RUI: The Importance of Clays and Dissolved Organic Matter to the Trophic Base of Turbid Lake Ecosystems

粘土浑浊抑制了湖泊浮游植物的产生。这项研究将调查粘土在另一条营养途径中的补偿作用。据推测，溶解有机质(DOM)通过在粘土颗粒上的聚集更容易被更高的营养水平所利用。具体地说：(1)粘土颗粒吸附了大量的DOM(其营养价值因来源而异)，以促进细菌的产生；以及(2)由于细菌的表面生长，吸附了DOM的粘土颗粒聚集成更大的颗粒。这项研究将研究自养和异养的相对重要性，以及粘土颗粒在湖泊食物网中发挥重要作用的机制。该项目回答了四个问题：(1)粘土浊度是否影响细菌产量和浮游植物产量的绝对量和相对量？(2)粘土浊度是否影响浮游植物渗出物的细菌利用？(3)粘土的吸附或聚集能力是否因DOM的性质而异((4)细菌在集合体上的生长是否影响粘土-有机-细菌集合体的大小？查帕拉湖可预测的悬浮粘土浓度的空间和时间梯度允许实验室和现场实验相结合来检验假设。答案将允许适用于粘土浊度较高的湖泊和水库的新营养模型。管理者或许能够取代基于传统模式的管理做法(水质和渔业)。这种替代途径在热带湖泊中尤其重要，因为常年温暖的水域能够保持持续的高细菌活动。这个项目是在瑞倡议下资助的。它的独特之处在于它让本科生参与到热带地区的实地工作中，并通过使用国际合作者。

Clay turbidity inhibits the phytoplankton production of lakes. This research will investigate a compensatory role for clays in an alternate trophic pathway. It is hypothesized that dissolved organic matter (DOM) is more available to higher trophic levels through concentration on clay particles. Specifically: (1) clay particles adsorb significant quantities of DOM (the nutritional value of which varies with the source) to facilitate bacterial production; and (2) as a result of bacterial surface growth, clay particles with adsorbed DOM aggregate into larger particles. The research will examine the relative importance of autotrophy and heterotrophy, and the mechanisms by which clay particles are important in lake food webs. The project answers four questions: (1) Does the quantity of clay turbidity affect the absolute as well as the relative amounts of bacterial production and phytoplankton production? (2) Does the quantity of clay turbidity affect bacterial use of phytoplankton exudates? (3) Does the sorptive or aggregative capacity of the clays vary with the nature of the DOM (allochthonous vs. autochthonous)? (4) Does bacterial growth on aggregates affect the size of the clay-organic-bacteria aggregates? Lake Chapala's predictable spatial and temporal gradients of suspended clay concentrations allows a combination of laboratory and field experimentation to test hypotheses. Answers will permit a new trophic model appropriate to lakes and reservoirs with high clay turbidity. Managers may be able to replace management practices (water quality and fisheries) based on traditional models. This alternate pathway is especially important in tropical lakes because year-around warm waters enable consistently high bacterial activity. This project is funded under the RUI initiative. It is unique in its involvement of undergraduates in field work in the tropics and through its use of international collaborators.