Experimental Evaluation of Microbial Biomass and Production in Limnetic Food Webs Dominated by Planktivorous Fish

这项研究将确定微生物的生物量和产量（细菌、直径小于5微米的藻类和原生动物）如何对浮游鱼类带来的剩余的沼泽食物网的变化做出反应。实验将在18个大型室外水箱中进行，以比较三种浮游鱼类（多罗索马、金氏罗非鱼和绿柱头鱼）对浮游食物网的微生物和其他组成部分的影响。由于这些鱼类对浮游动物和浮游植物具有不同的选择性，我们预计微生物生物量和产量的间接响应，以及微生物生产向其他食物网组成部分的转移。实验将在不同的季节进行，以比较鱼类对浮游生物群落的影响，代表不同的天气状况。在每次水箱实验中，将通过测量原生动物和后生动物浮游生物对放射性同位素标记的细菌和藻类的摄取量来确定原生动物对细菌和藻类的摄取率，以及后生动物浮游动物对细菌、藻类和原生动物的摄取率。浮游鱼类对原生动物的放牧影响将在与每个水箱实验相关的短期喂养试验中进行测量。这些实验为确定微生物环在浮游食物网中的作用提供了一种综合实验方法。

This research will determine how microbial biomass and production (bacteria, algae less than 5 um in diameter, and protozoa) respond to changes in the remainder of the limnetic food web brought about by planktivorous fish. Experiments will be conducted in 18 large outdoor tanks to compare the effects of three planktivorous fish (Dorosoma cepedianum, Tilapia aurea and Menidia beryllina) on microbial and other components of the limnetic food web. Because these fish have different selectivities on zooplankton and phytoplankton, we expect significant indirect responses of microbial biomass and production, and in the transfer of microbial production to other food web components. Experiments will be conducted in different seasons to compare fish effects on plankton communities representative of different weather regimes. During each tank experiment, grazing rates of protozoa on bacteria and algae, and grazing rates of metazoan zooplankton on bacteria, algae, and protozoawill be determined by measuring ingestion of radioisotope-labelled bacteria and algae by protozoa and metazoan plankton. The grazing impact of planktivorous fish on protozoa will be measured in short-term feeding trials associated with each tank experiment. These experiments provide an integrated experimental approach to the determination of the role of the microbial loop in planktonic food webs.