Shallow water submarine hydrothermal activity: a case study in the assessment of ocean acidification and fertilization

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Most natural Shallow Water submarine Hydrothermal activates （SWH) along coastlines are related to hydrothermal eruptions involving heating of groundwater with volcanic gas. These SWHs supply nutrients to the euphotic zone, contributing to the overall natural fertility and primary productivity of coastal waters. However, SWHs also disperse toxic materials such as mercury and arsenic, and affect the acidification. We evaluate the impact of "nutrient supply" and "ocean acidification" on the primary production over the last three years in a coastal marine environment, at a SWH area discovered off Gueshandao Island, northeast Taiwan. The two types of hydrothermal vents are differentiated by color, yellow hot spring water with higher temperature >110 °C ejected from sulfur chimneys of various sizes, and colorless water with lower temperature ~80 °C ejected directly from the crevices of the andesitic bedrock. The ratios N2/Ar and 3He/4He suggest that these volcanic gases are mantle-derived. Hydrothermal fluid with pH between 2.1-3.5 erupts from the vents and affects ocean surface waters up to 1 km way. Relative to normal seawater, water around the SHW site has higher concentrations of nutrients Si and P, and micro nutrients Mn and Fe. Chlorophyll a shows high values of several tens to hundreds times greater than normal. We find forthe first time in nature that SHW enhances the growth of phytoplankton and contributes to the primary productivity of the surrounding waters.