al.
(författare)
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Succession and growth limitation of phytoplankton in the Gulf of Bothnia (Baltic Sea)
- 1996
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Ingår i: Marine Biology. - 0025-3162 .- 1432-1793. ; 126:4, s. 791-801
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 12. |
- Andersson, Jan, et al.
(författare)
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Odling av fiskyngel i kylvattenrecipienter
- 1993
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Försök med odling av fiskyngel från larvstadiet till en för utsättningar ändamålsenlig storlek har genomförts i kylvattenrecipienterna för kraftverken i Oskarshamn och Forsmark. Abborre (Percafluviatilis) och gös (Stizostedium lucioperca) har använts som modellarter. Ett odlingssystem med flytande täta odlingskassar har utvecklats, och den enda födokällan har varit naturligt zooplankton, som insamlats med för ändamålet utvecklade anrikningssystem. Ljusets betydelse för tillväxt och överlevnad har studerats. Belysning av odlingskassama under hela dygnet har visat sig gynna tillväxten. Vidare har yngeltäthetens betydelse i relation till födotillgången undersökts. Abborre har odlats i höga tätheter med upp till 82% överlevnad och god tillväxt. Vid odlingförsök i Forsmark producerades som bäst i en enhet besatt med 25 000 abborrlarver ca 7 000 yngel med en längd av ca 3 cm; överlevnaden var alltså 28%. Gösyngel har odlats vid Oskarshamnsverket. Det sista försöksåret producerades diygt 2 000 yngel. Kannibalism har orsakat betydande mortalitet; överlevnaden var som bäst 12%. Kannibalismens orsaker diskuteras och förslag till förebyggande åtgärder framföres.
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| 13. |
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| 14. |
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| 15. |
- Andersson, Måns Sverker, et al.
(författare)
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Glycosylated haemoglobin: a new measure of condition in birds
- 1995
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Ingår i: Proceedings of the Royal Society of London. ; :260, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: The influence of condition on time of breeding and reproductive success has been discussed since Darwin first suggested a relation in 1871. We used a novel method to investigate the influence of condition on the timing of breeding and reproductive success by measuring a relatively inert physiological parameter - the amount of glycosylated haemoglobin - in blood samples taken from the collared flycatcher Ficedula albicollis. The percentage of glycosylated haemoglobin (%HbG) was assumed to be proportional to the average blood glucose level, during the 3-5 weeks before the blood sampling. The %HbG was influenced neither by sex nor age. Date of arrival at the breeding ground was negatively correlated with %HbG so that early-arriving birds had significantly higher %HbG than those arriving later. Clutch size, corrected for the effect of laying date, correlated positively with %HbG in females, as did the number of fledged young, corrected for the effect of laying date, for both sexes. We found no correlation between body mass and the %HbG. We suggest that prebreeding condition influences the timing of breeding and subsequent reproductive performance and that %HbG can be used as an indicator of prebreeding-condition in migrating birds.
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| 16. |
- Andersson, Solbritt, et al.
(författare)
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Effects of liming on the uptake of organic and inorganic nitrogen by mycorrhizal (Paxillus involutus) and non-mycorrhizal Pinus sylvestris plants
- 1997
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 135:4, s. 763-771
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Tidskriftsartikel (refereegranskat)abstract
- Seedlings of Pinus sylvestris L. were grown in Plexiglas(R) observation chambers in limed (CaCO3, pH 5.0 and 5.9) and untreated (pH 4.1) peat. The seedlings were either colonized by the mycorrhizal fungus Paxillus involutus (Batsch: Fr.) Fr. Or were non-mycorrhizal. After 18 wk in the observation chambers, N-15-labelled organic nitrogen, as lyophilized and ground mycelium of Suillus variegatus (Swartz: Fr.) O. Kuntze, or ammonium, was added to the peat. The plants were harvested after an uptake period of 14 d. Irrespective of the nitrogen form added, liming decreased both the content and concentration of N-15 in nonmycorrhizal plants, and, to a lesser extent, those in mycorrhizal plants. In mycorrhizal plants the uptake of N-15 was not correlated with area colonized by the mycorrhizal mycelium. The amount of KCl-extractable N-15 in peat without plants and mycorrhizal fungi decreased with liming. It is proposed that liming induced chemical or microbial immobilization of the added N-15. This is suggested to be the main reason for the decreased uptake of N-15 in lime treatments.
