It has been documented that the global proliferation of dam construction on the major river has reduced nutrient and sediment loading to coastal environments. As a consequence, dams can impact marine ecological systems by changing nutrient concentrations and ratios in the coastal zone. From 1998–2004, we conducted a high resolution oceanographic investigation of the East China Sea (ECS) before and after the first filling phase (June 2003) of the Three‐Gorges Dam (TGD). We found that the Si:N ratio in the River affected region changed from 1.5 in 1998 to 0.4 in 2004 with sediment loading significantly reducing (about 55%) at the Datong station after June 2003. Most importantly, we found that the PP had declined by 86% between 1998 and 2003, both measured during the high flood season. The results suggest that the ECS ecosystem may respond sensitively to changes in the nutrient supply arising from the TGD project.

The first data set of seasonal marine environment and euphotic zone integrated primary production (IP) variations in the Taiwan Strait was reported. The measured annual IP was 123 ± 86 gC m^–2 year^–1 (338 ± 235 mgC m^–2 day^–1), and its seasonal variations can be described with a left-skewed normal distribution curve. The average seasonal IP values from the highest to the lowest were summer (664 ± 270 mgC m^–2 day^–1), autumn (350 ± 118 mgC m^–2 day^–1), spring (202 ± 110 mgC m^–2 day^–1), and winter (137 ± 68 mgC m^–2 day^–1). The lowest IP was during the nutrient-rich winter because it had a short insolation duration, low incident photosynthetic active radiation (PAR) and low light transmission (shallow euphotic zone depth) due to strong vertical mixing. In contrast to the winter, the highest IP was during the nutrient-depleted summer, which had a long insolation duration, high incident PAR and high light transmission (deeper euphotic zone depth). In addition, the heterotrophic nutrients from upwelling in the south might also support the highest IP in summer. As three primary water masses exist in the Taiwan Strait and three of them have different characteristics, different mixing ratios of water masses may cause different chemical and hydrographic conditions, which leads to different levels of Chl a concentrations and primary production. It is worth to mention that offshore wind farm (OWF) construction in the Changyun Rise (CYR) of the Taiwan Strait is on-going. As primary production is the foundation for a marine ecosystem and supports the food web and fish stock, the results of this research can not only be used as the baseline for evaluating the OWF impact on the marine ecosystem but also be used for assessing their influence on fishery resources.

Dissolved primary production (DPP), particulate primaryproduction (PPP), and the subsequent bacterial production (BP) and respiration (BR) were reported for the first time in the NW Pacific. The study area of the subtropical southern East China Sea covers different water types, including oligotrophic Kuroshio and Taiwan Strait waters, as well as nutrient-rich China coastal and upwelled Kuroshio subsurface waters. On an areal basis, DPP and PPP ranged from 67–1649 and 160–1182 mgC m^–2 d^–1, respectively, showing high values in the upwelling area. The contribution of DPP to total primary production (percent extracellular release; PER) averaged 40.8 ± 12.2% with >50% in the upwelling stations. The BP and BR ranged from 48–245 and 709–2822 mgC m^–2 d^–1, respectively, showing patterns similar to those of primary production. Bacterial growth efficiency (BGE) averaged 5.7 ± 1.4%, representing the lower end of global ocean values. Phytoplankton and bacteria were well coupled in the upwelling area, whereas primary production could not sustain the bacterial carbon demand (BCD) at other stations. The slope of the log–log relationship between DPP and PPP was >1, indicating that the microbial loop may receive relatively less organic carbon supply in the future warmer, less productive ocean.