Home About us Contact
|
Home About us Contact | ||
|
|
||
Thermal Maximum (thermal + maximum)
Selected AbstractsA warm thermal enclave in the Late Pleistocene of the South-eastern United StatesBIOLOGICAL REVIEWS, Issue 2 2009Dale A. Russell ABSTRACT Physical and biological evidence supports the probable existence of an enclave of relatively warm climate located between the Southern Appalachian Mountains and the Atlantic Ocean in the United States during the Last Glacial Maximum. The region supported a mosaic of forest and prairie habitats inhabited by a "Floridian" ice-age biota. Plant and vertebrate remains suggest an ecological gradient towards Cape Hatteras (35°N) wherein forests tended to replace prairies, and browsing proboscideans tended to replace grazing proboscideans. Beyond 35°N, warm waters of the Gulf Stream were deflected towards the central Atlantic, and a cold-facies biota replaced "Floridian" biota on the Atlantic coastal plain. Because of niche diversity and relatively benign climate, biodiversity may have been greater in the south-eastern thermal enclave than in other unglaciated areas of North America. However, the impact of terminal Pleistocene megafaunal extinctions may also have been shorter and more severe in the enclave than further north. A comparison with biotic changes that occurred in North America approximately 55 million years (ma) ago at the Paleocene-Eocene Thermal Maximum suggests that similar processes of change took place under both ice-house and greenhouse climates. [source] Thermal tolerance and metabolic physiology among redband trout populations in south-eastern OregonJOURNAL OF FISH BIOLOGY, Issue 2 2004K. J. Rodnick Streamside measurements of critical thermal maxima (Tcrit), swimming performance (Ucrit), and routine (Rr) and maximum (Rmax) metabolic rates were performed on three populations of genetically distinct redband trout Oncorhynchus mykiss in the high-desert region of south-eastern Oregon. The Tcrit values (29·4 ± 0·1° C) for small (40,140 g) redband trout from the three streams, and large (400,1400 g) redband trout at Bridge Creek were not different, and were comparable to published values for other salmonids. At high water temperatures (24,28° C), large fish incurred higher metabolic costs and were more thermally sensitive than small fish. Ucrit(3·6 ± 0·1 LF s,1), Rr(200 ± 13 mg O2 kg,0·830 h,1) and metabolic power (533 ± 22 mg O2 kg,0·882 h,1) were not significantly different between populations of small redband trout at 24° C. Rmax and metabolic power, however, were higher than previous measurements for rainbow trout at these temperatures. Fish from Bridge Creek had a 30% lower minimum total cost of transport (Cmin), exhibited a lower refusal rate, and had smaller hearts than fish at 12-mile or Rock Creeks. In contrast, no differences in Ucrit or metabolism were observed between the two size classes of redband trout, although Cmin was significantly lower for large fish at all swimming speeds. Biochemical analyses revealed that fish from 12-mile Creek, which had the highest refusal rate (36%), were moderately hyperkalemic and had substantially lower circulating levels of free fatty acids, triglycerides and albumin. Aerobic and anaerobic enzyme activities in axial white muscle, however, were not different between populations, and morphological features were similar. Results of this study: 1) suggest that the physiological mechanisms that determine Tcrit in salmonids are highly conserved; 2) show that adult (large) redband trout are more susceptible to the negative affects of elevated temperatures than small redband trout; 3) demonstrate that swimming efficiency can vary considerably between redband trout populations; 4) suggest that metabolic energy stores correlate positively with swimming behaviour of redband trout at high water temperatures; 5) question the use of Tcrit for assessing physiological function and defining thermal habitat requirements of stream-dwelling salmonids like the redband trout. [source] Late-Quaternary palaeoclimatic research in Fennoscandia , A historical reviewBOREAS, Issue 4 2010H. JOHN B. BIRKS Birks, H. J. B. & Seppä, H. 2010: Late-Quaternary palaeoclimatic research in Fennoscandia , A historical review. Boreas, Vol. 39, pp. 655,673. 10.1111/j.1502-3885.2010.00160.x. ISSN 0300-9483. Ideas and understanding of Late-Quaternary climatic history, especially in the Lateglacial and the postglacial, were initiated in Fennoscandia in the 19th century with pioneering studies on peat stratigraphy, megafossils and macrofossils. This review traces the history of palaeoclimatic research and the development of current ideas about climatic changes, with particular reference to the Lateglacial and its rapid climatic fluctuations, such as the Younger Dryas period, and to the Holocene, with its thermal maximum and shifts in precipitation. [source] Late Quaternary history of the Kap Mackenzie area, northeast GreenlandBOREAS, Issue 3 2010BERND WAGNER Wagner, B., Bennike, O., Cremer, H. & Klug, M. 2010: Late Quaternary history of the Kap Mackenzie area, northeast Greenland. Boreas, Vol. 39, pp. 492,504. 10.1111/j.1502-3885.2010.00148.x. ISSN 0300-9483. The Kap Mackenzie area on the outer coast of northeast Greenland was glaciated during the last glacial stage, and pre-Holocene shell material was brought to the area. Dating of marine shells indicates that deglaciation occurred in the earliest Holocene, before 10 800 cal. a BP. The marine limit is around 53 m a.s.l. In the wake of the deglaciation, a glaciomarine fauna characterized the area, but after c. one millennium a more species-rich marine fauna took over. This fauna included Mytilus edulis and Mysella sovaliki, which do not live in the region at present; the latter is new to the Holocene fauna of northeast Greenland. The oldest M. edulis sample is dated to c. 9500 cal. a BP, which is the earliest date for the species from the region and indicates that the Holocene thermal maximum began earlier in the region than previously documented. This is supported by driftwood dated to c. 9650 cal. a BP, which is the earliest driftwood date so far from northeastern Greenland and implies that the coastal area was at least partly free of sea ice in summer. As indicated by former studies, the Storegga tsunami hit the Kap Mackenzie area at c. 8100 cal. a BP. Loon Lake, at 18 m a.s.l., was isolated from the sea at c. 6200 cal. a BP, which is distinctly later than expected from existing relative sea-level curves for the region. [source] | ||||||||||