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| 17. |
- Andersson, Solbritt, et al.
(författare)
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Effects of mycorrhizal colonization by Paxillus involutus on uptake of Ca and P by Picea abies and Betula pendula grown in unlimed and limed peat
- 1996
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Ingår i: New Phytologist. - 1469-8137 .- 0028-646X. ; 133:4, s. 695-704
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Tidskriftsartikel (refereegranskat)abstract
- Uptake of P(P-32) and Ca(Ca-45) by seedlings of Picea abies (L.) Karst and Betula pendula Roth, non-mycorrhizal or mycorrhizal with Paxillus involutus (Batsch: Fr) Fr. was studied. Seedlings were grown in unamended peat (pH 4.0) or in peat limed (CaO) to pH 5.1 or 6.1. A double-labelled (P-32 and Ca-45) complete nutrient solution was added to the peat 7 wk after planting. An 8 d period was allowed for uptake of the isotopes before the seedlings were harvested. Mycorrhizal colonization clearly increased the uptake of P(P-32) in the unlimed substrate and in the substrate limed to a pH of 5.1. At the highest lime rate, the uptake of P(P-32) was greatly reduced in both mycorrhizal and non-mycorrhizal seedlings. The difference in P uptake between mycorrhizal and non-mycorrhizal seedlings was small at this lime rate. The mycorrhizal colonization of the roots was not affected by liming. However, it is possible that the mycelial growth into the substrate was inhibited. The reduction in uptake could thus be an effect of a lower availability of P in combination with a decreased fungal uptake surface at the highest lime rate. The mycorrhizal effect on uptake of Ca was much smaller than its effect on uptake of P. Mycorrhizal colonization increased the Ca(Ca-45) uptake in the unlimed treatment, where the Ca content in the substrate was very small. In the limed substrates the uptake of Ca was as high or higher in the non-mycorrhizal than in the mycorrhizal seedlings.
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| 18. |
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| 19. |
- Andre, C., et al.
(författare)
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Fertilization efficiency and gamete viability of a sessile, free-spawning bivalve, Cerastoderma edule
- 1995
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Ingår i: Ophelia. - : Informa UK Limited. - 0078-5326. ; 43:3, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- The fertilization biology of the free-spawning bivalve Cerastoderma edule was studied in the laboratory. Fertilization success declined drastically with decreasing sperm concentration. Viability of both eggs and sperm decreased with age so that no fertilization took place after 4-8 hours. A dilution model suggests that in the field sperm is rapidly diluted to concentrations that would result in very low fertilization efficiencies. The dilution process thus operates on a much smaller time scale than gamete ageing, indicating that most eggs are fertilized close to spawning males. However, it is also shown that under certain circumstances high concentrations of sperm may accumulate over dense populations of bivalves.
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| 20. |
- Andre, C., et al.
(författare)
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Predation on Settling Bivalve Larvae by Benthic Suspension Feeders - the Role of Hydrodynamics and Larval Behavior
- 1993
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 97:2, s. 183-192
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Tidskriftsartikel (refereegranskat)abstract
- Predation by the suspension-feeding infaunal bivalve Cerastoderma edule on settling C. edule larvae was studied in a flume boundary-layer flow. The density of settled larvae was reduced by 33% in an area of 5 cm2 enclosing individual adults. Mean survival time for competent C. edule larvae drifting over sediment populated with feeding adults (380 ind. m-2) was 64 s, and 75% of the observed larvae were inhaled by adults. Observations of the siphonal currents produced by C. edule and the swimming behaviour of larvae were combined in a computer model to assess the importance of adult density and boundary-layer flow on the predation risk experienced by settling larvae. Survival of settling larvae decreased drastically with increasing adult density, whereas increased flow velocity caused only a slightly higher predation risk. Although reduction in larval settlement on the scale of individual adults may be small or moderate, inhalation of settling larvae by populations of resident suspension feeders may cause a significant decrease in settlement on a larger scale (10(1) to 10(3) m).
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