By OCAdmin in 演講公告 on

講者：Prof. Jotaro Urabe (Tohoku University, Japan)

題目：Stoichiometry of assimilation in zooplankton for growth maximization: eat more or eat less?

時間：Oct. 27 (Fri) 3:30-5:00pm

地點：海洋所2樓大講堂

摘要：
A theory of ecological stoichiometry suggest that herbivore plankton such as Daphnia should suffer from P deficiency in lakes where C:P atomic ratio of seston (phytoplankton) is higher than 300 . However, in nature, their growth rates are not necessarily relate with seston C:P ratios. This paradoxical situation may occur due to complex feeding and assimilation responses of herbivores to given diets. To examine such possibilities, we measured feeding and assimilation rates of Daphnia, one of common herbivore plankton in lakes, using various mono- and mixed algal diets under a constant diet level (1mg C/L), and examined how these rates were related with the growth rate. Depending on algal species and their mixtures, C:P ratio of the diets varied from 120-700. As expected, Daphnia growth rates poorly related with diet C:P ratios (r=0.33). However, it related well with feeding rates for P (r=0.66) and highly with assimilation rates for P (r=0.85). The results indicate that Daphnia growth rates do not necessarily relate with elemental contents in the food since the feeding performance and assimilation efficiencies change depending on species and elemental compositions of algal diets. Based on these experimental results, I will argue from the view point of ecological stoichiometry whether herbivore plankton should eat more or less for maximizing their growth rate when nutritionally poor foods are supplies.