PRF/J: Effects of Geothermal Phosphorus Inputs on Microbes, Litter, Decomposition, and Higher Trophic Levels in a Tropical Stream

9403292罗斯蒙德尽管水生食物网中的营养物质可以控制初级生产者的生长速度(由较高的营养水平消耗)，但很少有研究直接探讨营养物质在碎屑系统中的作用。中美洲的景观规模的火山活动导致了地表水化学的显著变化，包括可溶性活性磷(P)浓度的急剧增加，对河流生物群产生了明显的局部影响。这项研究将研究地热磷的输入是否会增加微生物生物量、养分含量和落叶分解速率。磷的变化对较高营养水平的影响将通过比较漂流密度和诱捕密度以及有害食性虾的大小来评估。高磷和低磷地点的叶凋落物质量的比较将使用有害的生长和脂肪含量的衡量标准。微生物和大消费过程在叶片分解中的相对重要性将通过对营养水平的原位操纵来确定。自下而上(营养)控制和自上而下(有害)控制都将被研究。碎屑在营养动态中的作用还没有得到很好的研究，尤其是在流水生态系统中。但除了基础研究方面，这个项目的重要性源于我们需要了解水生系统是如何运行的，因为人口压力给美国、拉丁美洲和世界各地的自然环境带来了越来越大的负担。***

9403292 Rosemond Although nutrients in aquatic food webs may control growth rates of primary producers (which are consumed by higher trophic levels), few investigations have directly probed the role of nutrients in detrital systems. Landscape - scale volcanic activity in Central America results in prominent changes to surface water chemistry, including dramatic increases in soluble reactive phosphorus (P) concentrations, with appreciable localized effects on stream biota. This research will examine whether geothermal P inputs enhance microbial biomass, nutrient content, and leaf litter decomposition rates. Effects of P variation on higher trophic levels will be assessed by comparing drift and trap densities, and size of detritivorous shrimp. High and low P site comparisons of leaf litter quality will be performed using measures of detritivore growth and fat content. The relative importance of microbial versus macroconsumer processes in leaf decomposition will be determined using in situ manipulations of nutrient levels. Both bottom - up (nutrient) control and top - down (detritivory) control will be examined. %%% The role of detritus in trophic dynamics hasn't been well studied, particularly in lotic (flowing water) ecosystems. But beyond fundamental research aspects, this project's importance derives our need to know how aquatic systems operate, as human population pressures place increasing burdens on the natural environment, in the United States, Latin America, and around the world. ***