Implications of eutrophication for biogeochemical processes in the Three Gorges Reservoir, China
Three Gorges Reservoir, the largest man-made lake in the Changjiang River traps a small fraction of the nitrogen (N) and dissolved silicate (DSi) inflows, and a larger fraction of P. This leads to distortion of downstream nutrient ratios, with increased risk of harmful algal blooms.
Biogeochemical nutrient trap
The Three Gorges Reservoir acts as a trap for biogenic silica, not for dissolved silicate. This is due to dissolution of sediment BSi, which compensates for DSi retention by primary diatom production. Transformations of reactive N cause an increase of the dissolved inorganic nitrogen (DIN) load by 3% during transport through the TGR, while retention of dissolved inorganic phosphorus (DIP) is enhanced by biological production.
Changing nutrient ratios
As a result, the TGR causes an increase of the molar DIN/DSi, DSi/DIP, and DIN/DIP ratios, and a decrease of DIN/RSi (reactive Si, the sum of DSi and BSi), leading to an enhanced phosphorus and silica limitation downstream of the TGR. The overall impact of the changing stoichiometry as expressed by the Index for Coastal Eutrophication Potential (ICEP) is an excess production of 27 Tg C/year of nondiatom, potentially harmful phytoplankton. More intensive monitoring is thus needed to better understand the biogeochemical processes in the TGR and to support policy development aimed at improving the water quality in the Changjiang River.
Authors
Specifications
- Publication title
- Implications of eutrophication for biogeochemical processes in the Three Gorges Reservoir, China
- Publication date
- 14 July 2018
- Publication type
- Publication
- Magazine
- Regional Environmental Change
- Product number
- 3350