MS Plan A Defense: An in-situ autonomous sampler system for vertical benthic biogeochemical fluxes detection

Jomphol Lamoonkit
Master’s Student
Department of Ocean and Resources Engineering
University of Hawai’i at Mānoa

**This defense will be held both in person (POST 723) and over Zoom**
Meeting ID: 958 6184 4769
Passcode: JomMS
https://hawaii.zoom.us/j/95861844769

Benthic environments in the coastal ocean, such as seagrass meadows, have gained attention for their capacity to store organic carbon in their tissues. Nevertheless, there is still room to study their influence on vertical biogeochemical fluxes between pore water beneath the sediment layer and the overlying seawater. The ability to monitor the vertical biogeochemical fluxes of seawater in the vegetated sedimentary environment could improve our understanding of the role of the vegetated benthic environment on the carbon cycle. Moreover, accurate and rapid measurement of benthic vertical biogeochemical fluxes could also contribute to the monitoring efforts for marine-based Carbon Dioxide Removal (mCDR) research in order to verify the subtle changes of seawater chemistry in the benthic regions.

This study aims to contribute to the biogeochemical monitoring efforts through an in-situ sampler system called the Benthic Alternating Autonomous Sampler (BAAS). The instrument is designed to be deployed on the seabed and to alternately sample between the sediment pore water and overlying water. The system is autonomously controlled by a microcontroller (Arduino). The design integrates Rhizon screen sections that allow retrieval of water samples from various sediment grain sizes (≥ 0.15 μm). In this study, optical pH and Oxygen sensors, and temperature probes are integrated, with possibilities to integrate other sensors into the system. A benchtop system is demonstrated in this study to explore the flow rate under different sediment types, carryover volume, alternation properties, and sensor readings, which would provide the critical basis for in-situ sensor development.

This in-situ sampler apparatus would enable us to study the effect of sediment types and sampling depth on the performance of the sampler. Furthermore, the open-source platform would facilitate other researchers’ ability to replicate the system easily. This sampler system would also open up possibilities for studying benthic sedimentary fluxes, providing insights into ocean ecosystems and seawater chemistry.