Characteristic analysis of White hydrothermal vent in the southeastern Kueishantao Islet off Taiwan Island

Investigation into seafloor hydrothermal activity and its surroundings has been one key point of studying ocean sciences. Physical and chemical parameters obtained from the hydrothermal environments would be influenced by the tide, especially from the shallow hydrothermal vent. It is distributing many hydrothermal vents on the less than 30 meter shallow seafloor of Kueishantao Islet, Northeast offshore Taiwan Island, close to the southern Okinawa Trough. Zhejiang University, Hangzhou Dianzi University, and Taiwan Sun Yat-sen University together carried a joint investigation into seafloor hydrothermal near Kueishan island sea area and obtained continuous temperature and pH field observation data of a low-temperature hydrothermal vent (24.83414°N, 121.961 91°E) for about 87 hours. Based on Morlet complex wavelet transform method, after compared the calculating results with the recorded tidal height variance, the potential periodic relationship between temperature and pH field observed time series of shallow hydrothermal vent and tide signal can be studied. The result evidenced that tide is the main impact factor for field investigating seafloor physical and chemical parameters of white hydrothermal vent. The wavelet coefficients of the in-situ temperature and pH data after Morlet complex wavelet transform exist regular 12.9 h and 12.5 h periods. Besides, wavelet coefficients of the temperature are negative correlated with the tidal height at this semi-diurnal time scale with the correlation coefficient -0.89, and pH wavelet coefficient is the opposite case with the correlation coefficient 0.76.