Do Top-Down and Bottom-Up Controls Interact to Exclude N-Fixing Cyanobacteria From the Plankton of Estuaries?

作者：rwh2@cornell.edu （Robert W. Howarth）在注日期：1996年3月26日12:08 PM优先级：正常到：cdahm在nsf2 CC: rmm3@cornell.edu在注CC: 73753.2331@compuserve.com在注主题：DEB 9527405摘要-------------------------------消息内容------------------------------- Hi Cliff—这是我对您要求的摘要的尝试。迈克·佩斯和我还在研究预算。Bob DEB-95-27405：“自上而下和自下而上的控制是否相互作用，以排除河口浮游生物中的固氮蓝藻？”富营养化和浮游植物的生产经常受到河口氮和湖泊磷的限制。造成这种显著差异的一个原因是固氮的不同。在湖泊中，当氮的可用性较低时，固氮生物会大量繁殖，并通过将分子氮固定为生物可用的形式来帮助缓解氮的不足。在大多数河口，没有这样的反应发生。这一提议验证了一个假设，即河口中微量金属（铁和钼）相对于湖泊的低可利用性导致固氮生物的生长速度缓慢，使这些生物容易被动物消耗，从而阻碍了固氮。在用装满海水的水箱进行的初步实验中，研究人员通过降低动物数量，成功地培养出了固氮生物。这是第一次在北美任何地方的河口水域中发现湖泊中常见的固氮生物。新的研究将建立在这些水箱研究的基础上，以更全面地测试湖泊和河口之间的假设差异。

Author: rwh2@cornell.edu (Robert W. Howarth) at NOTE Date: 3/26/96 12:08 PM Priority: Normal TO: cdahm at nsf2 CC: rmm3@cornell.edu at NOTE CC: 73753.2331@compuserve.com at NOTE Subject: Abstract for DEB 9527405 ------------------------------- Message Contents ------------------------------- Hi Cliff -- Here is my stab at the abstract you requested. Mike Pace and I are still working on the budget. Bob DEB-95-27405: "Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries?" Eutrophication and phytoplankton production are frequently limited by nitrogen in estuaries and by phosphorus in lakes. One reason for this striking differences is a difference in nitrogen fixation. In lakes when nitrogen availability is low, nitrogen-fixing organisms bloom and help alleviate the nitrogen deficit by fixing molecular nitrogen into biologically available forms. In most estuaries, no such response occurs. This proposal tests the hypothesis that low availabilities of trace metals (Fe and Mo) in estuaries relative to lakes leads to slow growth rates of nitrogen-fixing organisms, leaving these organisms vulnerable to consumption by animals, and thereby preventing nitrogen fixation. In preliminary experiments with tanks full of seawater, the investigators successfully grew nitrogen fixing organisms by keeping animal populations low. This was the first time nitrogen-fixing organisms of the sort common to lakes were found in estuarine water anywhere in North America. The new research will build on these tank studies to more completely test the hypothesized difference between lakes and estuaries.