| 1. |
- Götmark, Frank, 1955, et al.
(författare)
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Browsing damage on broadleaved trees in semi-natural temperate forest in Sweden, with a focus on oak regeneration
- 2005
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 20:3, s. 223-234
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Tidskriftsartikel (refereegranskat)abstract
- Absence of, or poor, oak (Quercus spp.) regeneration is a problem in uneven-aged, mixed closed-canopy broadleaved forests. Browsing by ungulates on small trees may contribute to poor oak regeneration in such forests. This possibility was investigated in 25 Swedish stands, and browsing damage was analysed in relation to landscape and stand factors. The proportion of browsed small (<20 cm tall) oak seedlings and other seedlings was low, and apparently a minor mortality factor. For saplings (20130 cm tall), accumulated browsing damage was generally higher on oak than on five major competing tree species: Fraxinusexcelsior, Corylusavellana, Tiliacordata, Acerplatanoides and Sorbusaucuparia. Leaf removal was rare in late summer, except for rowan. The amount of cover (shelter) for ungulates near plots was positively correlated with oak browsing intensity; within plots, a high density of ash saplings may reduce browsing on oak saplings. In these forests, browsing probably retards growth of oak saplings relative to competing trees. Oak may persist as a minor stand component, but monitoring is needed to study future changes.
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| 2. |
- Celander, Malin C., 1962, et al.
(författare)
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DEVELOPMENT OF ALTERNATIVE MATHEMATICAL TOOLS TO ASSESS SYNERGISTIC MIXTURE EFFECTS
- 2015
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Ingår i: 18th International symposium on Pollutant Responses in Marine Organisms (PRIMO18).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mixture effects are well known problems but chemical legislations are typically based on single chemical toxicity, which is unfortunate as chemicals occur as mixtures in the environment. There are mathematical models to assess additive mixture effects that are based on linear mixture effects such as toxicodynamic interactions. Chemicals with same or different mode-of-actions can also interfere with each other’s elimination pathways that can result in toxicokinetic interactions and cause indirect mixture effects. Therefore, chemicals that inhibit CYP enzymes in the elimination pathways of different classes of environmental pollutants can cause non-linear mixture effects that are more-than-additive. More-than-additive mixture effects have been observed between azoles and other classes of environmental pollutants such as estrogenic chemicals and aromatic hydrocarbons, as a result of toxicokinetic interactions via CYP1A/CYP3A inhibitions. There is need for new mathematical models to assess non-linear mixture effects. We have initiated the development of alternative mathematical tools to forecast non-linear mixture effects that are based on toxicokinetic interactions from earlier lab-studies in fish and fish cells. Time-dynamic is a key factor in toxicokinetic interactions and therefore we will combine multiple differential equations in the models. These equations describe how one chemical’s concentration changes over time in relationship to changes of another chemical’s concentration over time and how that affect biomarker responses such as CYP1A and vitellogenin. We will use statistical tools to quantitatively fit the suggested models with data from lab-studies. Non-linear models can be used to describe synergistic mixture effects. Those could be bottom-up-models, where we start from the different chemicals involved, or they could be top-down-models, where we fit a multi-dimension function to a given dataset using an auxiliary non-linear model. Our preliminary non-linear mathematical top-down model describes how the vitellogenin and the CYP1A biomarker responses can vary with concentrations of a synthetic estrogen and an antimycotic azole.
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| 3. |
- Enemar, A., et al.
(författare)
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Density and fluctuations of a nest-pocket breeding population of the treecreeper Certhia familiaris over a 28-year period
- 2014
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Ingår i: Ornis Svecica. - 1102-6812. ; 24:1-2, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- The number of breeding Treecreeper pairs was estimated from 1982 to 2009 in a 2.7 km2 study area located in south-western Sweden (57°39´ N; 12°4´ E). Most of the area, which was provided with 205 man-made nest pockets, is covered by broad-leafed forest. The number of first clutches varied between 5 and 21 with an annual average of 14±4.2 (SD) breeding pairs (CV 30%). The density of breeding Treecreepers varied from 1.9 to 7.8 pairs/km2 with a mean of 5.1±1.86 pairs/km2. The population did not show any statistically significant density trend over the 28 years. The between-year variation in the return rate of ringed adult females that bred after wintering was significantly negatively related to the temperature and precipitation means of the preceding winter. Thus, fewer females returned after milder winters with higher precipitation. The statistical tests pertaining to the variation in the whole breeding population indicate that the species can cope with moderate fluctuations in winter weather, thus preventing significant changes in the number of breeders in the study area.
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| 4. |
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| 5. |
- Gräns, Albin, 1979, et al.
(författare)
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Aerobic scope fails to explain the detrimental effects on growth resulting from warming and elevated CO2 in Atlantic halibut
- 2014
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 217:5, s. 711-717
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Tidskriftsartikel (refereegranskat)abstract
- As a consequence of increasing atmospheric CO2, the world's oceans are becoming warmer and more acidic. Whilst the ecological effects of these changes are poorly understood, it has been suggested that fish performance including growth will be reduced mainly as a result of limitations in oxygen transport capacity. Contrary to the predictions given by the oxygen- and capacity-limited thermal tolerance hypothesis, we show that aerobic scope and cardiac performance of Atlantic halibut (Hippoglossus hippoglossus) increase following 14–16 weeks exposure to elevated temperatures and even more so in combination with CO2-acidified seawater. However, the increase does not translate into improved growth, demonstrating that oxygen uptake is not the limiting factor for growth performance at high temperatures. Instead, long-term exposure to CO2-acidified seawater reduces growth at temperatures that are frequently encountered by this species in nature, indicating that elevated atmospheric CO2 levels may have serious implications on fish populations in the future.
