Plankton Regulation Dynamics Experiments and Models in Rotifer Conti
Continuous cultures, i.e. chemostats with an continuous dilution rate, are model ecosystems for the study of general regulation principles in plankton communities. Further to an introduction, general continuous culture methods and especially the character
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The different continuous culture techniques described in this volume offer - in various steps of complexity and technical investments - a world of new aspects both for experimental and on theoretical ecology. This concerns such broad fields as population and community ecology, ecosystem theory, ecotoxicology, and aquaculture. For the application of continuous cultures to these fields, many preparations and prerequisites have been necessary. For example, the mathematically well-formulated chemostat theory worked out for microorganisms had to be modified for metazoans (Chap. 3.3). Semicontinuous cultures have been developed (Chap. 2.1) as a method well suited to give excellent support to work on questions of the growth characteristics of populations (Chap. 3.1). Another possibility involves studying competition between populations within the community by means of resource partitioning (Sect. 6.2.5) or by "shift-up" and "shift-down" experiments (Chap. 6.1). Another application is in ecotoxicology (Chap. 7.3). This method is in the best sense very simple and at a low technical level, so it may be applied in many laboratories. The characteristic dilution of the system is done mechanically by a regular discard of a fixed part of the culture volume supplemented with a new feed suspension. The manpower requirement, on the other hand, seems to be fairly high. In particular, the working hours needed could restrain this method. Fed-batch cultures (Sect. 2.1.2 may be particularly adapted to experiments on zooplankton population dynamics. The first method has been utilized with rotifers, but nothing speaks against the successful application of both lines to cladocerans and protozoans. In contrast, the turbidostat is the technically highest developed continuous culture device (Chap. 2.3). Its operation field includes studying the maximum performances of physiological and population dynamic parameters and selecting the fittest popUlations (Chap. 3.4). Maximum performances (e.g., rmax) are affected the most by toxins. This technique, therefore, should be well suited for the assessment of ecotoxicity (Sect. 7.3.8) as a system response. Hitherto, this kind of turbidostat has not been used in aquaculture, for which it should be a very interesting method. The effort to build up and operate chemostats is shared between both parts. This technique is nearly as time consuming as semicontinuous cultures, while
N. Walz (ed.), Plankton Regulation Dynamics © Springer-Verlag Berlin Heidelberg 1993
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N. Walz
the methodical investment may be a little lower than that for turbidostats (Chap. 2.2). Because of its more constant dilution rate, it supplies more evident results. Because of its substrate limitation, it imitates best the situation in the community and in the ecosystem. The chemostat, therefore, is mostly adapted as a model ecosystem both in its single and two-stage version. This system has been successfully used to study the carbon metabolism and energy balance of different rotifer species (Part 4). This method was applied
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