Phosphate measurements at lander_1 in a coastal peatland at the German Baltic Sea in 2021

Rewetting peatlands is an important measure to reduce greenhouse gas (GHG) emissions. However, after rewetting, the areas are highly heterogeneous in terms of GHG exchange, which depends on water level and source, vegetation, previous use, and duration of rewetting. These challenging conditions require new technologies that go beyond discrete sampling. Here we present data from two autonomous lander platforms deployed at the sediment-water interface (bottom lander) of a shallow coastal peatland (approx. 1 m water depth) that was rewetted by brackish water from the Baltic Sea, thus becoming part of the coastal water through a permanent connection. These landers were equipped with six commercially available state-of-the-art sensors, and temporal high-resolution measurements of physico-chemical variables, including partial pressures of carbon dioxide (CO2) and methane (CH4), were made. The resolution of the field data ranged from 10 seconds to 120 minutes and was obtained for partial pressure of CO2 (Contros HydroC-CO2) and CH4 (Contros HydroC-CH4), temperature, salinity, pressure (water depth), oxygen (O2) (CTD-O2 with SBE-37SMP-ODO), the concentrations of phosphate (SBE HydroCycle PO4), nitrate (SBE SUNA V2), chlorophyll a and the turbidity (both with SBE-FLNTUSB ECO) as stationary measurements at two different locations in close proximity. The CTD and oxygen measurements provide exact water depth data for the respective lander locations. In the other data sets (e.g., CO2 measurements) rounded data are inserted instead of the exact depth data, which is 0.6 m for lander_1 and 0.9 m for lander_2. SUNA raw data are provided for completeness. However, we found them of insufficient quality to estimate nitrate concentrations due to interferences and biofouling. The deployment and recovery of the landers, and thus the measurements, took place between 02 June 2021 and 09 August 2021, and the sensors were operated under permanent wired power supply and a centralized timestamp. The sensors were maintained and cleaned bi-weekly. Results show considerable temporal fluctuations expressed as multi-day, diurnal, and event-based variability, with spatial differences caused by biologically-dominated variables.

泥炭地复湿是减少温室气体（GHG）排放的重要措施。然而，复湿后区域内的温室气体交换具有高度异质性，这取决于水位与水源、植被、既往用途及复湿持续时间。这些复杂条件需要超越离散采样的新技术。本文呈现了两个自主着陆平台的数据，这些平台部署于某浅海泥炭地（水深约1米）的沉积物-水界面（sediment-water interface）处——该泥炭地通过波罗的海微咸水复湿，且经永久连接成为沿海水域的一部分。这些着陆器配备了六个商用最先进传感器，对包括二氧化碳（CO2）和甲烷（CH4）分压在内的理化变量进行了时间高分辨率测量。实地数据的分辨率介于10秒至120分钟之间，测量内容包括CO2分压（Contros HydroC-CO2）、CH4分压（Contros HydroC-CH4）、温度、盐度、压力（水深）、氧气（O2，CTD-O2搭配SBE-37SMP-ODO传感器）、磷酸盐浓度（SBE HydroCycle PO4）、硝酸盐浓度（SBE SUNA V2）、叶绿素a及浊度（两者均使用SBE-FLNTUSB ECO传感器），所有测量均为邻近两个不同位置的固定观测。CTD与氧气测量为各着陆器位置提供了精确的水深数据。在其他数据集（如CO2测量数据）中，使用四舍五入数据替代精确水深数据——lander_1的水深为0.6米，lander_2为0.9米。为保证完整性，本文提供了SUNA原始数据；但由于干扰与生物污损，其质量不足以用于估算硝酸盐浓度。着陆器的部署与回收（即测量时段）为2021年6月2日至8月9日，传感器采用永久有线供电及集中时间戳运行。传感器每两周维护清洁一次。结果显示显著的时间波动，表现为多日、昼夜及事件驱动的变化，空间差异则由生物主导变量引起。