Population and Production Ecology of Zooplankton in Ogac Lake, a Landlocked Fiord on Baffin Island
Collections were analysed from the three basins of the lake in 1957, and from the middle basin of the lake and a fertilized polyethylene column in 1962. The abundant copepod, Pseudocalanus minutus, was basically annual in life cycle, spawning a number of almost synchronous broods (egg sacs) in the s...
| Published in: | Journal of the Fisheries Research Board of Canada |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Canadian Science Publishing
1969
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/f69-139 http://www.nrcresearchpress.com/doi/pdf/10.1139/f69-139 |
| Summary: | Collections were analysed from the three basins of the lake in 1957, and from the middle basin of the lake and a fertilized polyethylene column in 1962. The abundant copepod, Pseudocalanus minutus, was basically annual in life cycle, spawning a number of almost synchronous broods (egg sacs) in the short period of abundant food supply in early summer. The number of young per brood was dependent on size of females, and the number of broods was independent of the amount of food during the reproductive season. The species was concentrated in rich food supply at the halocline and at depth. There was no diurnal vertical migration in summer, but ontogenetic descent of older stages appeared adapted to "seeking" colder water. The species is much smaller in the lake than in the nearby sea, and this, as well as seasonal size changes, can be attributed to temperature effects. Females, but not males, roughly doubled weight ("Brooks' Law") between stages in constant conditions. Maximum development rate was about 0.4 stages/day at 6–7 C, similar to laboratory estimates reported for temperate populations. Growth is not isometric; P. minutus grows stouter as it grows longer. Net production (some 30% as eggs) ranged from 410 to 510 mg C/m 2 per year in various basins and years, and was less than doubled in the fertilization experiment.The copepod Oithona similis was strictly annual and produced almost synchronous broods (two egg sacs), which were successfully recruited only in late summer, on different food requirements from those of P. minutus. It was nonmigratory in summer, and its vertical distribution, like its size, was little influenced by temperature. Weight increments were only about 50% between copepodite stages, and development between egg and adult took at least 1.2–1.6 months. Production ranged from 202 to 347 mg C/m 2 per year and was not increased in the fertilization experiment.The chaetognath Sagitta elegans was annual in the lake, reaching full size but suspending development during summer. Much reproduction ... |
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