| 261. |
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| 262. |
- Persson, Anders
(författare)
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EU-klarspråk om bosättningar
- 2013
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Ingår i: Svenska Dagbladet. - 1101-2412.
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 263. |
- Persson, Anders
(författare)
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EU:s bidrag till fred
- 2011
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Ingår i: Uttryck.
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 264. |
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| 265. |
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| 266. |
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| 267. |
- Persson, Anders, et al.
(författare)
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Evaluation of Intracavity Optogalvanic Spectroscopy for Radiocarbon Measurements
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85ASAP:14, s. 6790-6798
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Tidskriftsartikel (refereegranskat)abstract
- Ever since the first publication of intracavity optogalvanic spectroscopy (ICOGS) in 2008, this novel technique for measuring the 14C/12C ratio in carbon dioxide has rendered considerable attention. As a result, there are currently at least five different research groups pursuing research on ICOGS. With a claimed limit of detection of 10–15 (14C/12C), i.e., in the same order as accelerator mass spectroscopy, achieved with a relatively inexpensive and uncomplicated table-top system, ICOGS has major scientific and commercial implications. However, during the past 5 years, no research group has been able to reproduce these results or present additional proof for ICOGS’s capability of unambiguous 14C detection, including the authors of the original publication. Starting in 2010, our group has set up a state-of-the-art ICOGS laboratory and has investigated the basic methodology of ICOGS in general and tried to reproduce the reported experiments in particular. We have not been able to reproduce the reported results concerning the optogalvanic signals dependence on14C concentration and wavelength and, ultimately, not seen any evidence of the capability of ICOGS to unambiguously detect 14C at all. Instead, we have found indications that the reported results can be products of measurement uncertainties and mistakes. Furthermore, our results strongly indicate that the reported limit of detection is likely to be overestimated by at least 2 orders of magnitude, based on the results presented in the original publication. Hence, we conclude that the original reports on ICOGS cannot be confirmed and therefore must be in error.
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| 268. |
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| 269. |
- Persson, Anders, et al.
(författare)
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Foraging behavior of benthic fish as an indicator of ecosystem state in shallow lakes
- 2007
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Ingår i: Israel Journal of Zoology. - 0021-2210. ; 53:3-4, s. 407-421
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we propose that the foraging behavior of benthic fish can be used to assess the current state of shallow lake ecosystems. Shallow lakes may display shifts between clear and turbid states, where sediment resuspension by benthivores foraging on benthic invertebrates contributes to maintaining the turbid state. We suggest that the giving-up density (GUD) of benthic fish foraging in experimental patches may provide useful information for managing shallow lake ecosystems. The rate of sediment resuspension by fish is a function of the abundance of both benthic fish and benthic invertebrates. Based on the empirical relationship between foraging behavior, habitat quality, and long-term growth prospects, and between habitat quality and rate of sediment resuspension, we conclude that systems should be more resistant to switches from a clear to a turbid state when (i) benthos biomass, maximum benthivore size, and giving up density are high, (ii) benthivore biomass is low, (iii) a low fraction of benthivore population is above the maximum benthivore size predicted from giving tip density, and when relative predation cost is high, estimated as the difference in GUD between risky and safe habitats. Although a first step, the methods introduced here should serve to facilitate predicting the probability of switching between ecosystem states, as well as to identify suitable abatement strategies for preventing such shifts.
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| 270. |
- Persson, Anders, et al.
(författare)
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Foraging capacities and effects of competitive release on ontogenetic diet shift in bream, Abramis brama
- 2002
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 97:2, s. 271-281
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Tidskriftsartikel (refereegranskat)abstract
- Bream Abramis brama) undergo ontogenetic diet shift from zooplankton to benthic macroinvertebrates, but the switching size may be highly variable. To unravel under what conditions bream are pelagic versus benthic foragers, we experimentally determined size-dependent foraging capacities on three prey types from the planktivory and benthivory niche: zooplankton, visible and buried macroinvertebrates. From these data we derived predictions of size-dependent diet preferences from estimates of prey value and competitive ability, and tested these predictions on diet data from the field. Planktivorous foraging capacity described a hump-shaped relationship with bream length that peaked for small bream of 67 mm total length. Benthivory capacity increased with increasing bream size, irrespective if benthic prey were visible on the sediment surface or buried in the sediment. From the experimental data and relationships of metabolic demand we calculated minimum resource requirement for maintenance (MRR) for each of the prey categories used in experiments. MRR increased with bream size for both zooplankton and visible chironomids, but decreased with bream size for buried chironomids, suggesting that intermediate sized bream (120-300 mm) may be competitively sandwiched between small and large bream that are more competitive planktivores and benthivores, respectively. Prey value estimates and competitive abilities qualitatively predicted diet shift in a bream population being released from competition. Competitive release did not change the diet of the largest size-class feeding on an optimal diet of benthic invertebrates both before and after competitive release. However, profound diet shifts towards benthic macro invertebrates were recorded for intermediate size-classes that fed on a suboptimal diet prior to competitive release. Thus, laboratory estimates of size-dependent foraging capacity of bream in planktivorous and benthivorous feeding niches provided useful information on size-specific competitive ability, and successfully predicted diet preference in the field.
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