A Ray of Light Cutting Through the Dark Pall of Flood Damages

Reference
Gong, G.-C., Liu, K.-K., Chiang, K.-P., Hsiung, T.-M., Chang, J., Chen, C.-C., Hung, C.-C., Chou, W.-C., Chung, C.-C., Chen, H.-Y., Shiah, F.K., Tsai, A.-Y., Hsieh, C.-h., Shiao, J.-C., Tseng, C.-M., Hsu, S.-C., Lee, H.-J., Lee, M.-A., Lin, I-I and Tsai, F. 2011. Yangtze River floods enhance coastal ocean phytoplankton biomass and potential fish production. Geophysical Research Letters 38: 10.1029/2011GL047519.

Noting that "huge amounts of terrigenous materials along with runoff waters are discharged to the coastal ocean during floods (Turner et al., 2006)," Gong et al. write that "the materials delivered by rivers, especially the large ones, have strong impacts on the adjacent continental shelves by enhancing primary productivity, which in turn serves as the energy source to the food chains in continental margins, where fish stocks are considerably more abundant than those in the neighboring open ocean."

Based on what they describe as their "repeated oceanographic observations" made over the past decade (1998-2010) in the East China Sea -- which they say is "renowned for its rich fishery resources (Watson and Pauly, 2001)" -- the twenty Taiwanese scientists report that they obtained important ocean productivity data for two of the most devastating floods of the Changjiang or Yangtze River of the past century (July 1998 and June to August 2010); and from these data they were able to determine the impact of the "elevated amount of terrigenous materials, including nutrients for microalgae," on the productivity of the coastal ocean and its ramifications for fish harvesting.

The researchers report that "the total algal photosynthesis rate, namely, the primary production estimated for the area of CDW [Changjiang Diluted Water] coverage observed on the 1998 cruise was 117.9 x 10³ tons C/day and that observed on the 2010 cruise was 176.0 x 10³ tons C/day," which values they say were "three times that during non-flooding periods" of intervening years. And they add that this increase in primary production "may support fisheries catch as high as 410 x 10³ tons per month, about triple the amount during non-flooding periods."

Gong et al. conclude their unique report by stating that "while the potential losses and damages caused by floods associated with the increased runoffs are being assessed, it may bring some solace to the global community considering the potential benefits the floods may generate in the form of fisheries resources in continental margins adjacent to large rivers."

Additional References
Turner, R.E., Baustian, J.J., Swenson, E.M. and Spicer, J.S. 2006. Wetland sedimentation from hurricanes Katrina and Rita. Science 314: 449-452.

Watson, R. and Pauly, D. 2001. Systematic distortions in world fisheries catch trends. Nature 414: 534-536.

Archived 4 October 2011