Interaction Effects of Solar Ultraviolet Radiation and the Nutrient Environment on the Dynamics of Growth of Freshwater Bacteria and Phytoplankton

暴露于太阳紫外线辐射（UVR）是生活在水生环境透光层的生物的生活事实。浮游动物、浮游植物、原生动物和浮游细菌对UVR暴露的生理和行为反应具有明显的类群差异。尽管营养盐的竞争被认为是构建浮游生物群落组成的关键因素，但在自然条件下，UVR对浮游生物之间限制矿物营养盐的竞争强度的重要性尚不清楚。拟议的研究将有助于填补这一知识空白。我们将研究营养盐和UVR制度对自然发生的浮游植物和浮游细菌的生长速率和对磷的竞争的主要影响和相互作用。本文提出了一个模型，并对不同营养盐（有机碳和磷）比例和紫外线照射条件下营养盐竞争的严重程度进行了预测，我们预测，由于紫外线照射对浮游植物和浮游细菌生长速率的不同影响，紫外线照射将改变浮游植物和浮游细菌对磷竞争的严重程度。利用从北密西西比低海拔水库采集的样本，将进行实验来检验模型的预测。这项研究满足了两个需求。这将是第一个通过实验使用自然阳光的相互作用的影响，紫外线辐射和营养制度对生长速率的自养和异养浮游生物在不同程度的营养限制。第二，它将提供知识的影响，紫外线辐射制度的相对重要性的自养和细菌异养生产在美国南部的水生生态系统，在那里，与高纬度相比，there has been very little research研究on the ecological生态significance意义of UVR紫外线.学生将参与项目的所有方面，从计划到采样，数据分析到演示。由于臭氧层的破坏，温带地区的UVR预计将持续增加，UVR对浮游生物营养层关系的影响构成了一个及时和重要的问题。

Exposure to solar ultraviolet radiation (UVR) is a fact of life for organisms living inthe photic zone of aquatic environments. It is increasingly evident that zooplankton,phytoplankton, protozoa, and bacterioplankton exhibit taxon-specific differences inphysiological and behavioral responses to UVR exposure. Although competition fornutrients is recognized as a critical factor in structuring plankton communitycomposition, nothing is known of the significance of UVR under natural conditions for theintensity of competition among plankton for limiting mineral nutrients. The proposedresearch will help to fill this gap in knowledge. We will examine the main andinteraction effects of the nutrient and UVR regime on the growth rates and competition forphosphorus of naturally occurring phytoplankton and bacterioplankton. A model ispresented and predictions made regarding the severity of nutrient competition under arange in conditions of nutrient (organic carbon and phosphorus) ratios and UVR exposure.We predict that, because of differential effects on bacterioplankton and phytoplanktongrowth rates, UVR will modify the severity of competition between phytoplankton andbacterioplankton for phosphorus. Using samples collected from a low-altitude reservoir innorth Mississippi, experiments will be conducted to test the model predictions. Thisstudy fulfills two needs. It will be the first to evaluate by experimentation usingnatural sunlight the interaction effects of UVR and the nutrient regime on growth rates ofautotrophic and heterotrophic plankton under various degrees of nutrient limitation.Second, it will provide knowledge of the influence of the UVR regime on the relativeimportance of autotrophic and bacterial heterotrophic production in a southern U.S.aquatic ecosystem, where, compared to higher latitudes, there has been very littleresearch on the ecological significance of UVR. Students will be involved in all aspectsof the project, from planning to sampling to data analysis to presentation. Withanticipated continued increases of UVR in temperate regions due to ozone depletion, theeffect of UVR on plankton trophic-level relationships constitutes a timely and importantproblem.