Apollonio S.,Arctic Institute of North America |
Saros J.E.,University of Maine, United States
Arctic | Year: 2013
Numbers, weights, and oxygen consumption of the copepod Limnocalanus macrurus were measured through the winter 1961-62 under the ice of Immerk Lake on Devon Island, Arctic Canada. Maximum abundance was 2361 animals per m3 found under ice in mid June, average adult wet weight was 65 μg, and hourly oxygen consumption per adult ranged from 0.26 μg in late summer to 0.03 μg in early winter. The results are compared with results from Char Lake and Resolute Lake on Cornwallis Island, Arctic Canada. The Immerk population was more stable than those at the other lakes, and weights and oxygen consumption appear to be comparable. The seasonal breeding cycle at Immerk Lake was different from that at Char Lake and similar to that at Resolute Lake. A comparison of Immerk Lake data from 1961-62 and 1972-73 showed almost identical levels of total oxygen metabolism. Immerk Lake copepod oxygen consumption was 6.5% of the total lake metabolism, while that at Char Lake was 6%. These data may assist in future assessment of climate or anthropogenic changes. © The Arctic Institute of North America.
Apollonio S.,Arctic Institute of North America |
Townsend D.W.,University of Maine, United States
Arctic | Year: 2011
Vertical profiles of temperature, salinity, dissolved oxygen, and inorganic nutrients (nitrate, phosphate, and silicate) were measured at five depths (2, 10, 25, 50, and 80 m) beneath the ice off the southern shore of Jones Sound, north of Devon Island, through the winter of 1961-62. Additional data were collected from the north side of the sound off Grise Fiord, Ellesmere Island, on 13 May 1962 and 12 May 1969. The over-winter data set is used here to characterize the transition of Arctic waters from autumn to late-spring-early summer. Minimum temperatures (< -1.8°C) and maximum salinities (> 33.2) were reached in late winter and early spring. Oxygen levels declined over the same fall-to-late-spring period and increased markedly in June. Nitrate, phosphate, and silicate concentrations all increased from their lowest values in fall to overall highest values in late spring, after which each nutrient showed evidence of biological uptake. A deep pycnocline, between 50 and 80 m, persisted from November to February, isolating a bottom-water layer that showed evidence of microbially mediated silicate regeneration (silicate concentrations increased, phosphate decreased, and nitrate concentrations were variable). In early spring (19 March to 1 May), nitrate concentrations dropped abruptly at all depths from more than 10 μM to less than 7 μM, apparently in response to the growth of ice algae. Temperature-salinity (T-S) analyses found little evidence of significant water-mass replacements during the study period, but interpretations of coherent variations in nutrient concentrations, as well as observed salinities slightly different from those expected on the basis of ice formation, suggest otherwise. Comparison of results from north of Devon Island with those from sampling off Grise Fiord in May 1962 indicate both higher salinities and lower nutrient concentrations at the latter site; however, data collected at the same site off Grise Fiord in May 1969 showed lower salinities and more variable nutrient concentrations than in 1962. © The Arctic Institute of North America.
Strong W.L.,Arctic Institute of North America
Forest Science | Year: 2015
Western North American lodgepole pine (Pinus contorta var. latifolia Engelmann ex S. Watson) relevés (n 6,918) were classified to identify regional difference in understory vegetation types. Seventy-nine types with > 5 relevés were recognized, but only 34 included > 40 relevés. Among the latter, shrubs dominated 15 types, excluding consideration of feathermosses. Buffaloberry (Shepherdia canadensis (L.) Nutt.), twinflower (Linnaea borealis L.), and bearberry (Arctostaphylos uva-ursi (L.) Spreng.) understory types spanned most of the latitudinal range. Eleven types occurred only north and four only south of 50o N latitude. Latitude explained 82% (P < 0.001, n 5,759) of the elevation variance among relevés, with a northward decline decreasing from 81 to 21 m/degree of latitude. A discontinuity in elevations at 50o N is thought to represent a northward shift from a cordilleran–prairie to a cordilleran– boreal ecoclimatic regime. A comparison of relevé and regression-predicted elevations identified 18 understory types that differed (P < 0.02) from the regional trend. May–August solar insolation, which was used as a proxy for latitudinal differences in slope gradient and orientation, indicated that 77% of P. contorta relevés were associated with more intensive solar insolation sites. When cross-referenced with elevation, 13 types differed from the norm in terms of both elevation and insolation. The results provide a framework for more detailed forest classification. © 2015 Society of American Foresters