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| 6. |
- Gräns, Albin, 1979, et al.
(författare)
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Effects of acute temperature changes on gut physiology in two species of sculpin from the west coast of Greenland
- 2013
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 36:6, s. 775-785
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Tidskriftsartikel (refereegranskat)abstract
- For a fish to thrive, the gut must function efficiently. This is achieved through a range of processes, including controlled patterns of gut motility and modifications in gut blood flow. The knowledge of how gut functions in fish are affected by environmental temperature is sparse, and in order to understand how changes in climate may affect fish populations, we need to understand how gut blood flow and gut motility are affected by changes in temperature. By simultaneous recording of gut blood flow, gut motility, cardiac output, heart rate and cardiac stroke volume, in vivo at 4, 9 and 14 °C, the acute thermal sensitivity of a thermal generalist (shorthorn sculpin Myoxocephalu scorpius) was compared to the more strictly Arctic species (Arctic sculpin M. scorpioides). Temperature effects on gut motility were further explored in vitro, using isolated smooth muscles. Elevated water temperatures increased gut blood flow and contractile activity. Contraction frequency increased nearly threefold and gut blood flow almost doubled with the 10 °C increase. Both cardiac output and heart rate increased with temperature, while cardiac stroke volume decreased. The cholinergic agonist carbachol was most potent on smooth muscles at 9 °C. There were no differences between the two species, suggesting that the gastrointestinal and cardiovascular systems of Arctic sculpin, although a more pronounced Arctic species, have similar abilities to cope with acute fluctuations in water temperature as shorthorn sculpin. The impact of increased gut activity at higher temperatures needs further investigation before the effects of climate change can be predicted.
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| 7. |
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| 8. |
- Gunnarsson, Bengt, 1954, et al.
(författare)
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Foraging mode of spiders affects risk of predation by birds
- 2015
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 115:1, s. 58-68
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Tidskriftsartikel (refereegranskat)abstract
- Avian insectivores are top predators of arboreal arthropods in different forest ecosystems. The selective effects of bird predation in relation to foraging behaviour in canopy-living spiders were studied in a 2-year field experiment using exclosures in a spruce forest in southern Sweden. Three different hunting strategies – free-hunting, two-dimensional web, three-dimensional web – were included in the analysis. Comparisons of bird predation rate (ratio ln (abundance net-enclosed branch/abundance control)) showed considerable variation between spider groups. Free-hunting spiders suffered most from avian insectivores and predation rate was significantly higher than in spiders with two-dimensional webs. Spiders with three-dimensional webs were exposed to a predation rate in between those of the two other hunting strategies. Generally, the experimental effect was significantly higher in spring samples than in autumn, suggesting a stronger predation pressure in winter. The high variation in susceptibility to predation by insectivores implies that selection on behaviour of spider individuals is strong. Web building in itself is probably part of the protective mechanism, suggesting that webs have dual functions. We conclude that the risk of bird predation is a selective force on foraging behaviour of spiders in a forest canopy system.
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| 9. |
- Hernroth, Bodil, 1951, et al.
(författare)
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Simulated climate change causes immune suppression and protein damage in the crustacean Nephrops norvegicus
- 2012
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Ingår i: Fish & Shellfish Immunology. - : Elsevier BV. - 1050-4648 .- 1095-9947. ; 33:5, s. 1095-1101
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Tidskriftsartikel (refereegranskat)abstract
- Rising atmospheric carbon dioxide concentration is causing global warming, which affects oceans by elevating water temperature and reducing pH. Crustaceans have been considered tolerant to ocean acidification because of their retained capacity to calcify during subnormal pH. However, we report here that significant immune suppression of the Norway lobster, Nephrops norvegicus, occurs after a 4-month exposure to ocean acidification (OA) at a level predicted for the year 2100 (hypercapnic seawater with a pH lowered by 0.4 units). Experiments carried out at different temperatures (5, 10, 12, 14, 16, and 18 °C) demonstrated that the temperature within this range alone did not affect lobster immune responses. In the OA-treatment, hemocyte numbers were reduced by almost 50% and the phagocytic capacity of the remaining hemocytes was inhibited by 60%. The reduction in hemocyte numbers was not due to increased apoptosis in hematopoetic tissue. Cellular responses to stress were investigated through evaluating advanced glycation end products (AGE) and lipid oxidation in lobster hepatopancreata, and OA-treatment was shown to significantly increase AGEs', indicating stress-induced protein alterations. Furthermore, the extracellular pH of lobster hemolymph was reduced by approximately 0.2 units in the OA-treatment group, indicating either limited pH compensation or buffering capacity. The negative effects of OA-treatment on the nephropidae immune response and tissue homeostasis were more pronounced at higher temperatures (12–18 °C versus 5 °C), which may potentially affect disease severity and spread. Our results signify that ocean acidification may have adverse effects on the physiology of lobsters, which previously had been overlooked in studies of basic parameters such as lobster growth or calcification.
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| 10. |
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