Nutrient cycling in lakes

我的研究项目涉及微生物食物网和营养循环，在这个资助周期中，我的实验室将瞄准四个领域。 第一个领域涉及湖水中溶解有机磷（DOP）。 这是这种限制性营养素的最大溶解部分，但我们最近的工作表明，它主要是在样品制备的过滤步骤中获得的，可能是通过细胞破碎。 我们的假设是，真正溶解的有机磷也来自细胞破碎，但由于自然机制，如病毒裂解和放牧。 为了完成这一系列的研究，我们将测试的假设，DOP的高分子量部分主要是核酸，这些成为PO 4通过低分子量DOP，主要是核苷酸和其他底物可用于浮游生物通过细胞膜相关的磷酸酶。 第二条研究路线来自我们开发的放射性生物测定法，该测定法可以估计PO 4的浓度，PO 4是限制湖水中藻类生长的最重要的营养素。 我们将使用这种生物测定的经验和实验方法来测试假设的光和食物网的相互作用，在确定磷有限的湖泊中的PO 4浓度的作用。 我们的第三个重点将是整个湖泊的磷循环，我们将测试我们最近的文献综述TP和分层湖泊沉积的假设。 该假设是，P沉降增加异速生长与TP，使在一个中间（中营养）的范围内，湖泊抵抗TP浓度的增加，并在分层沉降TP向贫营养范围内的值。 最后，我们将把我们的一些努力，看看在磷有限的湖泊中的NH 4。 虽然实验证据表明，只有磷负荷可以增加这些湖泊的生物量，和N-循环得到了相对较少的关注，NH 4也在低浓度，难以测量，并迅速翻转。 它的浓度，沿着的PO 4，也是浮游植物的营养环境的一个重要决定因素，需要考虑到了解浮游生物的物种组成。

My research program concerns microbial food webs and nutrient cycles, and in this grant cycle my lab will target four areas. The first area concerns dissolved organic phosphorus (DOP) in lake water. This is the largest dissolved fraction of this limiting nutrient, but our recent work demonstrates that it is mostly derived during the filtration step of sample preparation, probably by cell breakage. Our hypothesis is that truly dissolved organic P is also derived from cell breakage, but due to natural mechanisms such as viral lysis and grazing. To complete this line of research we will test the hypotheses that the high molecular weight fraction of DOP is mostly nucleic acids, and that these become PO4 via low molecular weight DOP that is mostly nucleotides and other substrates available to plankton via cell-membrane associated phosphatases. The second line of research follows from our development of a radiobioassay that can estimate the concentration of PO4, the most important nutrient limiting the growth of algae in lake water. We will use this bioassay in both empirical and experimental approaches to test hypotheses concerning the role of light and food web interactions in determining the concentration of PO4 in P-limited lakes. Our third focus will be the whole-lake P cycle, where we will test a hypothesis arising from our recent review of the literature on TP and sedimentation in stratified lakes. The hypothesis is that P sedimentation increases allometrically with TP such that within an intermediate (mesotrophic) range, lakes resist increases in TP concentration, and during stratification sedimentation moves TP towards a value in the oligotrophic range. Finally, we will shift some of our effort to looking at NH4 in P-limited lakes. While experimental evidence suggests that only P-loading can increase the biomass of such lakes, and N-cycling has received relatively little attention, NH4 is also in low concentration, difficult to measure, and turning over rapidly. Its concentration, along with that of PO4, is also an important determinant of the nutrient environment of phytoplankton and needs to be considered to understand species composition of plankton.