Wen Chen Chou

Yangtze River floods enhance coastal ocean phytoplankton biomass and potential fish production

[1]xa0The occurrence of extreme weather conditions appears on the rise under current climate change conditions, resulting in more frequent and severe floods. The devastating floods in southern China in 2010 and eastern Australia 2010–2011, serve as a solemn testimony to that notion. Accompanying the excess runoffs, elevated amount of terrigenous materials, including nutrients for microalgae, are discharged to the coastal ocean. However, how these floods and the materials they carry affect the coastal ocean ecosystem is still poorly understood. Yangtze River (aka Changjiang), which is the largest river in the Eurasian continent, flows eastward and empties into the East China Sea. Since the early twentieth century, serious overflows of the Changjiang have occurred four times. During the two most recent ones in July 1998 and 2010, we found total primary production in the East China Sea reaching 147 × 103 tons carbon per day, which may support fisheries catch as high as 410 × 103 tons per month, about triple the amount during non-flooding periods based on direct field oceanographic observations. As the frequencies of floods increase world wide as a result of climate change, the flood-induced biological production could be a silver lining to the hydrological hazards and human and property losses inflicted by excessive precipitations.

Reconciling the paradox that the heterotrophic waters of the East China Sea shelf act as a significant CO2 sink during the summertime: Evidence and implications

[1]xa0To explore the paradox that the heterotrophic waters of the East China Sea (ECS) shelf act as a significant CO2 sink in summer, vertical structures of carbon chemistry and hydrography were examined in July 2007. The results show that waters above the pycnocline (∼10 to 30 m) in the major CO2 sink area are supersaturated with oxygen (110 ± 7%; autotrophic) but undersaturated with respect to atmospheric CO2 (ΔfCO2 = −130 ± 58 μatm; sink). In contrast, waters below the pycnocline are undersaturated with respect to oxygen (61 ± 16%; heterotrophic) but supersaturated with CO2 (ΔfCO2 = 116 ± 115 μatm; source). This demonstrates that summer stratification is the key factor maintaining the CO2 sink status in the heterotrophic ECS shelf waters. Furthermore, the shallow pycnocline can easily be broken down when strong mixing occurs, potentially allowing the respired CO2 stored in the subsurface waters to return to the atmosphere.

Nutrient supply in the Southern East China Sea after Typhoon Morakot

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Elevated particulate organic carbon export flux induced by internal waves in the oligotrophic northern South China Sea

To understand the biogeochemical response to internal waves in the deep basin of the northern South China Sea (NSCS), particulate organic carbon (POC) export fluxes were quantified for the first time during the passage of large internal waves using drifting sediment traps attached with hydrographic sensors. Results revealed large variations in temperature, nitrate and chlorophyll a (Chl a) concentrations during and after internal waves, suggesting that cold nutrient-replete waters may be brought to the euphotic zone in the dissipation zone during and after the passage of internal wave packets, resulted in phytoplankton flourished. Most importantly, POC export fluxes (110.9u2009±u200910.7u2009mgu2009C m−2 d−1) were significantly enhanced after internal waves compared to non-internal wave area (32.6–73.0u2009mgu2009C m−2 d−1) in the NSCS. Such elevated POC fluxes may be induced by downward flourished biogenic particles, particle aggregation or converged particles from mixed layer triggered by internal waves.

Corrigendum to “Nutrient supply in the Southern East China Sea after Typhoon Morakot”

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