Denitrification measurements of sediments using cores and chambers: comparison of fluxes and denitrification efficiencies

Denitrification is a microbial process that takes place on and within sediment and results in the transformation of dissolved inorganic nitrogen to nitrogen gas (N2), which is subsequently lost to the atmosphere. In coastal waters denitrification is an important pathway for the removal of excess nitrogen. Rates of denitrification are typically quantified using either in situ benthic chambers or sediment cores incubated in the laboratory. This study assesses if these two approaches give similar fluxes and denitrification efficiencies. This dataset gives fluxes of: i) dissolved oxygen (DO); ii) nitrogen gas (N2); iii) dissolved inorganic nitrogen (DIN); iv) nitrate (NO3-); v); nitrite (NO2-) and vi) ammonium (NH4+) between the sediment and the water column. Results are obtained using core cylinders incubated in the laboratory and in situ benthic chambers. Fluxes are expressed as µmol m-2 of seafloor surface day-1. Denitrification efficiency is also reported and represents the flux of N2 as a proportion of the total flux of DIN. Studies were carried out in Port Phillip Bay at Clifton Springs and Williamstown, Victoria in March and May 2004, respectively. The flux of oxygen, ammonium, nitrate, nitrite and the denitrification efficiency was found to differ between in situ benthic chambers and laboratory incubated sediment cores. Additional experiments were conducted to assess if the abundance of macrofauna in sediments of core cylinders and benthic chambers differed; and ii) if physical disturbance associated with the collection and transport of core cylinders could account for the observed differences.

反硝化作用（Denitrification）是一种发生于沉积物表层及内部的微生物过程，可将溶解性无机氮转化为氮气（N₂），随后释放至大气中。在近岸海域中，反硝化作用是移除过量氮素的重要途径。反硝化速率通常通过两种方式量化：一是原位底栖腔室（in situ benthic chambers），二是实验室培养的沉积物岩芯（sediment cores）。本研究旨在评估这两种方法所测得的通量与反硝化效率是否一致。本数据集包含沉积物与水柱之间的以下物质通量：i）溶解氧（DO）；ii）氮气（N₂）；iii）溶解性无机氮（DIN）；iv）硝酸盐（NO₃⁻）；v）亚硝酸盐（NO₂⁻）；以及vi）铵态氮（NH₄⁺）。所有实验结果均通过实验室培养的沉积物岩芯与原位底栖腔室测得。通量单位为微摩尔每平方米海底每日（µmol·m⁻²·d⁻¹）。本数据集同时提供反硝化效率数据，其定义为氮气（N₂）通量占溶解性无机氮（DIN）总通量的比例。研究分别于2004年3月与5月，在澳大利亚维多利亚州菲利普港湾（Port Phillip Bay）的克利夫顿斯普林斯（Clifton Springs）与威廉斯敦（Williamstown）开展。研究发现，原位底栖腔室与实验室培养沉积物岩芯所测得的溶解氧、铵态氮、硝酸盐、亚硝酸盐通量以及反硝化效率均存在显著差异。本研究还开展了额外实验，以评估两个问题：一是沉积物岩芯柱样与底栖腔室中沉积物的大型底栖生物（macrofauna）丰度是否存在差异；二是沉积物岩芯柱样采集与运输过程中伴随的物理扰动是否能够解释上述观测到的差异。