Interactions Between Planktonic Community Structure and Nutrient Cycling Processes in Freshwater Ecosystems

研究水生生态系统浮游生物群落结构与养分循环之间的主要相互作用；特别是养分再生的地点和速率，包括氮和磷的比较。重复的池塘实验将在2X2矩阵中进行：添加或不添加鱼（以获得不同的浮游动物组合），以及施用高氮磷比或低氮磷比的肥料（以获得不同的浮游植物组合）。在这些群落结构下，养分再生机制的差异将被研究。将检验四个主要假设。(1)在以食用藻类和枝海类食草动物为主的浮游生物群落中，养分更新主要发生在水体中。(2)在以蓝藻为主的群落中，更大比例的养分再生将发生在沉积物中（如果死蓝藻下沉），或在蓝藻垫中（如果死蓝藻漂浮）。(3)在以不可食性真核藻类为主的群落中，或在具有较大的类calanoid桡足类成分的群落中，沉积物中发生更新的比例显著更高。(4)“微生物环”对营养物再生的相对重要性将随着浮游生物群落结构的变化而变化。结果不仅将检验这些关于水生群落如何运作的想法，而且将提供有价值的见解，这可能被证明对湖泊管理有用。

Major interactions between planktonic community structure and nutrient cycling in aquatic ecosystems will be researched; specifically the sites and rates of nutrient regeneration, including comparisons of nitrogen and phosphorus. Replicated pond experiments will be performed in a 2X2 matrix: fish added or not (to obtain different zooplankton assemblages), and ponds treated with fertilizer either with a high or low N:P ratio (to obtain different phytoplankton assemblages). Differences in the mechanisms of nutrient regeneration under these community structures will be examined. Four major hypotheses will be tested. (1) In plankton communities dominated by edible algae and cladoceran grazers, nutrient regeneration will occur principally in the water column. (2) In communities dominated by cyanobacteria, a significantly greater fraction of nutrient regeneration will occur in sediments (if dead cyanobacteria sink), or within the cyanobacterial mat (if dead cyanobacteria float). (3) In communities dominated by inedible eucaryotic algae, or in communities having a large calanoid copepod component, a significantly greater fraction of regeneration will occur in sediments. Finally, (4) the relative importance of the "microbial loop" to nutrient regenration will change as planktonic community structure changes. Results will not only test these ideas on how aquatic communities operate, but will provide valuable insight which may prove useful in lake management.