Studies on the population dynamics and production of inshore marine copepods |
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| Authors: | Shin-ichi Uye |
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| Institution: | (1) Faculty of Applied Biological Science, Hiroshima University, Midori-machi 2-17, 720 Fukuyama |
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| Abstract: | It is indeed my great honor to receive the Okada Prize (1983) for my studies on the population dynamics and production of
inshore marine copepods. This article summarizes the lecture I gave under the above title.
It has long been postulated that there is some mechanism whereby a species can repopulate after its disappearance from the
plankton, since the appearance of many temperature marine copepods clearly occurs on a seasonal basis. During the last decade,
evidence of resting egg production has been found for more than 20 species belonging to Temoridae, Centropagidae, Pontellidae,
Acartiidae and Tortanidae. In the Inland Sea of Japan, a summer-fall copepodTortanus forcipatus lays diapause (obligatory resting) eggs in the fall, which overwinter in the sediment on the sea floor until the following
summer when water temperature reachesca. 15°C. On the other hand, in Onagawa Bay,Acartia clausi is perennial and produces only subitaneous eggs, many of which, however, sink to the bottom and undergo quiescence (facultative
resting eggs) due to adverse environmental conditions (e.g. low temperature, deoxygenation, darkness). There are a large quantity (0.5–2.0×106 eggs m−2) ofA. clausi resting eggs in the sediments of Onagawa Bay, which may play an important role in maintaining a more constant planktonic
population.
The parameters of population dynamics,i.e. the rates of egg production, recruitment and mortality, have been analyzed forA. clausi in Onagawa Bay, by an integration of field and laboratory studies. Recruitment into the planktonic population older than
NIII only accounts for 10–20% of egg production. This apparent loss of eggs, which coincides with the benthic resting phase,
may be a characteristic feature of the population dynamics of this species. Stage-specific mortality is generally similar
in most of the stages, although CI and CVI suffer more severe mortality, possibly as a result of great morphological change
in the former stage and heavy predations in the latter. The seasonal change in daily production byA. clausi has also been investigated, its annual production being 2.45 gC m−2. Daily production and biomass (P:B) ratios increase linearly with temperature. Estimated values of production for other inshore
marine copepods are reviewed in relation to P:B ratios and the ratio between secondary and primary production. |
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