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- Daly, Robert J., et al.
(författare)
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A palynological study of an extinct arctic ecosystem from the Palaeocene of Northern Alaska
- 2011
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 166:1-2, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- The Palaeocene arctic supported a vegetation type quite distinct from the tundra and polar desert of today. Here we demonstrate, through the palynological record, the structure of this extinct vegetation and its dynamics over this period. The Late Palaeocene coal-bearing units of the Sagwon Bluffs on Alaska's North Slope (present latitude 69 degrees N) are predominantly fine-grained, non-marine and rich in palynomorph-bearing sediments. From the analysed palynological assemblage we were able to demonstrate, using 'Detrended Correspondence Analysis' (DCA) and 'Fuzzy c-Means Cluster Analysis' (FCM), 1) a complex heterogeneous ecosystem, 2) its major successional states, and 3) its development over an extended period. The climax state of the floodplain was dominated by flood-tolerant, deciduous conifers such as Metasequoia. A more heterogeneous mid-successional assemblage is represented by angiosperm and gymnosperm co-dominance with an angiosperm dominance of Corylus, while early-successional ecological groups, dominated by ferns and bryophytes, are considered to represent riparian and post-disturbance niches. The structure of this vegetation does not remain static over the course of the stratigraphic interval represented. We observe a particularly dramatic ecological change for instance, following the deposition of a large conglomeratic unit. It is hypothesized that this corresponds to altered drainage and/or precipitation on the North Slope. The vegetation examined herein shows marked similarities to that of other palaeobotanical studies from various sites of similar age at high northern latitudes. It is hence considered to represent an extensive and long-lived circumpolar arctic biome. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Wood, Hannah L., 1980, et al.
(författare)
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Interaction of ocean acidification and temperature; the high cost of survival in the brittlestar Ophiura ophiura
- 2010
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 157:9, s. 2001-2013
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Tidskriftsartikel (refereegranskat)abstract
- This study has demonstrated an interaction between the effect of increased ocean acidity and temperature (40 days exposure) on a number of key physiological parameters in the ophiuroid brittlestar, Ophiura ophiura. Metabolic upregulation is seen in the low pH treatments when combined with low temperature. However, this is far outweighed by the response to elevated temperature (+4.5A degrees C). In the high temperature/low pH treatments treatments (where calcite is undersaturated) there appears to be an energetic trade-off likely in order to maintain net calcification where dissolution of calcium carbonate may occur. This energy deficit results in a similar to 30% reduction in the rate of arm regeneration at pH 7.3 which is predicted to be reached by the year 2300. This understanding of how O. ophiura responds to ocean acidification, taking into account an interactive effect of temperature, suggests that fitness and survival may indirectly be reduced through slower recovery from arm damage.
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| 3. |
- Wood, Hannah L., 1980, et al.
(författare)
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Ocean warming and acidification; implications for the Arctic brittlestar Ophiocten sericeum
- 2011
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 34:7, s. 1033-1044
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic Ocean currently has the highest global average pH. However, due to increasing atmospheric CO2 levels, it will become a region with one of the lowest global pH levels. In addition, Arctic waters will also increase in temperature as a result of global warming. These environmental changes can pose a significant threat for marine species, and in particular true Arctic species that are adapted to the historically cold and relatively stable abiotic conditions of the region. Consequently, we investigated some key physiological responses of brittlestar Ophiocten sericeum, a polar endemic which can dominate benthic infauna, to a temperature increase of 3.5°C (ambient, 5–8.5°C) and CO2 induced reduction in pH of 0.6 units (pH 7.7) and 1 unit (pH 7.3) below ambient (pH 8.3). Metabolism was upregulated at low pH. Faster arm regeneration stimulated by increased temperature was counteracted by low pH; at pH 7.3 in the high-temperature treatment, the maintenance of calcium carbonate structures in undersaturated conditions resulted in reduction in the rate of arm regeneration, possibly due to accelerated the use of energy reserves. If so, this could result in an energy deficit at times of increased energetic costs associated with responding to the combined factors of high temperature and low pH.
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