Denitrification within the Macroalgal Canopy in a Eutrophic Embayment

氮从沿海生态系统的损失， 反硝化作用被认为是氮的主要汇， 特别是在富营养环境中。本项目的重点 是覆盖在瓦科伊特底部的厚厚的大型海藻层 马萨诸塞州科德角的富营养化海湾。大型藻类的冠层 通常超过15厘米的厚度。在上三分之一的 由于密集的垫子，白天O2浓度很高， 光合作用和NH 4+浓度低（几μ M）。在 相比之下，树冠的下部即使在 日和NH 4+浓度非常高（数百μ M）。 因此，在距离藻类表面约5厘米的区域内， 条件是有利的硝化与足够的O2从 光合作用和扩散从上面和NH 4+扩散 下面据推测，高速率的反硝化作用可能 发生在藻类冠层内的高NH+4/低O2界面处， 在此过程中存在硝化-反硝化耦合 区假设的相互作用实际上是三重耦合， 光合-硝化-反硝化这一假设将 在一系列实验中进行检查， 位于马萨诸塞州伍兹霍尔的海洋生物实验室， 瓦阔特湾该项目将评估硝化作用， 在专门建造的室内进行脱氮， 沉积物、藻类冠层物质和上覆水。这些 问题直接涉及瓦阔特湾正在进行的工作， 目前正在调查的土地之一， 边缘生态系统研究计划（LMER）及其测量 获得的将是一个重要的输入到氮预算 这系统.

The loss of nitrogen from coastal ecosystems through denitrification is believed to be a major sink for nitrogen, particularly in eutrophic environments. The focus of this project is a thick macroalgal canopy that carpets the bottom of Waquoit Bay, a eutrophic embayment on Cape Cod, MA. The macroalgal canopy frequently exceeds a thickness of 15 cm. Within the upper third of the dense mat, O2 concentrations are high during the day due to photosynthesis and NH4+ concentrations are low (several uM). In contrast, the lower portion of the canopy is anaerobic even during the day and NH4+ concentrations are very high (hundreds of uM). Therefore, within a zone about 5 cm from the algal surface conditions are favorable for nitrification with sufficient O2 from photosynthesis and diffusion from above and NH4+ diffusing from below. It is hypothesized that high rates of denitrification may occur at the high NH+4/low O2 interface within the algal canopy due to the existence of denitrification-nitrification coupling in this zone. The hypothesized interaction is in fact a triple coupling of photosynthesis-nitrification-denitrification. This hypothesis will be examined in a series of experiments to be conducted at the Marine Biological Lab in Woods Hole, MA, a facility close by to Waquoit Bay. The project will evaluate nitrification and denitrification in specially constructed chambers containing sediment, algal canopy material, and overlying water. These questions relate directly to ongoing work at Waquoit Bay which is one of the current sites under investigation through the Land Margin Ecosystem Research Program (LMER) and the measurements obtained will be an important input into the nitrogen budget of this system.