Each year, typhoons (also called tropical cyclones or hurricanes) cause billions in property damage and great human toll. Besides, many typhoons occurring in tropical regions of the open ocean and their collective effects upon the marine environment and fishery remain undefined because of sampling difficulties. Recent satellite observations have shown that phytoplankton biomass can be enhanced for several days after typhoons, while in situ hydrographic observations, and data on biogeochemical properties and potential fish production induced by typhoons are limited. In this chapter, field observations are used to evaluate possible impacts of different typhoons on nutrient supply and potential fish production in the Southern East China Sea (SECS). The results provide evidence that typhoons add significantly to the nutrient supply and biological productivity in the SECS. The specific highlights are: (1) the typhoon-induced nitrate supplies after typhoons Fungwong (8.2 × 109 g N d-1) and Morakot (1.3 × 1010 g N d-1) are roughly 10-fold higher than that (1 × 109 g N d-1) during non-typhoon periods, and (2) the field observations demonstrate that typhoons can have a profound influence on nutrient supply and potential fish food sources in marginal seas.