9:15 AM - 9:30 AM
[ACG40-02] Visualization of the extent of influence of volcanic fluids discharge from the seafloor in shallow coastal waters
Keywords:Submarine gas discharge, Visualization, CO2 seep, Shallow coastal waters
It is known that heat and/or material input from the seafloor, such as submarine groundwater discharge, exists in shallow coastal waters and affects shallow coastal ecosystems. On the other hand, such heat and/or material supply from the seafloor is spatially heterogeneous, and the extent of its influence is also heterogeneous, so that the spatial effects on coastal ecosystems are still unknown. It is important to visualize such heterogeneous fields in order to accurately understand the effects of heat and matter supply from the seafloor.
It has long been known locally that gases are emitted from the seafloor in the shallow coastal waters of Himeshima, Oita Prefecture. Several scientific investigations have been conducted and the gaseous components have been detailed to be volcanic fluids composed mainly of CO2 (e.g., Ohsawa and Mishima 2017, Ohsawa et al. 2022), but the spatial extent of their influence is still unclear.
Using the results of geophysical surveys and water quality observations, we developed a method to visualize the distribution characteristics of submarine groundwater discharge in shallow coastal waters in several regions. These results were presented at the 2018-2022 JpGU sessions. In this study, we attempt to visualize the extent of the impact of seafloor volcanic fluid discharge with reference to this visualization method.
The study was conducted in the coastal area of Nishiura fishing port at the western end of Himeshima, which is reported to have a significant discharge of volcanic fluids. To determine the spatial distribution, water quality (pH, temperature, salinity, turbidity, ORP, dissolved oxygen, and chlorophyll-a) was observed at multiple vertical and horizontal points and mapped in three dimensions. Significant decreases in pH, DO, and ORP were observed at several locations, confirming the existence of water quality differences within the target area and the formation of a spatially heterogeneous water quality field. On the other hand, there were no significant differences in salinity or temperature, and no obvious traces of groundwater inflow such as submarine groundwater discharge were observed. Visualization of the extent of the influence of seafloor volcanic fluid discharge and the actual conditions of the volcanic fluids are currently under analysis, and detailed results will be presented at the time of this presentation.
It has long been known locally that gases are emitted from the seafloor in the shallow coastal waters of Himeshima, Oita Prefecture. Several scientific investigations have been conducted and the gaseous components have been detailed to be volcanic fluids composed mainly of CO2 (e.g., Ohsawa and Mishima 2017, Ohsawa et al. 2022), but the spatial extent of their influence is still unclear.
Using the results of geophysical surveys and water quality observations, we developed a method to visualize the distribution characteristics of submarine groundwater discharge in shallow coastal waters in several regions. These results were presented at the 2018-2022 JpGU sessions. In this study, we attempt to visualize the extent of the impact of seafloor volcanic fluid discharge with reference to this visualization method.
The study was conducted in the coastal area of Nishiura fishing port at the western end of Himeshima, which is reported to have a significant discharge of volcanic fluids. To determine the spatial distribution, water quality (pH, temperature, salinity, turbidity, ORP, dissolved oxygen, and chlorophyll-a) was observed at multiple vertical and horizontal points and mapped in three dimensions. Significant decreases in pH, DO, and ORP were observed at several locations, confirming the existence of water quality differences within the target area and the formation of a spatially heterogeneous water quality field. On the other hand, there were no significant differences in salinity or temperature, and no obvious traces of groundwater inflow such as submarine groundwater discharge were observed. Visualization of the extent of the influence of seafloor volcanic fluid discharge and the actual conditions of the volcanic fluids are currently under analysis, and detailed results will be presented at the time of this presentation.