Comparative study on ecosystem structure and energy flow in the middle Yangtze River, China.

The ecosystem of inland river has been affected by frequent human activities. To assess the impact of waterway regulation projects on the ecosystem structure and energy flow in the middle reaches of the Yangtze River, ecological survey data were collected before and after Waterway regulation project (July 2011 and July 2015). An Ecopath model comprising 20 functional groups was constructed to quantify trophic levels (TL), ecotrophic efficiency (EE) and system-level parameters [total primary production/total respiration (TPP/TR), connectivity index (CI) and system omnivory index (SOI)], aiming to reveal the ecological disturbances induced by the waterway regulation projects. The results demonstrated that the trophic levels of the functional groups concentrated in the range of 1 to 3.3, among which the trophic level of Siniperca chuatsi was the highest (3.239 in 2011; 3.225 in 2015). Ecosystem energy flow mainly concentrated in trophic levels I and II, with level I energy flow accounting for 60.5% and 83.3% of the total in 2011 and 2015, respectively. The comparative study found that the TPP/TR value increased from 1.063 in 2011 to 3.410 in 2015, whereas the CI and SOI decreased by 0.003 and 0.015. It is concluded that the stability of the ecosystem in the middle reach of Yangtze River declined and entered an immature stage in the study period. The comparative study on ecosystem structure and energy flow would provide a guidance for the sustainable inland shipping in the Yangtze River.