Growth of juvenileArctica islandica under experimental conditions |
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Authors: | R Witbaard R Franken B Visser |
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Institution: | (1) Netherlands Institute for Sea Research, PO Box 59, 1790 AB Den Burg, The Netherlands |
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Abstract: | In two laboratory experiments, the effects of temperature and food availability on the growth of 10- to 23-mm high specimens
of the bivalveArctica islandica were estimated. Each experimental set-up consisted of 5 treatments in which either the food supply or the temperature differed.
It was demonstrated thatArctica is able to grow at temperatures as low as 1°C. A tenfold increase of shell growth was observed at temperatures between 1°
and 12°C. The greatest change in growth rate took place between 1° and 6°C. Average instantaneous shell growth varies between
0.0003 at 1°C to 0.0032/day at 12°C. The results suggest that temperature hardly affects the time spent in filtration, whereas
particle density strongly influences that response. Starved animals at 9°C have their siphons open during only 12% of the
time, whereas the siphons of optimally fed animals were open on average during 76% of the observations. Increased siphon activity
corresponded to high shell and tissue growth. At 9°C, average shell growth at the optimum cell density of 20×106 cell/l was 3.1 mm corresponding to an instantaneous rate of 0.0026/day. An algal cell density (Isochrysis galbana, Dunaliella marina) ranging between 5 and 7×106 cell/l is just enough to keep shells alive at 9°C. Carbon conversion efficiency at 9°C is estimated to vary between 11 and
14%. |
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