Annual variations of biotic integrity in the upper Yangtze River using an adapted index of biotic integrity (IBI)

Adaptive modification and use of Karr's index of biotic integrity (IBI) for the upper Yangtze River, including 12 metrics in five categories, have typically occurred in line with the data collected by 6-year commercial fisheries investigation. These investigations were undertaken annually in four sections of the Upper Yangtze main channel between 1997 and 2002. These four monitoring sections (Yibin - YB, Hejiang - HJ, Mudong - MD, and Yichang - YC) were selected because they represent the part of the river that will be covering a 1000 kin stretch that includes the future Three Gorges Reservoir (TGR), upstream of the Three Gorges Dam (TGD), an area influenced by the construction of TGD. in addition, historical data were used to show changes in the watershed by comparison with field investigations recently. The biotic integrity of the four sections were calculated and classified into different levels annually for recognizing its spatial and temporal variations. It was observed that IBI scores were becoming lower diminishingly since 1997 in all the four sections. Because all the data were collected before the impoundment of the Three Gorges Reservoir, it is obvious that human activities, especially over-fishing, must be crucial factor instead of damming in the upper Yangtze River in that period. (C) 2008 Published by Elsevier Ltd.

DNA polymorphism of the plankton community and its relationships to species composition in the Three Gorges Reservoir Region of the Yangtze River

We examined DNA polymorphism of the plankton community in the Three Gorges Reservoir Region of Yangtze River and studied its relationships to species composition. Samples of the plankton community were collected from nine sampling sites and analyzed by random amplified polymorphic DNA (RAPD). Nine of 60 screened primers generated a total of 88 observable 180 to 1400 by bands, all of which were polymorphic. Cluster analysis of the resulting binary format from DNA banding patterns grouped the target communities into three clusters. The topology of the constructed diagram from species composition data was generally similar to that based on RAPD markers.

Identifying paleoflood deposits archived in Zhongba Site, the Three Gorges reservoir region of the Yangtze River, China

IEECAS SKLLQG

Nutrient Dynamics in the Upwelling Area of Changjiang (Yangtze River) Estuary

Nutrient dynamics and its influence on the distribution of chlorophyll-a in the upwelling area of the Changjiang (Yangtze) River estuary were investigated in the spring (May) and summer (August) of 2004. In the spring, upwelling was apparent in the region of 122 degrees 20'-123 degrees 00' E, 31 degrees 00'-32 degrees 00' N and was associated with low temperature (16-21 degrees C), high salinity (24-33 practical salinity units [psu]), and low dissolved oxygen (2.5-6.0 mg L-1) in the upper 10 m of the water column. The spring upwelling increased the mixed-layer phosphate, nitrate, and silicate concentrations to roughly 1, 15, and 15 mu mol L-1, respectively, and improved the light transparency in the euphotic zone. This improvement in phytoplankton growing conditions was followed by an increase in chlorophyll-a concentrations. The summer upwelling was weaker and occurred over a smaller geographical area (122 degrees 20'-123 degrees 00' E, 31 degrees 15'-31 degrees 50' N). Strongly influenced by turbid Changjiang diluted water (CDW), it had little impact on the upper 10 m of the water column but instead increased nutrient concentrations at greater depths. The high concentration of particulates in the CDW reduced light transmission in the upper 10 m and, hence, limited phytoplankton growth throughout the water column. Chlorophyll-a concentrations in the summer upwelling area were roughly an order of magnitude lower than in the spring. Water clarity, as influenced by the CDW, appears to be the principal factor limiting the impact of upwelling on phytoplankton biomass in this area.

Satellite-based daily lake areas in the Yangtze Basin, China, 2000-2011

The Yangtze River Basin downstream of China's Three Gorges Dam (TGD) (thereafter referred to as "downstream" basin) hosts the largest cluster of freshwater lakes in East Asia. These lakes are crucial water stocks to local biophysical environments and socioeconomic development. Existing studies document that individual lakes in this region have recently experienced dramatic changes under the context of enduring meteorological drought, continuous population growth, and extensive water regulation since TGD's initial impoundment (i.e., June, 2003). However, spatial and temporal patterns of lake dynamics across the complete downstream Yangtze basin remain poorly characterized. Using daily MODIS imagery and an advanced thematic mapping scheme, this study presents a comprehensive monitoring of area dynamics in the downstream lake system at a 10-day temporal resolution during 2000-2011. The studied lakes constitute ~76% (~11,400 km**2) of the total downstream lake area, including the entire +70 major lakes larger than 20 km**2. The results reveal a decadal net decline in lake inundation area across the downstream Yangtze Basin, with a cumulative decrease of 849 km**2 or 7.4% from 2000 to 2011. Despite an excessive precipitation anomaly in the year 2010, the decreasing trend was tested significant in all seasons. The most substantial decrease in the post-TGD period appears in fall (1.1%/yr), which intriguingly coincides with the TGD water storage season. Regional lake dynamics exhibit contrasting spatial patterns, manifested as evident decrease and increase of aggregated lake areas respectively within and beyond the Yangtze Plain. This contrast suggests a marked vulnerability of lakes in the Yangtze Plain, to not only local meteorological variability but also intensified human water regulations from both the upstream Yangtze main stem (e.g., the TGD) and tributaries (e.g., lakes/reservoirs beyond the Yangtze Plain). The produced lake mapping result and derived lake area dynamics across the downstream Yangtze Basin provides a crucial monitoring basis for continuous investigations of changing mechanisms in the Yangtze lake system.