Title of Project:
2023 Seafloor Mapping and Seabed Characteristics Investigation

Duration:
April 1, 2023 to March 31, 2024

Name of Principle Investigator:
Ho-Han Hsu, Associate Professor, Project PI, Institute of Oceanography, National Taiwan University
Chih-Chieh Su, Associate Professor, Project Co-PI, Institute of Oceanography, National Taiwan University
Char-Shine Liu, Research Fellow and Chief Executive Officer, Project Co-PI, Ocean Center, National Taiwan University

Abstract of Project:
This project aims to collect bathymetric and seabed data in our territorial sea, internal waters, and economic exclusion zone where the data is lacking or unreliable in the offshore area of Taiwan. In addition, three major tasks, namely, "seabed topography mapping", "seabed characteristics investigating" and "Taiping Island water quality testing" were carried out in response to the needs of the electronic navigational chart mapping. The research vessel LGD-2306 conducted multibeam bathymetric surveys, collected and analyzed seabed surface sediments and water samples from Taiping Island to understand the seabed topography and seafloor of the survey area, as well as the characteristics of the water resources surrounding the Zhenghe Group of reefs in the
 
South China Sea. During the cruise, we completed 1,164 nautical miles of main survey lines and 125 nautical miles of check lines around the Spratly Islands, covering an area of about 5,500 square kilometers. Additionally, we collected data from 75 stations of sound velocity profiling, about 1,430 nautical miles of seafloor imagery, and substrate profiling with the bathymetric surveys. Furthermore, 5 stations of seafloor sediment sampling, 15 temperature and salinity pressure measurements, and 37 seawater samples collecting are completed. When the R/V docked at Taiping Island, we successfully obtained 5 seawater samples, 1 set of temperature and salinity pressure records, and analyzed the water quality of 4 wells on the island.

Figure 1: Results of seabed topographic mapping in the survey area. The scope of bathymetric data collected in the survey area of this project mainly includes the waters around Tizard Bank, most of the surveyed areas are the first time to obtain bathymetric mapping data.

Figure 2: Results of the seabed topographic mapping of the waterways around Taiping Island and inside the Tizard Bank. This program focuses on the completion of high- resolution topographic mapping of the channel around Taiping Island and the inside of the Tizard Bank near the inner side of Taiping Island.

Figure 3: Results of sound velocity profile measurements at 75 stations during the cruise. Among them, except for one station where the XBT instrument malfunctioned, a total of five measurements were conducted using XBT-T7/T5/T10, XCTD, and CTD.

Figure 4: Preliminary results of temperature and salinity pressure measurements around the Tizard Bank. Submarine groundwater signals from the Tizard Bank were detected in the waters around Taiping Island.

Figure 5: This project integrates the results of temperature and salinity pressure measurements over the past 10 years. We found that the hydrographic properties of the South China Sea have oscillated significantly over the past 10 years, and the cause of this oscillation needs to be further clarified.